The analogy of Being in in the thought of St. Thomas.

b’Subject: Philosophy’
b’Topic: The analogy of Being in in the thought of St. Thomas.’
b’First, I need the paper topic proposal by Wednesday, October 6. (1 page = 300 words). Please read some notes from my course (attached) to make a proposal.\nSecondly, I need a complete paper by October 24\nRequirement of paper:\nI. Research paper: Each student is to write a scholarly research paper. The paper is to be no less than 16 pp. and no more than 20 pp., double spaced, 12 point font, 1.0 inch margins all around. The paper should involve substantial engagement with secondary literature concerning Thomistic metaphysics. \nII. Students are to submit a paper topic proposal (by Wednesday, October 6), \n\nIII. All citations of primary texts must be made with reference to a printed edition. Apart from abbreviated references to primary texts of Aristotle, Aquinas, et al. (in accordance with scholarly convention in recent philosophical publication), all points of style should follow Kate L. Turabian, A Manual for Writers of Research Papers, Theses, and Dissertations, 9th edition (Chicago: University of Chicago, 2018). Failure to follow these guidelines, either on the review draft or on the final draft, will make the maximum possible granyzde on that draft a B+.’

Carl: Metaphysics 1
Metaphysics: Fall 2020
Brian Thomas Carl, Ph.D.
Center for Thomistic Studies
Schedule of Topics & Readings
A. What is Metaphysics?
0. Introduction to the Study of Metaphysics: Wippel 3-22, In Met. pr.
1. The knowledge of being: Wippel 23-44, In DT 5.3
2. Separatio and the knowledge of being as being: Wippel 44-62, In DT 5.3
B. Being and beings: Analogy and Participation
3. The one and the many: Wippel 65-73
4. Analogy I: the meaning of analogy and the “horizontal” analogy: Wippel 73-93
5. Participation: Wippel 94-131
C. The Composite Character of Ens Commune
6. Real composition and distinction of essence and esse: Wippel 132-161
7. Substance-accident composition: Wippel cc. 7-8, esp. pp. 197-228, 253-61
8. Matter-form composition in corporeal substances: Wippel c. 9, esp. 312-327, 351-75
9. Comparison and coordination of the modes of composition: potency and act
D. Transcendentals
10. The transcendentals: DV 1.1; In Met. 4.2, 10.3; ST 1.16.1-4; ST 1.5.1-4
E. Natural Theology I: God’s Existence
11. How God is known through natural reason: ST 1.2.1-2
12. Argumentation for God’s existence: the first way: ST 1.2.3, Wippel 444-59
F. Natural Theology II: Knowing and Naming God
13. Simplicity: God as ipsum esse per se subsistens: ST 1.3.1-8
14. Establishing divine perfection: ST 1.4.1-3
15. Divine naming: the threefold way: ST 1.12
16. Analogy II: “transcendental” analogy and divine names: ST 1.13
17. Divine operations: intellect, will, power: ST 1.14, 1.19, 1.25
Carl: Metaphysics 2
ABBREVIATIONS
CT Compendium theologiae
De ente De ente et essentia
De prin. De principiis naturae
De malo Quaestiones disputatae de malo
De pot. Quaestiones disputatae de potentia Dei
De spirit. creat. Quaestio disputata de spiritualibus creaturis
De ver. Quaestiones disputatae de veritate
In De an. Sententia libri De anima
In DN In librum Beati Dionysii De divinis nominibus expositio
In DT / SBDT Super Boetium de Trinitate
In Ethic. Sententia libri Ethicorum
In Meta. In duodecim libros Metaphysicorum Aristotelis expositio
In Per. Expositio libri Peryermenias
In Phys. In octos libros Physicorum Aristotelis expositio
In Post. Expositio libri Posteriorum
In Sent. Scriptum super libros sententiarum magistri Petri Lombardi
LR Lectura romana in primum Sententiarum Petri Lombardi
Quodl. Quodlibeta
Resp. (108) Responsio ad magistrum Ioannem de Vercellis de 108
articulis
SCG Summa contra Gentiles
ST Summa theologiae
Carl: Metaphysics 3
1. The Knowledge of Being
As already indicated, metaphysics is the philosophical science that studies being, or, to be
more precise, being as being. What does this mean? It will be the purpose of the first two sections
of the course to begin to address this question. We will begin with a consideration of the following
question: how is being known by human beings?
1.1. Background: Apprehension and Judgment
In order to understand the Thomistic position concerning the knowledge of being, it is
necessary first to recall the distinction, drawn in logic (as well as in the study of human nature and
in epistemology), between apprehension and judgment as two of the three operations (along with
reasoning) of the human intellect.
Apprehension
By the act of apprehension, the human intellect grasps the quiddity or essence of a
(corporeal) reality: this is to say that the intellect grasps what something is. We can consider a text
from St. Thomas’s early De ente et essentia, c. 1, for a treatment of what he means by the term
quiddity:
Et quia illud per quod res constituitur in proprio
genere vel specie est hoc quod significatur per
diffinitionem indicantem quid est res, inde est
quod nomen essentiae a philosophis in nomen
quidditatis mutatur; et hoc est etiam quod
Philosophus frequenter nominat quod quid erat
esse, id est hoc per quod aliquid habet esse quid.
Dicitur etiam forma, secundum quod per formam
significatur certitudo uniuscuiusque rei, ut dicit
Avicenna in II Metaphisicae suae. Hoc etiam alio
nomine natura dicitur, accipiendo naturam
secundum primum modum illorum quatuor quod
Boetius in libro De duabus naturis assignat:
secundum scilicet quod natura dicitur omne illud
quod intellectu quoquo modo capi potest, non enim
res est intelligibilis nisi per diffinitionem et
essentiam suam; et sic etiam Philosophus dicit in V
Metaphysicae quod omnis substantia est natura.
Tamen nomen naturae hoc modo sumptae videtur
significare essentiam rei secundum quod habet
ordinem ad propriam operationem rei, cum nulla
And since that through which a thing is constituted
in its proper genus or species is what is signified
through the definition indicating what the thing is,
therefore the name of essence was changed by
philosophers to the name “quiddity”; and this is
also what the Philosopher frequently calls “the
what it was to be,” that is, that through which
something has a [certain] kind of being. It is also
called form, inasmuch as through form the reality
of any thing is signified, as Avicenna says in Book
II[I] of his Metaphysics. This is also by another
name called the nature, taking nature according to
the first meaning of the four which Boethius
assigns in the book Of [the Person and] the Two
Natures: according to the way, namely, that
everything which can be received in any way by
the intellect is called nature, for a thing is not
intelligible except through its definition and
essence; and thus the Philosopher also says in
Book V of the Metaphysics that every substance is
a nature. Nevertheless the name of nature taken in
Carl: Metaphysics 4
res propria operatione destituatur; quidditatis vero
nomen sumitur ex hoc quod per diffinitionem
significatur. Sed essentia dicitur secundum quod
per eam et in ea ens habet esse.
this way seems to signify the essence of a thing
insofar as it has an order to the proper operation of
the thing, since no thing lacks its proper operation;
but the name of quiddity is taken from what is
signified through the definition. But it is called
essence insofar as through it and in it a being has
[the act of] being.
-Quiddity comes from quid est, what-it-is
-Essence is the term used to translate Aristotle’s to ti en einai, the what-it-was-to-be (also
sometimes rendered in Latin as quod quid erat esse)
-form and nature are other terms that can signify what is signified by the term quiddity, but
they do so with different connotations
The quiddity or essence that is grasped by the act of apprehension is expressed through a
definition: that is, a definition is the sign of what is grasped in the act of apprehension, just as a
single word is a sign of something understood. Unlike a single word, a definition is complex in the
sense that it is composed of several words: nevertheless, a definition is simple in the sense that it
expresses one apprehended quiddity. So, for example, one expresses what one grasps in the
apprehension of the quiddity of a triangle through the definition, “three sided planar figure.” In
apprehending a quiddity, one knows a thing as it is distinct from other things, and this is why
knowledge of a quiddity is expressed through a definition, which takes the typical form of a genus
and difference.1
The apprehension of a given quiddity can be more or less distinct, as for example one
might know a horse or a dog only as an animal rather than as distinct from other animals. St.
Thomas observes that in such a case, one knows the quiddity “animal” less distinctly too, because
one knows a universal whole more distinctly when one knows its parts, i.e., the species contained
within it (ST 1.85.3):
Manifestum est autem quod cognoscere aliquid in
quo plura continentur, sine hoc quod habeatur
propria notitia uniuscuiusque eorum quae
continentur in illo, est cognoscere aliquid sub
confusione quadam. . . . Cognoscere autem
distincte id quod continetur in toto universali, est
habere cognitionem de re minus communi. Sicut
cognoscere animal indistincte, est cognoscere
animal inquantum est animal, cognoscere autem
But it is manifest that to know something in which
many things are contained, without having a proper
knowledge of each of those things which are
contained in it, is to know something under a
certain confusion. . . . But to know distinctly that
which is contained in a universal whole is to have
knowledge of a less common thing. Just as to know
animal indistinctly is to know animal insofar as it
is animal; but to know animal distinctly is to know
1SCG 3.46: “But through knowing about a thing what it is, the thing is known just as it is distinct from other
things: therefore also a definition, which signifies what a thing is, distinguishes the definitum from all
other things.” [“Per hoc autem quod scitur de re quid est, scitur res prout est ab aliis distincta: unde et
definitio, quae significat quid est res, distinguit definitum ab omnibus aliis.”]
Carl: Metaphysics 5
animal distincte, est cognoscere animal inquantum
est animal rationale vel irrationale, quod est
cognoscere hominem vel leonem. Prius igitur
occurrit intellectui nostro cognoscere animal quam
cognoscere hominem, et eadem ratio est si
comparemus quodcumque magis universale ad
minus universale.
animal insofar as it is rational or irrational animal,
which is to know man or lion: therefore it first
happens to our intellect to know animal before it
knows man: and it will be the same if we compare
whatever is more universal to what is less
universal.
In general, human knowledge proceeds from the more universal to the less universal: one
distinguishes animal before one distinguishes particular species of animal.2 There is thus progress
in one’s apprehension of any given quiddity, as one proceeds from a more universal and confused
grasp of that quiddity to a clearer knowledge of that quiddity as it is distinct from others.
Judgment
By the act of judgment—also called composition and division—the human intellect
combines and separates the indivisible intelligibles known through the act of apprehension. For
example, the judgment that the dog is white involves both the quiddity “dog” (a substance) and the
quiddity “white” (a quality). Judgment as an act thus depends upon the act of apprehension: one
cannot judge that something is such and such without some apprehensive grasp of the parts of the
judgment. In this instance, as in others, what is complex must be reduced to what is simple.
According to Aristotle, truth and falsity arise only in judgment, rather than in the
apprehension of indivisibles. By apprehension, one only knows what something is, and to fail to
know what something is is to be in a state of ignorance rather than falsity. But when one judges
that something is the case, then there can be truth or falsity about one’s intellectual act.3
In addition to the quiddities that are linked or divided in a judgment, there is the verb
copula itself—is or is not—which expresses the very composition or division of the judgment. In
speech, the most common use of the verb to be is in order to express the intellectual act of
judgment. This provides an important clue concerning the answer to our question about how it is
that the intellect knows being: we will now examine an answer to this question.
1.2. The Knowledge of Being (or Existence)
Given the distinction between apprehension and judgment as operations of the human
intellect, the question arises whether the human intellect knows being through the former or the
latter. As indicated above, the apprehension of a thing’s quiddity can be more or less distinct,
according to a greater or lesser degree of universality. A dog can be understood more generally as
an animal, or as a living thing, or as a body, or as a substance. These levels of increasingly greater
universality about the knowledge of one being, a dog, might suggest that the knowledge of being is
itself acquired through apprehension: according to this suggestion, being would be the most
general quiddity or essence, a most general universal under which all the objects known by the
human intellect would fall.
2See Physics 1.1: “Similarly a child begins by calling all men ‘father,’ and all women ‘mother,’ but later on
distinguishes each of them.”
3This will be explored in greater depth in our treatment of truth (during our study of the transcendentals) later
in the semester.
Carl: Metaphysics 6
However, there is a problem with this suggestion that being is simply the most universal
object of the act of apprehension. As we will explain below (among other places, in discussion of
the analogical character of being), it cannot be the case that being is a genus.4 But if being cannot
be a genus, then it cannot be the case that one arrives at one’s knowledge of being just through the
kind of abstraction involved in the act of apprehension. How then does a human being know
being?
To prepare for our consideration of this question, it will be helpful to briefly consider some
of the Latin terminology used by St. Thomas. Several different Latin terms associated with the
verb esse, which might all be translated into English as ‘being,’ have subtly distinct meanings in the
Latin. In this instance, an awareness of the Latin terminology serves to enrich understanding in a
crucial way. Therefore, throughout this course I will make frequent reference to these terms in the
Latin. It should be noted that even in this first section of the notes, the term being has already been
used in ways that are distinguished in Latin.
esse – the infinitive, “to be”; can be translated as being, the act of being, or existence
ens – the present participle of esse; typically used to refer to a concrete being
essentia – almost exclusively translated as essence, although sometimes as being
St. Thomas’s answer to the question raised is that it is through the intellect’s second act that
being, in the sense of a thing’s actual existence, is known. Or, to put it in another way, it is through
the intellect’s second act that there is a grasp of real being: the judgment expressed as “the thing is”
is the expression of the mind’s grasp of the real being of the thing. St. Thomas sets forth this view
in a number of texts. For example, in DT, 5.3, he begins by stating the distinction between
apprehension and judgment, the intellect’s first and second operations:
Sciendum est igitur quod secundum philosophum
in III de anima duplex est operatio intellectus. Una,
quae dicitur intelligentia indivisibilium, qua
cognoscit de unoquoque, quid est. Alia vero, qua
componit et dividit, scilicet enuntiationem
affirmativam vel negativam formando.
Et hae quidem duae operationes duobus, quae sunt
in rebus, respondent. Prima quidem operatio
respicit ipsam naturam rei, secundum quam res
intellecta aliquem gradum in entibus obtinet, sive
sit res completa, ut totum aliquod, sive res
incompleta, ut pars vel accidens. Secunda vero
We must realize, therefore, that as the Philosopher
says (De anima III) the operation of the intellect is
twofold: one, which is called the “understanding of
indivisibles,” by which it knows what a thing is.
But another, by which it composes and divides,
that is, by forming affirmative and negative
statements.
And these two operations correspond to two
[principles] in things. The first operation concerns
the nature of a thing, in virtue of which the thing
understood holds a certain rank among beings,
whether it be a complete thing, like some whole, or
an incomplete thing, like a part or an accident. But
4As will be discussed below, the reason for this is that any genus must be divided by differences taken from
outside the genus. If being were a genus, therefore, it would need to be divided by differences taken from
outside of being: but this is impossible, because whatever would be outside the genus of being would be
non-being, which is nothing.
Carl: Metaphysics 7
operatio respicit ipsum esse rei, quod quidem
resultat ex congregatione principiorum rei in
compositis vel ipsam simplicem naturam rei
concomitatur, ut in substantiis simplicibus.
the second operation concerns the very being of a
thing, which results from the union of the
principles of a thing in composite [substances], or
accompanies the thing’s simple nature, as in simple
substances.
The crucial claim here is that it is the intellect’s second operation that concerns the very
being of a thing: secunda operatio respicit ipsum esse rei. How should we understand this claim?
We need to consult a text in which St. Thomas comments on the meaning of the term esse. In In
Sent. 1.33.1.1 ad 1, St. Thomas explains that the term esse can be understood in three ways:
Sed sciendum, quod esse dicitur tripliciter. Uno
modo dicitur esse ipsa quidditas vel natura rei,
sicut dicitur quod definitio est oratio significans
quid est esse; definitio enim quidditatem rei
significat. Alio modo dicitur esse ipse actus
essentiae; sicut vivere, quod est esse viventibus,
est animae actus; non actus secundus, qui est
operatio, sed actus primus. Tertio modo dicitur
esse quod significat veritatem compositionis in
propositionibus, secundum quod “est” dicitur
copula: et secundum hoc est in intellectu
componente et dividente quantum ad sui
complementum; sed fundatur in esse rei, quod est
actus essentiae, sicut supra de veritate dictum est.
But it must be known that esse is said in three
ways. In one way esse expresses the very quiddity
or nature of a thing, as it is said that a definition is
an expression signifying what a being (esse) is; for
a definition signifies the quiddity of a thing. In
another way esse expresses the very act of an
essence; such as “to live,” which is esse in living
things, is the act of the soul; not second act, which
is operation, but first act. In a third way esse is said
as what signifies the truth of composition in
propositions, according to which “is” is called the
copula; and in this sense [esse] with regard to its
completion is in the intellect composing and
dividing; but this [esse in the mind] is founded
upon the esse of a thing, which is the act of an
essence, as was said above about truth.
Esse can mean:
(1) the quiddity of a thing
(2) the act of an essence
(3) the truth of composition as expressed in a proposition by the copula, “is”
So, in the text from the De Trinitate, when St. Thomas says that the intellect’s second
operation concerns the very esse of a thing, in which of these three senses should ipsum esse rei be
taken? It is evident by that by this St. Thomas does not mean a thing’s quiddity, because he has just
clarified that the quiddity of a thing is known by the intellect’s first operation. But he also cannot
mean by esse the truth of composition, because esse in this sense is in the intellect rather than in
things. Furthermore, as St. Thomas indicates in this text from the Sentences Commentary, esse in
the third sense is founded upon esse in the second sense, the act of an essence.
Carl: Metaphysics 8
Thus, by ipsum esse rei, St. Thomas must mean what he has called the act of an essence.
But what is it for an essence to be actual? This is just for it to be, in the sense of existence. It is for
this reason that many recent Thomistic scholars understand the ipsum esse rei that is grasped by the
mind’s second operation to be the existence of the thing.5
We can further clarify this claim, that judgment concerns the esse of a thing, by noting that
there are two kinds of judgments: (1) judgments of attribution and (2) judgments of existence.6 The
example of judgment given earlier—the dog is white—is an example of the former, in which
something is predicated of (or divided from) a subject through the verb copula. But one can also
form the judgment the dog is, that is, the dog exists. This is a judgment of existence, in which
nothing other than the actual existence of the subject is expressed. That a judgment of existence is
possible should serve as an indication that esse in the sense of existence is grasped through the
second operation of the mind.7
Resolution/Analysis and the Apprehensive Grasp of Being
Complementing this text from the Super Boetium De Trinitate 5.3, in many other places St.
Thomas speaks of the knowledge of being (ens) in terms of apprehension, frequently citing
Avicenna, as in the following example from DV 21.4 ad 4:
Cuius ratio est, quia illud quod primo cadit in
apprehensione intellectus, est ens. . . .
The reason for this is because that which first falls
into the apprehension of the intellect is being. . . .
It should be noted that Thomas cites this same principle early in the Super Boetium De
Trinitate itself (DT 1.3 obj. 3), so that it should not in itself be interpreted as contradicting what has
been said about the role of judgment in knowing being in the sense of esse. Just what does St.
Thomas means by this primacy of being (ens) in the order of apprehension? We can turn to another
text in which Thomas cites this Avicennian axiom (ST 1-2.94.2):
In his autem quae in apprehensione omnium
cadunt, quidam ordo invenitur. Nam illud quod
primo cadit in apprehensione, est ens, cuius
intellectus includitur in omnibus quaecumque quis
apprehendit. Et ideo primum principium
indemonstrabile est quod non est simul affirmare et
negare, quod fundatur supra rationem entis et non
entis, et super hoc principio omnia alia fundantur,
ut dicitur in IV Metaph.
But among those things that fall under the
apprehension of all [men], a certain order is found.
For that which first falls into the apprehension is
being, the understanding of which is included in
everything whatsoever that someone apprehends.
And therefore the first indemonstrable principle is
that there is not simultaneous affirmation and
negation, which is founded upon the meaning of
being and non-being; and upon this principle are
founded all the other [principles], as is said in
Metaphysics IV. (ST 1-2.94.2)
5For example, this is the position of Gilson, Fabro, Owens, and Wippel, and their various followers.
6For St. Thomas’s acknowledgment of this distinction, see In Per. 2.2.
7As we will see later in the course, a judgment of attribution also grasps the esse of the thing, according to its
composite character. St. Thomas claims that truth obtains in the intellect’s second operation because
Carl: Metaphysics 9
Here St. Thomas relates the primacy of the principle of non-contradiction to the primacy of
the apprehension of being (ens). What does this text mean by the primacy of the apprehension of
being? Does this not contradict the claim made in DT 5.3 that it is the intellect’s second operation
that grasps ipsum esse rei? To answer this question, we need to do two things: (1) give an account
of the relationship between the terms ens and esse, and (2) briefly discuss the notion of resolution
or analysis (resolutio).
(1) Regarding ens and esse: St. Thomas typically uses the term ens to refer to a being (in
the sense of a concrete being), and he with some frequency clarifies or explains the notion of ens as
id quod est (that which is) or habens esse (something having existence) or quod habet esse (what
has existence).8 It can be said that ens taken in this sense is the most indistinct and universal way in
which any existing thing can be apprehended. That is, it is always possible to apprehend a given
thing as a being (ens)—but it should be noted that one’s grasp of any existing thing known through
sense experience will always have some quidditative content more specific than “being.” In other
words, it will never the case that one can only say (about a given concrete thing known through
sense experience) that it is a being (ens).
However, this apprehensive grasp of ens depends upon the prior grasp of esse through the
intellect’s second operation: this is why the notion of ens is rightly explained as quod habet esse.
The concept of ens can therefore be called a complex concept, insofar as the apprehension of ens
depends upon the intellect’s grasp of esse through its second operation.
(2) Regarding the notion of resolution: whatever is complex and posterior must, according
to St. Thomas, be resolved into that which is simple and prior. Resolutio is the intellectual process
according to which one moves from the posterior to the prior. It is for this reason that it is often
translated into English as analysis. Insofar as the whole project of Aristotelian science is to proceed
from that which is posterior and better known to us to that which is prior and more knowable in
itself, science itself can be characterized as a project of resolution.
St. Thomas distinguishes resolution into two kinds: (a) resolution secundum rem and (b)
resolution secundum rationem. As Msgr. Wippel explains, according to the former kind of
resolution one seeks the extrinsic causes of a given thing; while according to the latter kind of
resolution one examines the intrinsic causes (particularly the formal cause) of the thing, proceeding
from the less universal to the more universal. It is therefore in the order of resolution secundum
rationem that one arrives at being (ens) as the most universal concept according to which a given
thing may be understood.
When it is said that something is first or prior, one must always ask the following question:
Is this priority in time, or in causality, or in the order of resolution, or in some other way? That is,
just because something is said to be first or to be before something else, this does not mean that it
is first temporally or even causally. In the case of the Avicennian axiom that being is what first falls
into the apprehension of the intellect, the “first” here should not be interpreted in a strictly
temporal way; rather, as Msgr. Wippel argues, St. Thomas seems to be referring to priority in the
order of resolution. Being (ens) is that into which whatever the intellect conceives can be resolved.
8See Wippel 33 n. 35 for a selection of references.
Carl: Metaphysics 10
2. Separatio and the Discovery of Being as Being
What we have established up to this point is that, for St. Thomas, esse in the sense of
existence is grasped through the second operation of the intellect. This grasp of esse through
judgment is attained by virtually all human beings: anyone who can understand the meaning of a
proposition of the form “x exists” grasps esse in the sense of actual existence. We have said before
that metaphysics is the science that studies being as being: is esse in the sense of existence—or,
alternatively, ens as that which is—what we mean by this expression, “being as being?”
2.1. The Distinction of the Subject of a Speculative Science: Division of the Sciences
To answer this question, we need to consider the character of the subject of a speculative
science. Every science studies being, because whatever can be known by the human intellect is
always a being.9 The subject of each of the chief speculative sciences (physics, mathematics, and
metaphysics) is distinguished by the mind as a general object of speculation. “Being” taken
generally is not in any way a distinct object of speculation, because every object of human
speculation is a being. Whether one studies dogs, triangles, or words—distinct objects of
speculation—whatever one studies must be a being. So it cannot be that being, either in the sense
of existence (esse) or in the sense of that which is (ens), is the precise subject of metaphysics.
How are the subjects of the chief speculative sciences distinguished? St. Thomas explains
in Super Boetium De Trinitate 5.1 that “the speculative sciences must be divided according to
differences between objects of speculation, considered precisely as such.”10 Now, whenever the
intellect knows an object of speculation, it does so by virtue of an immaterial likeness of the
known existing in the intellect: fundamentally, the activity of intellectual cognition is immaterial in
character.11 This leads St. Thomas to observe that an object of speculation “considered precisely as
such” is separate from matter and motion; and thus the differences among objects of human
speculation will be established by the differing degrees according to which those objects are
separate from matter and motion.
St. Thomas therefore characterizes the distinction among the objects of the chief
speculative sciences in the following way:
science object’s degree of separation from matter
physics can neither exist without matter nor be understood without matter
mathematics can not exist without matter, but can be understood without matter
metaphysics can exist without matter
The objects studied by philosophical physics (i.e., natural philosophy) can neither exist
without matter nor be understood without matter. For example, it pertains to natural philosophy to
study human nature, and: (1) human beings do not exist except in matter, and (2) one does not
understand what a human being is without knowing that a human being has flesh and bones, i.e.,
particular kinds of matter. As a science, natural philosophy does abstract from particular matter (for
example, this flesh and these bones) but not from matter taken universally. It is for this reason that
9The philosophical thesis positing the connection between being and intelligibility can be traced through
Plato to Parmenides. It is a position generally taken for granted by Aristotle.
10In DT 5.1 [Leon. 50.138]: “. . . et ideo oportet scientias speculativas dividi per differentias speculabilium in
quantum speculabilia sunt.”
11This will be a claim familiar to students who have taken courses in the Thomistic philosophy of human
nature or in Thomistic epistemology.
Carl: Metaphysics 11
St. Thomas characterizes the degree of abstraction peculiar to natural philosophy as the abstraction
of the universal from the particular rather than as the abstraction of form from matter.
By contrast, mathematics studies objects that cannot exist without matter, even though they
can be understood without matter. For example, extension (continuous quantity) or a triangle
(which is a shape, a quality) can only actually exist in a material substrate. Nevertheless, one’s
study of such mathematical objects need not make any reference to matter: in other words,
mathematics as a study makes no reference to material causes. Mathematical objects are abstracted
in this way just because they do not exist only in a particular kind of matter: for example, a triangle
can be made of bronze or of wood, without any difference in its properties qua triangle. Because of
the more abstract character of mathematical objects, St. Thomas characterizes this degree of
abstraction as the abstraction of form from matter.
The objects studied in metaphysics are separate from matter to a greater degree, in that
they are capable of existing without matter. St. Thomas lists among the objects studied by
metaphysics such examples as substance, quality, act, potency, one and many. The objects studied
by metaphysics are immaterial in this precise sense: they need not exist in matter. For this reason
the objects studied by metaphysics can be said to be negatively or neutrally immaterial, as opposed
to what is positively immaterial (as for example angels or God).12
2.2. Separatio and the Discovery of the Subject of Metaphysics
From what has been said, it is clear that esse taken in the sense of actual existence is not
the subject of metaphysics. A person can grasp the notion of existence without grasping being as
something that does not depend upon motion and matter: but it is being understood in just this
latter way that is the subject of metaphysics. How then is the subject of metaphysics known? The
objects of physics are known by abstraction of the universal from the particular; the objects of
mathematics are known by the abstraction of form from matter. What of the subject of
metaphysics?
According to St. Thomas, being as being is not known through just any judgment, but
rather through a special kind of judgment which he terms separation (separatio). In this section of
our course, we will examine his comments concerning this judgment. This will effectively be an
extended commentary on the closing section of the In DT 5.3. (I am providing Fr. Armand Maurer’s
translation of this key text.)
Sic ergo intellectus distinguit unum ab altero aliter
et aliter secundum diversas operationes; quia
secundum operationem, qua componit et dividit,
distinguit unum ab alio per hoc quod intelligit
unum alii non inesse. In operatione vero qua
intelligit, quid est unumquodque, distinguit unum
ab alio, dum intelligit, quid est hoc, nihil
intelligendo de alio, neque quod sit cum eo, neque
quod sit ab eo separatum. Unde ista distinctio non
Accordingly, through its various operations the
intellect distinguishes one thing from another in
different ways. Through the operation by which it
composes and divides, it distinguishes one thing
from another by understanding that the one does
not exist in the other. Through the operation,
however, by which it understands what a thing is, it
distinguishes one thing from another by knowing
what one is without knowing anything of the other,
12This is the language used by Msgr. Wippel. See Wippel 44.
Carl: Metaphysics 12
proprie habet nomen separationis, sed prima
tantum. Haec autem distinctio recte dicitur
abstractio, sed tunc tantum quando ea, quorum
unum sine altero intelligitur, sunt simul secundum
rem.
either that it is united to it or separated from it. So
this distinction is not properly called separation,
but only the first. It is correctly called abstraction,
but only when the objects, one of which is known
without the other, are one in reality.
Separation is the act by which one understands “that one does not exist in the other.” It
therefore differs from abstraction, properly speaking, because abstraction always involves the
mental separation of things that are one in reality (such as the universal and the particular, or form
and matter). While abstraction in this strict sense13 is according to the intellect’s first operation
(because to name a universal abstracted from the particular or a form abstracted from matter is to
state what something is), separation in the strict sense delineated here is according to the intellect’s
second operation, which is judgment. St. Thomas elaborates on this claim about separation as
opposed to abstraction later in q. 5 a. 3:
In his autem quae secundum esse possunt esse
divisa, magis habet locum separatio quam
abstractio. Similiter autem cum dicimus formam
abstrahi a materia, non intelligitur de forma
substantiali, quia forma substantialis et materia sibi
correspondens dependent ad invicem, ut unum sine
alio non possit intelligi, eo quod proprius actus in
propria materia fit. Sed intelligitur de forma
accidentali, quae est quantitas et figura, a qua
quidem materia sensibilis per intellectum abstrahi
non potest, cum qualitates sensibiles non possint
intelligi non praeintellecta quantitate, sicut patet in
superficie et colore, nec etiam potest intelligi esse
subiectum motus, quod non intelligitur quantum.
Substantia autem, quae est materia intelligibilis
quantitatis, potest esse sine quantitate; unde
considerare substantiam sine quantitate magis
pertinet ad genus separationis quam abstractionis.
But in the case of things that can exist separately,
separation rather than abstraction obtains.
Similarly, when we say form is abstracted from
matter, we do not mean substantial form, because
substantial form and the matter correlative to it are
interdependent, so that one is not intelligible
without the other, because the appropriate act is in
its appropriate matter. Rather, we mean the
accidental forms of quantity and figure, from
which indeed sensible matter cannot be abstracted
by the intellect, because sensible qualities cannot
be understood unless quantity is presupposed, as is
clear in the case of surface and color. And neither
can we understand something to be the subject of
motion unless we understand it to possess quantity.
Substance, however, which is the intelligible
matter of quantity, can exist without quantity.
Consequently, the consideration of substance
without quantity belongs to the order of separation
rather than to that of abstraction.
13I add the qualification “in the strict sense” here because at times St. Thomas uses the term abstraction more
generally so as to include both abstraction in the strict sense (which is according to the intellect’s first
operation) and separation (which is according to the intellect’s second operation).
Carl: Metaphysics 13
St. Thomas begins by discussing the abstraction of mathematical objects. He notes that
when it is said that one abstracts form from matter, this does not mean that one abstracts the
substantial form from matter—such an abstraction is not possible, because a corporeal substance is
not intelligible apart from its appropriate matter. Rather, what one abstracts in mathematics are
quantities and figures (a kind of quality), which do not depend upon a particular kind of matter for
their existence. (That is, they can exist in bronze, in wood, etc., which are different kinds of
substance.)
These quantitative and qualitative forms are therefore abstracted from what St. Thomas
calls sensible matter, by which he means material things insofar as they are known through their
sensible qualities. It is possible to abstract quantity and figure from sensible matter because the
latter presupposes the former for its very intelligibility: for example, one cannot understand color
(a sensible quality) without knowing that it is an accident of a surface. However, one does not
abstract quantity or figure from matter absolutely, because quantity and figure are always accidents
of a substance. By the phrase intelligible matter, St. Thomas means the matter that “exists in
sensible things, but not insofar as they are sensible.”14 Intelligible matter is grasped only by the
intellect, which grasps substance as what underlies all accidents. When one abstracts mathematical
objects (such as a triangle), one does not abstract from matter absolutely, but only from sensible
matter.
Thus, although quantity cannot exist without an underlying substance15, substance can
exist without quantity. However, one does not recognize this truth by virtue of any abstraction by
the intellect. Rather, it is by virtue of what St. Thomas above called separation—an instance of the
intellect’s second operation—that one judges that substance is not of itself quantified. To consider
substance in this way, as without quantity, “belongs to the order of separation rather than to that of
abstraction.”
Sic ergo in operatione intellectus triplex distinctio
invenitur. Una secundum operationem intellectus
componentis et dividentis, quae separatio dicitur
proprie; et haec competit scientiae divinae sive
metaphysicae. Alia secundum operationem, qua
formantur quiditates rerum, quae est abstractio
formae a materia sensibili; et haec competit
mathematicae. Tertia secundum eandem
operationem quae est abstractio universalis a
particulari; et haec competit etiam physicae et est
communis omnibus scientiis, quia in scientia
praetermittitur quod per accidens est et accipitur
quod per se est. Et quia quidam non intellexerunt
differentiam duarum ultimarum a prima, inciderunt
We conclude that there are three kinds of
distinction in the operation of the intellect. There is
one through the operation of the intellect joining
and dividing which is properly called separation;
and this belongs to divine science or metaphysics.
There is another through the operation by which
the quiddities of things are conceived which is the
abstraction of form from sensible matter; and this
belongs to mathematics. And there is a third
through the same operation which is the
abstraction of a universal from a particular; and
this belongs to physics and to all the sciences in
general, because science disregards accidental
features and treats of necessary matters. And
14In Metaphysicorum Bk. 7 lec. 10, no. 1496.
15Except by the power of God, as in the Eucharistic species.
Carl: Metaphysics 14
in errorem, ut ponerent mathematica et universalia
a sensibilibus separata, ut Pythagorici et Platonici.
because certain men (for example, the
Pythagoreans and the Platonists) did not
understand the difference between the last two
kinds of distinction and the first, they fell into
error, asserting that the objects of mathematics and
universals exist separate from sensible things.
Here St. Thomas draws his conclusion, associating the two kinds of abstraction with
mathematics and physics and separation with metaphysics, which is also called the divine science.
The objects studied by metaphysics are not abstracted in the strict sense, but are distinguished
through the judgment of separation, in which one negatively judges that being (substance, act,
potency etc.) need not be quantified or material.
The prerequisites for separation
By a careful reading of In DT 5.3, we have established that the objects studied by
metaphysics are grasped by the mind not through abstraction but through a special form of
judgment called separation. In this famous text, however, St. Thomas leaves untreated the question
of how one comes to make the judgment of separation. Among Thomists in the 20th century, the
question of the prerequisites necessary for making the judgment of separation was a source of
significant disagreement. We will sketch here two rival positions.
(1) The River Forest Thomists hold that in order to make the judgment of separation and
begin metaphysics, one must first demonstrate by philosophical argument that positively
immaterial being exists. This can be accomplished by establishing the existence of an immaterial
first cause of motion (as Aristotle establishes in the Physics) or perhaps by proof of the
immateriality of the human soul (as Aristotle takes up in the De Anima). In general, therefore, the
River Forest position is that the study of natural philosophy is not only pedagogically preparatory
for metaphysics, but that it is in fact strictly necessary: on this view, one cannot reasonably study
metaphysics until one knows that positively immaterial being exists, by virtue of previous
philosophical study.
(2) The view favored by authors such as Gilson, Klubertanz, Owens, and Wippel is instead
that one can be in a position to make the judgment of separation without having demonstrated the
existence of the positively immaterial. For example, Msgr. Wippel contends that one already makes
the judgment of separation when one recognizes that a given physical being can be examined
insofar as it is living, or insofar as it is mobile, or insofar as it is material, or simply insofar as it is
a being. That is, what the judgment of separation entails is just that a given being—something that
exists—can be examined just insofar as it is a being, rather than insofar as it is a particular kind of
being. On Msgr. Wippel’s view, St. Thomas’s point in In DT 5.3 is just that the kind of distinction
involved in taking up this perspective—seeing a being qua being—belongs to the order of
separation rather than to the order of abstraction.
It is not my intention to attempt at this point to settle this dispute between River Forest
Thomism and the position generally favored among those, for other reasons, often called
“existential” Thomists, although on this question my opinion tends to favor the latter view. I agree
with Msgr. Wippel that a demonstration in natural philosophy can provide the basis upon which
Carl: Metaphysics 15
one makes the judgment of separation.16 The question is whether or not such a demonstration is the
only way to ground the judgment of separation. However one settles this question about the
prerequisites necessary for the act of separation, it can be held that what this judgment establishes
is that being can be examined simply insofar as it is being. This is what St. Thomas says is the
subject matter of metaphysics.
This being said, in my view, it is possible to begin the project of metaphysics without
having demonstrated the existence of positively immaterial being. That is, one can do just what
Msgr. Wippel claims, which is to consider a being simply insofar as it is a being, even if one has
never demonstrated the existence of the positively immaterial. If one insists that what St. Thomas
calls the judgment of separation can only be justified by a demonstration of the existence of the
positively immaterial, then in my view one could also reasonably conclude that the judgment of
separation is not what establishes the subject of metaphysics; rather, it is a judgment that belongs
to the order of metaphysics.
2.3. Being as Being as the Subject of Metaphysics
The meaning of being as being
As stated above, the subject of metaphysics is being as being or being in general (ens
commune). In his Metaphysics, Aristotle distinguishes the various ways in which being can be
understood in order to clarify the notion of being as being. In Metaphysics 5.7, Aristotle first
distinguishes between accidental being and essential being; he then subdivides essential being into
being in the categories, being as true, and being as actual and potential. I will present these
distinctions as St. Thomas characterizes them in his Commentary on the Metaphysics.
(1) By accidental being (ens per accidens), Aristotle does not mean the being of an
accident, for example the quality white or the relation paternity. Rather, accidental being is that to
which one refers when one predicates something accidentally. For example, that a man is white is
accidental, because it does not belong to the essence of man to be white. The “being” that is
accidental here is what is signified by the underlined is. Aristotle holds that the causes of accidental
being are themselves accidental, such that there cannot be science about this kind of being, since
science is knowledge about the necessary through essential causes.
Essential being (ens per se) is then divided as follows:
(2) Being in the ten categories (or predicaments): St. Thomas calls this being outside the
mind (ens extra animam) and complete being (ens perfectum). Substances and the nine kinds of
accidents are all instances of ens per se, and indeed this is the most important division of essential
being. We will say more about being in the categories in a moment.
(3) Being as true: this is the being of a proposition as composed by the mind. For example,
if I form the judgment that “the apple is red,” this proposition insofar as it is a product of the mind
has being in the mind. St. Thomas explains that it is also the only way in which such things as
privations and negations have being. For example, one can judge that “the dog is blind,” but
blindness is not a real accident of the dog; blindness is rather just the privation of the exercise of
the power of sight in the dog, which is a being that should normally be able to exercise this power.
For this reason being as true is also often referred to as being in the mind.
Being in the categories is then divided as follows:
(4) Being as actual and potential: being in the categories can itself be subdivided in this
16See Wippel 61-62.
Carl: Metaphysics 16
way, into the actual and the potential. For example, a seed is potentially a tree (a substance), and
pale skin is potentially tan (a quality). It is important to note that potential being is an instance of
ens per se extra animam, essential being outside the mind. That is, potential being is not just an
instance of being in the mind, the way that a privation is a being in the mind.17
Of the above divisions of being, Aristotle excludes both accidental being and being as true
from consideration as the subject-matter of metaphysics: these are not being as being or ens
commune as it is studied by metaphysics. This leaves being in the categories, which is further
subdivided into actual and potential being, as the subject-matter of metaphysics. By ens commune
therefore we mean being in the categories, both actual and potential.
God and the subject of metaphysics
In addition to the assertion that metaphysics studies being as being, Aristotle also considers
the possibility that metaphysics studies the highest or best instances of being—these are, for
Aristotle, the separate substances. Aristotle’s attempt at a solution to this question is still a matter of
considerable controversy in scholarly discussions today; what concerns us here is how St. Thomas
answers this question. How is the subject of metaphysics related to the highest being, that is, God?
We can profitably consider St. Thomas’s position on this question in relation to the answers given
previously by the Muslim philosophers Avicenna and Averroes.
Avicenna contends that God (the highest separate substance) is not the subject of
metaphysics, but rather being as being is this science’s subject.18 For Avicenna, metaphysics proves
the existence of God, identifying Him as the first and necessary cause of contingent being. By
contrast, Averroes holds that God’s existence is not established by metaphysics, but rather by
physics (or natural philosophy). According to this latter view, God is the subject of metaphysics as
the first and primary instance of substance: it is because metaphysics studies being as being (which
Averroes takes as primarily meaning substance) that it must study the highest substance in
particular, i.e., God.19
Understanding the positions of Avicenna and Averroes in this way, St. Thomas clearly sides
with the former: St. Thomas contends that the subject-matter of metaphysics is being as being (ens
inquantum est ens) or what he will call being in general (ens commune). Metaphysics primarily
concerns itself with the study of everything that is common to every being, as opposed to the study
of the features that belong only to this or that kind of being. Although God is not the subject of
metaphysics for St. Thomas, nevertheless God is considered by metaphysics—not as its subject,
but as the first cause of being. In other words, metaphysics has as its subject what was termed
above the negative or neutrally immaterial—what is common to all beings—but ultimately
identifies as the cause of its subject what is positively immaterial (God and the separate
substances).
Finally, as we shall explain again and in greater detail later, it is crucially important to note
that God is not a part of the subject of metaphysics: He does not fall under what we will call ens
commune.
17This is a key to Aristotle’s response to the dilemma of Parmenides, who asserted a distinction between
being and non-being that would not allow for the possibility of change. Accepting potential being as real
being serves to defuse this aspect of the Parmenidean dilemma.
18See Wippel 13.
19See Wippel 13-14.
Carl: Metaphysics 17
4. Analogy I: the “Horizontal” Analogy of the Categories
It has become common among contemporary Thomists, following the presentation of
Cornelio Fabro, to distinguish two different levels according to which one can discuss analogy, and
in particular the analogical character of being. We will begin with the notion of analogy that
pertains to ens commune considered in itself; this can be distinguished from the analogy that
obtains between creatures and God.20
4.1. The Notion of Analogy
Univocity and equivocity
To understand the notion of analogy, we must first distinguish between univocity and
equivocity, which are the two basic different ways in which a given term or concept can be related
to two distinct realities. Aristotle draws the distinction between univocal and equivocal terms at the
beginning of his Categories.
A term is used univocally when it is used to name two things, with the same meaning or
definition in each case. For example, when I say that I am a man and that Fr. James is a man, the
term man is used univocally: in each instance that the term is used, it means precisely the same
thing.
By contrast, a term is used equivocally when it is used to name two things, with a different
meaning or definition in each case. For example, bank can refer both to a place where money is
deposited for safe-keeping and the boundary of a river.
Now, according to Aristotle, it cannot be the case that being is a univocal term when it is
taken to refer to substances and to accidents.
Pros hen equivocation
Aristotle distinguishes a third way in which a term can be used, which he calls pros hen
(towards one) equivocation. Strictly speaking, pros hen equivocation is a species of equivocation,
because the same term is used to name two things according to different meanings or definitions.
However, unlike the purely equivocal use of bank or pen to name totally unrelated things, some
terms are used equivocally to name things that are different but closely related to each other.
Aristotle’s most famous example of this kind of equivocation is the term healthy. Consider
the following examples:
(1) The man is healthy.
(2) Exercise is healthy.
(3) Salad is healthy.
(4) The urine is healthy.
The term healthy is used to describe these four things. The use of the term is not univocal. For a
man to be healthy means that his body is generally in good condition, with order and good
operation of his organs. But exercise, salad, and urine do not even have bodily organs: for each of
these things to be healthy cannot be the same thing as for a man to be healthy. Rather, exercise and
salad are called healthy insofar as they are causes of health in a man; and urine is called healthy
insofar as it is a sign of health in a man. This is pros hen equivocation because the meaning of each
of the secondary analogates includes, in its definition, the primary analogate: for example, salad is
20It should be noted that most of the controversy concerning the interpretation of St. Thomas’s thought about
analogy concerns this latter analogy between creatures and God.
Carl: Metaphysics 18
healthy in that it causes the health of a man.
Analogy
Although it is not possible for us to consider at this time the historical background for St.
Thomas’ notion of analogia, we can note that the Thomistic doctrine of analogy has as its most
important precursor the Aristotelian doctrine of pros hen equivocation, but as this was treated and
developed by later Greek and Arabic commentators on Aristotle. Aristotle himself does discuss the
notion of analogia, but for him this term means what it typically means in arithmetic or geometry.
How it is, historically, that pros hen equivocation and analogia came to be intertwined notions is
beyond our present concern. It should only be noted that this historical background helps to explain
some of the developments in St. Thomas’s personal doctrine concerning analogy. However, we will
concern ourselves here only with his mature doctrine.
Just as pros hen equivocation is compared to univocation and equivocation by Aristotle, so
St. Thomas compares analogical predication to both univocal and equivocal predication. In his
early De principiis naturae, c. 6, St. Thomas characterizes these three modes of predication as
follows:
Ad huius intelligentiam sciendum est quod
tripliciter aliquid predicatur de pluribus: univoce,
equivoce et analogice. Univoce predicatur quod
predicatur secundum idem nomen et secundum
rationem eandem, id est diffinitionem, sicut animal
predicatur de homine et de asino: utrumque enim
dicitur animal, et utrumque est substantia animata
sensibilis, quod est diffinitio animalis. Equivoce
predicatur quod predicatur de aliquibus secundum
idem nomen et secundum diversam rationem, sicut
canis dicitur de latrabili et de celesti, que
conveniunt solum in nomine et non in diffinitione
sive significatione; id enim quod significatur per
nomen est diffinitio, sicut dicitur in IV
Metaphysice. Analogice dicitur predicari quod
predicatur de pluribus quorum rationes diverse
sunt, sed attribuuntur uni alicui eidem, sicut sanum
dicitur de corpore animalis et de urina et de
potione, sed non ex toto idem significat in
omnibus: dicitur enim de urina ut de signo
sanitatis, de corpore ut de subiecto, de potione ut
de causa. Sed tamen omnes iste rationes
attribuuntur uni fini, scilicet sanitati.
To understand this it must be known that
something is predicated of several things in three
ways: univocally, equivocally, and analogically.
That is predicated univocally which is predicated
according to the same name and according to the
same intelligible content, which is a definition. In
this way animal is predicated of man and of
donkey: for each is called animal, and each is an
animate sensible substance, which is the definition
of animal. That is predicated equivocally which is
predicated of several things according to the same
name and according to diverse intelligible content.
In this way dog is said of what barks and of a
heaven[ly body], which agree only in name and not
in definition or signification; for that which is
signified through a name is the definition, as is said
in Metaphysics IV. That is said to be predicated
analogically which is predicated of several things
whose intelligible contents are diverse, but are
related to one and the same thing. In this way
healthy is said of the body of an animal and of
urine and of medicine, but it does not signify
entirely the same thing in all of them: for it is said
Carl: Metaphysics 19
of urine as of the sign of health, of the body as of
[its] subject, [and] of medicine as of [its] cause.
Nevertheless all these intelligible contents are
related to one end, namely health.
Whenever something is predicated analogically, it is predicated primarily (per prius) of
one thing and secondarily (per posterius) of other things. The key to understanding St. Thomas’s
notion of analogy is that the secondary analogates are related to the primary analogate according to
some mode of causality: it is causality that provides the connection among the analogates.21 This
causality can be final causality (as it is in the example of health, where the secondary analogates
are ordered to health as an end); it can be efficient causality (as we shall see later in our treatment
of the analogy between God and created being); and it can be material or subject causality.
In commenting on Metaphysics 4.1, St. Thomas offers an important point of development:
Sed sciendum quod aliquid praedicatur de diversis
multipliciter: quandoque quidem secundum
rationem omnino eamdem, et tunc dicitur de eis
univoce praedicari, sicut animal de equo et bove.
Quandoque vero secundum rationes omnino
diversas; et tunc dicitur de eis aequivoce
praedicari, sicut canis de sidere et animali.
Quandoque vero secundum rationes quae partim
sunt diversae et partim non diversae: diversae
quidem secundum quod diversas habitudines
important, unae autem secundum quod ad unum
aliquid et idem istae diversae habitudines
referuntur; et illud dicitur “analogice praedicari,”
idest proportionaliter, prout unumquodque
secundum suam habitudinem ad illud unum
refertur.
Item sciendum quod illud unum ad quod diversae
habitudines referuntur in analogicis, est unum
numero, et non solum unum ratione, sicut est unum
illud quod per nomen univocum designatur.
But it must be known that something is predicated
of diverse [things] in several ways: sometimes
according to entirely the same intelligible content,
and then it is said to be predicated of them
univocally, as animal [is predicated] of horse and
ox. But sometimes according to intelligible
contents in every way diverse: and then it is said to
be predicated of them equivocally, as dog of a star
and of an animal. But sometimes according to
intelligible contents which are partly diverse and
partly not diverse: diverse insofar as they imply
diverse relations, but one insofar as these diverse
relations are referred to something one and the
same; and that is said “to be predicated
analogically,” that is, proportionally, as each of
them according to its own relation is referred to
that one [thing].
Furthermore it must be known that that one, to
which the diverse relations are referred among the
analogates, is one in number, and not only one in
intelligible content, as is the one which is
designated by a univocal name.
21See Wippel 77; Montagnes 26.
Carl: Metaphysics 20
In this text, St. Thomas emphasizes that the primary referent of analogical predication is
always something that is one not merely in ratio (that is, notion or intelligible content) but is also
numerically one: that is, the primary referent of analogical predication is one thing. For example,
in the case of healthy, it is the health (understand as a singular thing, a quality) of the animal that is
the primary referent in relation to which all of the secondary analogates are called healthy.
4.2. The analogy of being on the predicamental level
Although application of the notion of analogy is not restricted to being, nevertheless the
analogy of being is its most famous and most important application in the thought of St. Thomas.
The analogy of being can be formulated on two distinct levels: (1) on the “horizontal” or
predicamental level, according to which being is said analogically of accidents and of substances;
and (2) on the “vertical” or transcendental level, according to which being is said analogically of
God and creatures.22 We will treat the second level of the analogy of being later in our course; for
now, we are concerned with the analogy of being on the predicamental level.
In brief, the theory of Aristotle is that being is a pros hen equivocal term in which the
secondary analogates are the beings in the categories of accidents and the primary analogate is
being in the category of substance.23 St. Thomas holds the same view, but he articulates this claim
in terms of analogy. We will now consider, at length, St. Thomas’s commentary on Metaphysics
4.1.
Dicit ergo primo, quod ens sive quod est, dicitur
multipliciter. . . .
Et ideo dicit quod ens etsi dicatur multipliciter, non
tamen dicitur aequivoce, sed per respectum ad
unum; non quidem ad unum quod sit solum ratione
unum, sed quod est unum sicut una quaedam
natura. . . .
Sed tamen omne ens dicitur per respectum ad
unum primum. Sed hoc primum non est finis vel
efficiens sicut in praemissis exemplis, sed
subiectum. Alia enim dicuntur entia vel esse, quia
per se habent esse sicut substantiae, quae
principaliter et prius entia dicuntur. . . .
Sciendum tamen quod praedicti modi essendi ad
Therefore he says first that being (ens) or what is is
said in many ways. . . .
And therefore he says that being (ens) even if it is
said in many ways, is nevertheless not said
equivocally, but with respect to one; indeed not
[with respect] to a one that is one only in
intelligible content, but which is one as a certain
single nature. . . .
Nevertheless every being (ens) is called [being]
with respect to one first [thing]. But this first
[thing] is not an end or an efficient [cause] as in the
previous examples, but is a subject. For some
things are called beings (entia) or esse, because
they have esse in themelves, such as substances,
which are principally and primarily called beings
(entia).
Nevertheless it must be known that the
22See Wippel 73-74 for this language.
23See Metaphysics 4.1.
Carl: Metaphysics 21
quatuor possunt reduci. Nam unum eorum quod est
debilissimum, est tantum in ratione, scilicet
negatio et privatio, quam dicimus in ratione esse,
quia ratio de eis negociatur quasi de quibusdam
entibus, dum de eis affirmat vel negat aliquid.
Secundum quid autem different negatio et privatio,
infra dicetur.
Aliud autem huic proximum in debilitate est,
secundum quod generatio et corruptio et motus
entia dicuntur. Habent enim aliquid admixtum de
privatione et negatione. Nam motus est actus
imperfectus, ut dicitur tertio Physicorum.
Tertium autem dicitur quod nihil habet de non ente
admixtum, habet tamen esse debile, quia non per
se, sed in alio, sicut sunt qualitates, quantitates et
substantiae proprietates.
Quartum autem genus est quod est perfectissimum,
quod scilicet habet esse in natura absque
admixtione privationis, et habet esse firmum et
solidum, quasi per se existens, sicut sunt
substantiae. Et ad hoc sicut ad primum et
principale omnia alia referuntur. Nam qualitates et
quantitates dicuntur esse, inquantum insunt
substantiae; motus et generationes, inquantum
tendunt ad substantiam vel ad aliquid
praedictorum; privationes autem et negationes,
inquantum removent aliquid trium praedictorum.
aforementioned modes of being can be reduced to
four. For one of these which is the weakest [mode
of being], is [being] only according to reason,
namely negation and privation, which we say exist
according to reason, because [our] reason is
concerned with them as if with certain beings when
it affirms or denies something of them. But in what
way negation and privation differ will be discussed
below.
But another [mode of being] is close to [the first
mode of being] in weakness, insofar as generation
and corruption and motion are called beings
(entia). For they have something admixed with
privation and negation. For motion is the act of the
imperfect, as is said in Physics III.
But the third [mode of being] is called that which
has nothing of non-being admixed, but has weak
being, because [they have esse] not in themselves,
but in another, such as qualities, quantities, and the
properties of substance.
But the fourth kind is that which is most perfect,
which namely has esse in [its] nature without
admixture of privation, and has stable and
complete esse, existing as it were in itself, as are
substances. And to this as to the first and principal
all the others are referred. For qualities and
quantities are said to exist insofar as exist in
substances; motion and generation, insofar as they
tend to substance or to something of the [other]
mentioned [modes of being]; but privations and
negations insofar as they remove something from
the [other] three mentioned [modes of being].
Carl: Metaphysics 22
St. Thomas distinguishes here four modes of being:
(1) The being of privations and negations. -being only according to reason
(2) The being of generation, corruption, and motion. -admixed with non-being
(3) The being of accidents. -being in another
(4) The being of substance. -stable and complete being per se
It is the fourth mode of being distinguished here to which the other three modes are
ultimately referred. Beings of the first mode (privations and negations) are beings of reason, in that
a privation or negation serves to remove or deny being in one of the other three modes (rest is the
negation or privation of motion; blind is the privation of sight; non-substance is the negation of
substance). Beings of the second mode (generation, corruption, and motion) are beings insofar as
they terminate in being in the third or fourth modes—according to Aristotle and St. Thomas,
generation, corruption, and motion occur in the categories of substance, quantity, quality, and
place. Beings of the third mode are related to being of the fourth mode insofar as they exist in
substances as in their subject.
As noted above, for St. Thomas the analogical predication of a term depends upon some
causal relationship that exists among the analogates. In the case of the analogical predication of
being on the predicamental level, the causal relationship between substance and accidents is that
substance is the subject or quasi-material cause of accidents: accidents exist in substances and are
therefore dependent beings. That is, an accident is a being (a habens esse) because it inheres in a
substance, which is being in the primary sense. For this reason, being (ens) is predicated primarily
(per prius) of substance and secondarily (per posterius) of accidents, and the predication of being
as regards accidents is by relation to the category of substance.
Being is not a genus24
Because being is not a univocal term, it is not the case that being is a genus. Every generic
and specific universal term is predicated univocally of the many individuals that fall under these
universals. If being is not a univocal term, then it cannot be a generic or specific universal. Thus,
being is not a genus.25
This conclusion can also be confirmed, as Aristotle argues, by noting that every genus is
divided by differences that are taken from outside the genus.26 Therefore, if being were a genus, it
would have to be divided by non-being. But a difference is always some positive characteristic,
and therefore non-being cannot divide being as if it were a univocal genus.
Therefore, instead of saying that the ten categories are the ten species of being taken as a
genus, St. Thomas prefers to say that the ten categories are ten modes of being. St. Thomas takes it
that when something is divided into various modes, it is not divided in the same way as a genus is
divided into species. The ten categories are therefore better thought of as the ten different ways in
which things can exist extra animam, rather than as ten kinds of being.
Is being ever predicated univocally?27
Given that being is not a genus divided into the ten categories, the next question to arise is
whether being can ever be said univocally of two things that are the same in some way. For
24See Wippel 87-90.
25There are texts in which St. Thomas speaks of being as a genus—in these texts, we must conclude that the
term genus is itself being used in an analogical sense.
26See Metaphysics 998b21-27.
27See Wippel 90-93.
Carl: Metaphysics 23
example, are two members of the same genus or of the same species called beings univocally?
St. Thomas’s answer to this question can be articulated at three different levels:
(1) St. Thomas holds that different levels or grades of substance are not beings univocally;
by this he means that incorporeal substances (i.e., the angels) do not share being univocally with
corporeal substances (e.g., you and me). His reasoning for this claim is beyond what we can fully
explain at the present, but it involves his claims about the composition of esse and essence in every
created substance.
(2) Among substances of the same level or grade but of distinct species (e.g., a dog and a
man), St. Thomas holds that once again being is not predicated univocally. Again the reason for
this view is beyond our present attention.
(3) It can also be asked whether or not being is predicated univocally of two substances of
the same species (e.g., of two men). As Msgr. Wippel notes, Thomists have differed historically on
this question: John of St. Thomas rejects analogical predication of being in this case, but Msgr.
Wippel offers reasons for holding that even this predication of being will be analogical.28 If his
view on this point is correct, then it will never be the case that being is predicated univocally of
any two distinct things.
Concluding remarks concerning predicamental analogy
It should be noted that what we have called the predicamental analogy of being—the
analogy according to which being is said of both accidents and of substance—is not the only type
of analogy of being in the thought of St. Thomas, and indeed it is far less commented upon than the
other kind of analogy of being, that which obtains between created being and uncreated being. The
Aristotelian theory according to which being is said primarily of substance and secondarily of
accidents is accepted by St. Thomas in a straightforward way, with relatively little need for
extensive clarification by scholarship. What we will later call the transcendental analogy between
God and creatures requires much more careful consideration.
28See Wippel 93. The reason Msgr. Wippel offers is that St. Thomas asserts that esse understood as the act of
existing (actus essendi) is present in only one thing and is only analogically common to two things. But
since being (ens) is understood as what has being (quod habens esse), it follows that ens too can only be
analogically common even to two members of the same species.
Carl: Metaphysics 24
5. Participation
A theme in the thought of St. Thomas that has received much greater attention since the
mid-20th century is that of participation. That the notion of participation deserves sustained
attention should be clear simply from the frequency with which St. Thomas employs the language
of participation in his writings.29 Even if one should conclude that participation is not a notion that
is fundamental to St. Thomas’s metaphysical thought, still one must contend with what St. Thomas
means by the language of participation.
As we shall see, St. Thomas frequently uses the language of participation to express his
doctrine of the real composition of esse and essence in (created) beings. We have not yet addressed
any of St. Thomas’s reasoning in support of this position; for now, our purpose is only to
understand the meaning of this language of participation. Following the presentation of Msgr.
Wippel, we will begin by considering what St. Thomas means by participation in general, with a
quick consideration of St. Thomas’s attitude towards the Platonic theory of participation.
5.1. St. Thomas’s Attitude Towards Plato on Participation
The historical background for the notion of participation is primarily Platonic: one finds in
the dialogues of Plato the famous claim that individual sensible realities participate in the eternal,
immaterial Forms. In this way, Socrates is supposed to be a man by his participation in the separate
Form, man-itself. Concerning this theory, in addition to his more substantive critiques, Aristotle is
famously dismissive of the very language of participation (Metaphysics 1.6):
In his Commentary on this text, St. Thomas shifts the blame for not considering the
meaning of participation exclusively onto the Pythagoreans (In Meta. 1.10):
Hoc autem nomen participationis Plato accepit a
Pythagora. Sed tamen transmutavit ipsum.
Pythagorici enim dicebant numeros esse causas
rerum sicut Platonici ideas, et dicebant quod
huiusmodi existentia sensibilia erant quasi
quaedam imitationes numerorum. Inquantum enim
numeri qui de se positionem non habent,
accipiebant positionem, corpora causabant. Sed
quia Plato ideas posuit immutabiles ad hoc quod de
Now Plato took this name of participation from
Pythagoras. But he altered it. For the Pythagoreans
said that numbers are the causes of things, just as
the Platonists [say that] the ideas [are]; and they
said that sensible existents of this kind are certain
imitations of numbers. For insofar as numbers,
which of themselves do not have position, received
position, they caused bodies. But because Plato
held the ideas [to be] immutable in order that there
29Quick searches on the Index Thomisticus reveal that St. Thomas’s use of the language of participation is in
fact more common than his use of the (explicit) language of analogy.
For according to [Plato], it is impossible that there should be a common definition of any one of these
sensible things which are always changing. Such entities, then, he called Ideas or Forms (species); and
he said that all sensible things exist because of them and in conformity with them; for there are many
individuals of the same name because of participation in these Forms. With regard to participation, he
[merely] changed the name; for while the Pythagoreans say that things exist by imitation of numbers,
Plato says that they exist by participation, changing the name. Yet what this participation or imitation of
Forms is they commonly neglected to investigate.
Carl: Metaphysics 25
eis possent esse scientiae et definitiones, non
conveniebat et in ideis uti nomine imitationis. Sed
loco eius usus est nomine participationis. Sed
tamen est sciendum, quod Pythagorici, licet
ponerent participationem, aut imitationem, non
tamen perscrutati sunt qualiter species communis
participetur ab individuis sensibilibus, sive ab eis
imitetur, quod Platonici tradiderunt.
could be science and definitions about them, he did
not agree [with the Pythagoreans] in using the
name of imitation. But in its place he used the
name of participation. But it must be known that
the Pythagoreans, although they posited
participation or imitation, nevertheless they did not
scrutinize how a common species is participated or
imitated by sensible individuals; [but] the
Platonists did treat this.
Whereas Aristotle seems to blame Plato along with the Pythagoreans for failing to
carefully consider the meaning of participation, St. Thomas preserves the Platonists from this
criticism: even if, as we shall see, he sides with Aristotle rather than the Platonists concerning the
reality of separate Forms, and he expresses the Aristotelian position concerning the relationships
between particulars and universals in the language of participation.
5.2. The Meaning of Participation in General
St. Thomas’s most careful presentation of the meaning of participation is found in his
Commentary on the De Hebdomadibus of Boethius, lec. 2.30 He begins with an etymological
explanation of the meaning of participare:
Est autem participare quasi partem capere. Et ideo
quando aliquid particulariter recipit id quod ad
alterum pertinet universaliter, dicitur participare
illud, sicut homo dicitur participare animal quia
non habet rationem animalis secundum totam
communitatem; et eadem ratione Sortes participat
hominem.
But to participate is, as it were, to take a part. And
therefore when something receives in a particular
way that which belongs to another in a universal
way, it is said to participate that, as man is said to
participate animal since [man] does not possess the
intelligible content of animal according to [its]
entire community; and in the same way Socrates
participates man.
To participate is “to take a part” of something, to receive and possess in a particular or
partial way what belongs to something else in a universal or total way. Consequently, a species
is said to participate (in) its genus, and an individual is said to participate (in) its species (and its
various genera). When it is said that a species participates its genus and that an individual
participates a universal, in both cases we can take this to mean that the former does not exhaust the
intelligible content of the latter. For example, man is but one particular kind of animal.
Consequently, there are things belonging to animal taken as a universal whole (namely, the things
belonging to non-human animals according to their differentiating characteristics) that do not
30It is worth noting that Boethius, in general, was committed to the harmony between the thought of Plato
and the thought of Aristotle. He expresses this view early in the Consolation of Philosophy, and he
characterizes the defense of this view as a central aim of his own philosophical exertions.
Carl: Metaphysics 26
belong to man. Similarly, Socrates does not exhaust the intelligible content of humanity; by being
this man, with this flesh and these bones, Socrates is one limited instantiation of the universal man.
Now, because the distinction between man and animal and the distinction between
Socrates and man are logical or intentional distinctions, this participation of a species in its genus
or of a particular in a universal can be rightly characterized as a logical or intentional participation
rather than as an instance of real participation.31
To summarize, to receive in a particular way what belongs to something else in a universal
way is the general meaning of the term participation for St. Thomas, and it is exemplified by the
participation of a species in its genus and of a particular in the universal. St. Thomas then extends
the meaning of participation to a second set of cases, which involve composition:
Similiter etiam subiectum participat accidens et
materia formam, quia forma substantialis vel
accidentalis, que de sui ratione communis est,
determinatur ad hoc vel illud subiectum.
And similarly, a subject participates [its] accident
and matter [participates its] form, since a
substantial or accidental form, which is common
from its intelligible content, is determined to this
or that subject.
A subject—i.e., a substance—is said to participate (in) its accident, and matter participates
(in) form. These are both instances of composition that we will treat in greater detail later in the
course, in our consideration of the various ways in which ens commune is composite. As we will
see in these later treatments, St. Thomas will analyze both subject-accident composition and
matter-form composition as the composition of a principle of potency with an actualizing principle.
Again, what is fundamentally at issue in calling these cases participation is that the receiving
subjects—substance and matter—do not share in the character of the forms that they receive in an
exhaustive way. Because these examples of participation concern instances of real composition,
one can refer to this as real (or ontological) participation rather than logical participation—
although the claim that these are instances of real composition is something we will defend later in
the course.
Now, one might ask what the relationship is between the participation of an individual in a
universal and the participation of matter in form, since there seem to be examples that are closely
related: Socrates participates in man, and the matter of Socrates participates in the form or nature
of humanity. In the Commentary on the Metaphysics 1.10, immediately prior to the comments
about Pythagoras and Plato that we cited earlier, St. Thomas makes the following remarks:
Individuum autem est homo per participationem,
inquantum natura speciei in hac materia designata
participatur. Quod enim totaliter est aliquid, non
participat illud, sed est per essentiam idem illi.
Quod vero non totaliter est aliquid habens aliquid
aliud adiunctum, proprie participare dicitur. Sicut
But the individual is man by participation, insofar
as the nature of the species is participated in this
designated matter. For that which is something in a
total way, does not participate that [something], but
is that same thing by essence. But what is
something not totally, [rather] having something
31See Wippel 97 and his reference to Fabro and Geiger in n. 9 for this point.
Carl: Metaphysics 27
si calor esset calor per se existens, non diceretur
participare calorem, quia nihil esset in eo nisi
calor. Ignis vero quia est aliquid aliud quam calor,
dicitur participare calorem.
else joined [to it], is properly said to participate.
For example, if heat were a heat existing per se, it
would not be said to participate heat, since there
would be nothing in it but heat. But fire, since it is
something other than heat, is said to participate
heat.
The context for these remarks is that St. Thomas is presenting, so far as possible, the
Platonic account of participation in separate Forms in a positive light. We will return to this text in
its complete context later when we discuss the principle of individuation (the designated matter
that St. Thomas refers to in this text). For now, I only want to highlight that St. Thomas grounds
the participation of the individual in the universal in the participation of matter in form: the former
logical or intentional participation is grounded in a real participation and a real composition. For
this reason, here St. Thomas characterizes participation in the proper sense as the characteristic of
something that is joined to (i.e., composed with) something else.
We should also highlight as important the contrasting of what is per participationem with
what is per essentiam: one will find that St. Thomas frequently makes appeal to this distinction in
his writings.
Returning to our consideration of the Commentary on the De hebdomadibus, lec. 2, St.
Thomas then adds a third use of the term participation:
Et similiter etiam effectus dicitur participare suam
causam, et precipue quando non adequat virtutem
suae causae, puta si dicamus quod aer participat
lucem solis quia non recipit eam in claritate qua est
in sole.
And similarly too an effect is said to participate its
cause, and especially when [the effect] is not equal
to the power of its cause, as for example if we say
that air participates the light of the sun, since it
does not receive [light] with the brilliance it has in
the sun.
When something receives from its efficient cause a perfection that belongs to that cause,
but it receives that perfection in a limited or determinate way relative to the more complete
existence of that perfection in the cause, then that thing can be said to participate (in) the perfection
of the cause. St. Thomas does not offer any elaboration on this third case of participation, but it is a
usage that we will want to recall later.
To summarize, these are the cases or kinds of participation described by St. Thomas:
1) the participation of a species in a genus or of an individual in a species
2) the participation of substance in accident and of matter in form
3) the participation of an effect in its cause
5.3. Participation and Being
Conveniently enough, in the very text that we have considered as a source for St. Thomas’s
understanding of the notion of participation, St. Thomas is concerned with commenting on remarks
made by Boethius about participation and being. We can address ourselves to two questions in
Carl: Metaphysics 28
order: (1) does being participate in anything? (2) In what sense can beings (entia) be said to
participate in being (esse)? We will not at this time address either of these questions in full detail.
As mentioned before, some of the following comments will presume St. Thomas’s thesis that there
is real composition of essence and esse in created beings—this thesis will be considered as our
next major topic in this course.
To begin, it will be helpful to consider the text of Boethius about which St. Thomas is
commenting. The numbers here indicate the numbers of the seven axioms presented by Boethius:32
Does being participate in anything?
As we have seen before, one can understand being as that-which-is (id quod est, ens) or as
the existence or being (esse) that is the act of an essence. We find this very distinction articulated
in the first axiom of Boethius: esse and id quod est are diverse. St. Thomas comments on this
distinction as follows:
Dicit ergo primo quod diversum est esse et id quod
est, quae quidem diversitas non est hic referenda
ad res de quibus adhuc non loquitur, sed ad ipsas
rationes seu intentiones. Aliud autem significamus
per hoc quod dicimus esse et aliud per id quod
He says first therefore that esse and id quod est are
diverse, which diversity is not here referred to the
realities, of which he has not yet spoken, but to the
notions or intentions themselves. But we signify
one thing when we say esse and another when we
32The translation here is a translation of the text of Boethius as found in the Leonine edition of St. Thomas’s
Commentary. The translation is that of Janice Schultz and Edward Synan in their An Exposition of the
“On the Hebdomads” of Boethius (Washington, DC: The Catholic University of America Press, 2001),
xxxi & 15.
(1) Being (esse) and that-which-is (id quod est) are diverse. For being itself (ipsum esse) as yet is not.
That-which-is, however, once the form of being has been taken on, is and stands together.
(2) What-is (quod est) can participate in something, but being itself (ipsum esse) in no way participates
in anything. For participation occurs when something already is. Something is, however, when it has
received being (esse).
(3) That-which-is can possess something other than what it itself is. Being itself, however, has nothing
else outside itself as an admixture.
(4) However, to be something, and to be something in this, that [a thing] is, are diverse. For by the
former, accident is signified; by the latter, substance.
(5) Everything that is (omne quod est) participates in that which is being (eo quod est esse) with the
result that it be (ut sit). It participates in something else with the result that it be something. And
through this, that-which-is participates in that which is being with the result that it be. It is, however,
with the result that it can participate in anything else whatever.
(6) In every composite, being (esse) is other than the item itself. Every simple item possesses its being
(esse) and that-which-is (id quod est) as one.
(7) All diversity is discordant, whereas similitude must be sought. And what seeks something else is
shown to be itself by nature such as that which it seeks.
What we have set down as preliminaries, therefore, suffice. Each one will be applied in argumentation
by the prudent interpreter of their meaning.
Carl: Metaphysics 29
dicimus id quod est, sicut et aliud significamus
cum dicimus currere et aliud per hoc quod dicitur
currens. Nam currere et esse significatur in
abstracto sicut et albedo; sed quod est, id est ens et
currens, significatur in concreto velut album.
say id quod est, just as we also signify one thing
when we say “to run” and another when we say
“running.” For to run and to be (esse) are signified
in the abstract, like whiteness; but what is, that is, a
being (ens) and [one] running, are signified in the
concrete, like white [thing].
The distinction between esse and id quod est or ens is not initially to be construed as a real
distinction, but instead should be construed as a distinction in notion or intention—i.e., as a logical
distinction. Similarly, one can draw a logical distinction between “one running” and “to run,” or
between “white thing” and “whiteness,” as between the concrete and the abstract. Considered in
this way, therefore, the distinction between ens and esse is just the logical distinction between an
existent in the concrete and existence in the abstract.
Given this distinction between esse and id quod est, the question of whether being
participates in anything can therefore be understood in two ways: (a) Does esse participate in
anything? (b) Does that-which-is participate in anything?
Does esse participate in anything?
In his Commentary, following the preceding elaboration of the distinction between esse
and id quod est, St. Thomas immediately comments on the question of whether esse participates
anything:
Deinde cum dicit: Ipsum enim esse etc., manifestat
praedictam diversitatem tribus modis.
Quorum primus est quia ipsum esse non
significatur sicut subiectum essendi, sicut nec
currere significatur sicut subiectum cursus. Unde
sicut non possumus dicere quod ipsum currere
currat, ita non possumus dicere quod ipsum esse
sit; sed id quod est significatur sicut subiectum
essendi, velut id quod currit significatur sicut
subiectum currendi; et ideo sicut possumus dicere
de eo quod currit sive de currente quod currat in
quantum subicitur cursui et participat ipsum, ita
possumus dicere quod ens sive id quod est sit in
quantum participat actum essendi.
Then when he says: For being itself, etc., he shows
the aforementioned diversity in three ways.
Of these, the first is that being (esse) itself is not
signified as the subject of being, as “to run” is not
signified as the subject of running. Wherefore, just
as we cannot say that “to run” itself runs, so we
cannot say that being (esse) itself is; but that which
is (id quod est) is signified as the subject of being,
just as that which runs is signified as the subject of
running; and therefore just as we can say of that
which runs or of the runner that he runs insofar as
he is the subject of running and participates it, so
we can say that being (ens) or that which is (id
quod est) is insofar as it participates the act of
being (actus essendi).
Given only the logical distinction between ens and esse as the distinction between the
concrete and the abstract, it cannot be said that esse participates ens; rather, ens participates esse
insofar as it is the subject of esse, just as the runner is the subject of and participates running, rather
Carl: Metaphysics 30
than vice versa. St. Thomas proceeds to explain that it is for this reason that Boethius next says
being itself as yet is not (ipsum esse nondum est): ens is, because ens is the subject of esse, but esse
is not the subject of anything, and so it cannot be said that esse is any more than it is said that to
run runs.
After providing the threefold explanation of the notion of participation that we considered
above, St. Thomas proceeds to offer more comments concerning the (im)possibility that esse
should participate in anything:
Praetermisso autem hoc tertio modo participandi,
impossibile est quod secundum duos primos
modos ipsum esse participet aliquid. Non enim
potest participare aliquid per modum quo materia
vel subiectum participat formam vel accidens quia
ut dictum est ipsum esse significatur ut quiddam
abstractum. Similiter autem nec potest aliquid
participare per modum quo particulare participat
universale; sic enim etiam ea quae in abstracto
dicuntur participare aliquid possunt sicut albedo
colorem, sed ipsum esse est communissimum,
unde ipsum quidem participatur in aliis, non autem
participat aliquid aliud.
But this third mode of participating set aside, it is
impossible that being (esse) itself participate
something according to the first two modes. For it
cannot participate something through the mode by
which matter or a subject participates form or
accident, since as was said being (esse) itself is
signified as something abstract. Nor similarly can
it participate something through the mode by
which a particular participates a universal; for in
this way too those things which are said in the
abstract can participate something, as whiteness
participates color, but being (esse) itself is most
common, indeed such that it is participated by
others, but it does not participate something else.
Without commenting at this moment on the third mode of participation, St. Thomas
excludes the first two modes of participation with regard to esse itself as that which participates.
However, in his explanation, he has noted that esse is most common (communissimum), with the
consequence that other things participate in esse, but esse does not participate in anything else.33
Does that-which-is participate in anything?
Thus, it will come as no surprise that St. Thomas defends the view that that-which-is does
participate in something else. First, and most importantly, it can be said that ens participates in
esse. Our purpose for now is to sketch only a general sense in which such a claim may be
articulated: fuller clarity about participation in esse will come only after we have discussed the real
composition of essence and esse in created substances and the existence of God, to Whom St.
Thomas will refer as ipsum esse per se subsistens.34 St. Thomas continues, in the text we have been
studying as follows:
33As we will discover later, this is a way of saying that esse is a transcendental term. St. Thomas often refers
to the transcendentals as the communissima.
34It must suffice for now to note that the qualification per se subsistens serves to distinguish the divine esse
from ipsum esse in the sense of esse commune (the act of [created] being in general). Esse commune is
signified in the abstract, as something that is not per se subsistens.
Carl: Metaphysics 31
Sed id quod est sive ens, quamvis sit
communissimum, tamen concretive dicitur, et ideo
participat ipsum esse, non per modum quo magis
commune participatur a minus communi, sed
participat ipsum esse per modum quo concretum
participat abstractum. Hoc est ergo quod dicit quod
id quod est, scilicet ens, participare aliquo potest;
sed ipsum esse nullo modo participat aliquo; et
hoc probat ex eo quod supra dictum est, quod
scilicet ipsum esse nondum est. Manifestum est
enim quod id quod non est non potest aliquo
participare, unde consequens est quod participatio
conveniat alicui cum iam est; sed ex hoc aliquid
est quod suscipit ipsum esse sicut dictum est. Unde
relinquitur quod id quod est aliquid possit
participare, ipsum autem esse non possit aliquid
participare.
But that-which-is or being (ens), although it is
most common, nevertheless is said concretely, and
therefore it participates being (esse) itself, not
through the mode by which the more common is
participated by the less common, but [that-whichis] participates being (esse) itself through the mode
by which the concrete participates the abstract.
This, therefore, is what he says, that that-which-is,
namely being (ens), can participate in something;
but being (esse) itself in no way participates in
anything; and he proves this from what was said
above, namely that being (esse) itself as yet is not.
For it is manifest that that-which-is-not cannot
participate in anything, whence it follows that
participation belongs to something when it already
is; but something is by this that it receives being
(esse) itself, as was said. Wherefore, it remains that
that-which-is can participate something, but being
(esse) itself cannot participate anything.
It is important to emphasize that the participation of ens in esse as articulated here
presumes only the logical distinction between the concrete and the abstract: ens participates esse
just as a runner participates in “to run,” and a white thing participates in whiteness. As St. Thomas
is careful to point out, the participation of ens in esse is not even a case of participation of the less
common in the more common, because both ens and esse are communissimum, most common.
Nevertheless, as we shall see in consideration of our next major topic (real composition of essence
and esse in created substances), St. Thomas is here paving the way for an argumentation for a real
distinction rather than a merely logical distinction between that-which-is and esse itself.
We will comment more in a moment on the claim that that-which-is (ens) can be said to
participate being (esse). For now, we should note another sense in which ens is said to participate
in something. We have already observed that a substance can be said to participate an accident.
According to the analogical character of ens, which is predicated primarily of substance, the
participation of substance in accident is the participate of ens in something. St. Thomas speaks
about substance-accident participation as the participation of ens in something later in the same
text we have been considering at length, Exp. De heb. lec. 2.
First, it should be noted that just as St. Thomas characterizes the participation of ens in
esse at first according to the participation of the concrete in the abstract, so too does he note that
human participates humanity and that white participates whiteness.
Ex hoc autem quod homo habet humanitatem vel
album albedinem, non prohibetur habere aliquid
But from this that man has humanity or white
whiteness, it is not precluded [that it] have
Carl: Metaphysics 32
aliud quod non pertinet ad rationem horum, nisi
solum quod est oppositum hiis; et ideo homo et
album possunt aliquid aliud habere quam
humanitatem vel albedinem; et haec est ratio quare
albedo et humanitas significantur per modum
partis et non praedicantur de concretis sicut nec
aliqua pars de suo toto. Quia igitur, sicut dictum
est, ipsum esse significatur ut abstractum, id quod
est ut concretum, consequens est verum esse quod
hic dicitur quod id quod est potest aliquid habere
praeter quam quod ipsum est, id est praeter suam
essentiam, sed ipsum esse nihil aliud habet
admixtum praeter suam essentiam.
something other that does not pertain to the
intelligible content of these, except only that which
is opposed to these; and therefore man and white
can have something other besides humanity or
whiteness; and this is the reason why whiteness
and humanity are signified in the manner of a part
and are not predicated of concrete [items], just as a
part [is] not [predicated] of its whole. Since
therefore, as was said, being (esse) itself is
signified as abstract, [and] that-which-is as
concrete, it follows that what is said here is true,
that that-which-is can have something other than
what it itself is, that is, outside its essence, but
being (esse) itself has nothing else admixed outside
its essence.
This possibility of ens receiving something not contained in its own essence is articulated
in two ways by St. Thomas: (1) in terms of the reception of esse, which is not contained in the
content of a thing’s essence; and (2) in terms of the reception of an accident, which is also not
contained in the content of a thing’s essence. To discuss the first kind of reception by ens of
something not contained in its essence will be the next major topic of discussion—the real
composition of essence and esse—to which we will turn shortly. For now, we want to consider the
participation of ens in accident, which St. Thomas considers in the same text:
Si vero sit talis forma quae sit extranea ab essentia
habentis eam, secundum illam formam non dicitur
habens esse simpliciter, sed esse aliquid, sicut
secundum albedinem homo dicitur esse albus. . . .
Dicit quod ad hoc aliquid sit simpliciter subiectum
participat ipsum esse, sed ad hoc quod sit aliquid,
oportet quod participet aliquo alio, sicut homo ad
hoc quod sit albus participat non solum esse
substantiale sed etiam albedinem.
But if the form be such that it is extraneous to the
essence of what possesses it, according to that
form it is not called something having being
(habens esse) without qualification, but [something
having] to-be-something (esse aliquid), as
according to whiteness man is said to be white. . . .
He says that for this that something be a subject
without qualification it participates being (esse)
itself, but for those that it be something, it is
necessary that it participate something else, as
man, for this that he be white, participates not only
substantial being (esse) but also whiteness.
The participation of a substance in accident is thus a kind of participation of ens or id quod
est in something else, because it does not pertain to this or that subject to include in its essence this
Carl: Metaphysics 33
or that accidental characteristic. In this way, then, ens can be said to participate in something.
To summarize, then, ens or that-which-is can be said to participate in two general ways: it
participates in esse, and it participates in accident. With regard to the former, so far we have
articulated only a logical or intentional way in which ens participates esse: we will now turn to the
distinct senses in which the participation of ens in esse can be understood.
In what distinct senses can beings (entia) be said to participate being (esse)?
We have already indicated that ens participates esse as the concrete participates the
abstract, just as white participates whiteness. So, it will be no surprise at this point that St. Thomas
does affirm that beings (entia) participate being (esse). However, by such an expression St.
Thomas typically means more than just the expression of a logical or intentional distinction
between the concrete being and its act of being taken in the abstract (which can be compared to the
concrete runner and his act of running taken in the abstract). We will here comment briefly on a
subject to which Msgr. Wippel devotes considerable attention (pp. 110-24): what does it mean to
say that beings participate esse? Following Msgr. Wippel’s presentation, we can distinguish three
senses in which this claim can be taken. Because the following comments will presuppose both the
real composition of essence and esse in finite realities and the existence of God, Who is ipsum esse
per se subsistens, what we are considering can be said to be usages of the phrase “participation in
esse” that will only be justified by virtue of arguments that will be given later in the course.35
(1) To participate in esse can be understood as to participate in esse commune, which is
esse understood as an analogically common perfection in which all finite or composite realities
share. This esse commune is not to be identified with God; rather, as will be discussed later in the
course, esse commune is caused by God. When we say that esse commune is an analogically
common perfection, we mean to exclude that esse commune be understood as a separate form
distinct from the individuals that participate it. That is, esse commune is not a Platonic Form.
Rather, each concrete ens possesses its own esse or act of existence, and insofar as one considers
esse to be a perfection shared in common, one calls this esse commune.
(2) To participate in esse can be understood as to participate in ipsum esse per se
subsistens, that is, in divine esse. This is not St. Thomas’s preferred mode of expression, but he
does speak in this way on occasion. This can only be understood as the participation of an effect in
its cause: one must exclude any notion that the divine esse itself is somehow communicated or
diversified in created beings. As Msgr. Wippel details, for this reason more often says that finite
beings participate a likeness of the divine esse, by which he means that they participate their own
esse, which is caused by and bears some likeness to the divine esse. Alternatively, St. Thomas will
say that beings participate esse from God. As Msgr. Wippel notes, the participation of beings in
esse commune is therefore ultimately grounded in their participation in divine esse, understood as
the participation of an effect in its cause.
(3) A being can be said to participate in esse insofar as it participates its own act of
existence: this is like the participation in esse commune, but one considers this concrete being’s act
of existence in particular rather than considering esse as a perfection that is analogically common
to many. What does it mean to say that this being participates its own actus essendi? The answer to
this question can only be given by answering a much more difficult question, to which we will
given only limited attention in this course: What is it that accounts for the limited or finite
character of a created reality? The claim that a finite being participates its own actus essendi can be
well understood, if one accepts the claim that it is primarily a thing’s essence rather than its esse
35See Msgr. Wippel’s summary remarks on pp. 120-21.
Carl: Metaphysics 34
that should be taken as the principle according to which it is finite and limited.36
36For Msgr. Wippel’s preliminary remarks on this point of dispute, see pp. 124-31.
Carl: Metaphysics 35
6. Real Composition of Essence and Esse in Finite Beings
Having noted that being in general (ens commune) is a common subject of study according
to analogical rather than univocal unity, we can proceed to a consideration of ens taken in its
primary referent, which is substance. What the predicamental analogy of being allows us to do, in
our consideration of ens commune (the subject of metaphysics), is to justify this initial focus on
substance. Because of the analogy of being, we understand that whatever we say about substance
will have implications for what we will say about accidents.
The central note of St. Thomas’s analysis of finite being, and particularly of substance, is
that finite being is composite, in various ways. We will begin with what is perhaps St. Thomas’s
most famous metaphysical thesis, the real distinction and composition of esse and essence in finite
beings.
6.1. Background: Relation of Concepts to Reality; Real and Logical Distinction
Medieval philosophers and theologians generally recognized a distinction between esse
(existence) and essence in created things, but it was a matter of significant dispute whether this
distinction is a real distinction or merely a logical or conceptual distinction. That is, is this
distinction between esse and essence a real feature of the world even apart from the consideration
of the mind? Or is it a distinction that only exists in the mind, in the way that (for example) the
distinction between dog and animal is a logical distinction that is not really present in a dog?37
To understand the question posed, we should draw two related distinctions. First, St.
Thomas distinguishes between three ways in which a concept of the intellect can be related to
things outside the mind, as follows:38
(1) What is conceived by the intellect can be a similitude (i.e., a likeness) of something
existing outside the mind. For example, one’s concept of man is a likeness of a thing existing
outside the mind, that is, of a man. Such a concept has an immediate foundation in the thing
outside the mind, insofar as the concept of man is a likeness of the essence of man; and this
likeness comes to exist as the product of the act of understanding.39
(2) What is conceived by the intellect is sometimes not a likeness of anything outside the
mind, but is rather something that arises from the activity of understanding. For example, the
concept of a genus is not a similitude of anything existing outside the mind; rather, it is a concept
that arises is consideration of the relationship between the essence animal and the various kinds of
things that possess this essence. The concept of genus has its foundation in things outside the mind;
this is not an immediate foundation, but a remote foundation. (These intentions, such as genus or
species, are typically called second intentions, as distinguished from first intentions, which are
concepts of the first kind distinguished above.)
(3) Finally, what is conceived by the intellect can fail to be a likeness of anything outside
37That is, in reality, a dog is not “composed” of animal and dog. This can be recognized from the fact that the
ratio of dog includes the ratio of animal.
38In Sent. 1.2.1.3.
39It should be noted that the concept taken in this sense is distinct from the intelligible species that is
abstracted from the phantasm. The intelligible species is the formal principle of the act of understanding,
whereas the concept is the terminus or product of the act of understanding. Both the intelligible species
and the concept are likenesses of the thing outside the mind, but one does not possess any awareness of
an intelligible species, while one is aware of one’s concept.
Carl: Metaphysics 36
the mind, such as the concept of a chimera. Such a concept has no foundation except the mind
itself.
Now, one can also draw a related distinction between two kinds of distinction: this is the
distinction between a real distinction and a distinction of reason.
(a) In a real distinction, one distinguishes two items that are distinct in reality even apart
from the consideration of the mind, because the two items are not identical in reality. For example,
a man is really distinct from a dog, even prior to the consideration of the mind. This is obviously a
case of a real distinction, because a dog and a man possess independent existence as substances.
(b) In a distinction of reason (or a logical or conceptual distinction), one draws a
distinction between things that are not absolutely distinct apart from the consideration of the mind.
That is, one considers a single thing according to distinct concepts. An obvious example of a
distinction of reason is the distinction between the morning star and the evening star (which are
identical in reality: they are both the planet Venus). St. Thomas will also say (as we will see later in
our course) that the divine attributes are not really distinct but are only distinct according to reason.
Indeed, the texts where St. Thomas brings up the difference between real and logical distinction are
almost exclusively concerned with theological questions: he affirms on the one hand that the
distinction between the divine Persons is a real distinction40, whereas the distinction between the
divine attributes is a distinction of reason.41
A number of later authors (such as Ockham) will understand real distinction exclusively as
the distinction between one thing (res) and another thing (res) which exist or can exist
independently from one another, such as a man and a dog or a man and his arm. If this is what is
meant by a real distinction, then a real distinction always implies the possible separate existence of
the items distinguished. This is not, however, how St. Thomas understands a real distinction: it is
not a requirement for a real distinction that the items distinguished be capable of existing
independently from one another.
For example, as we will explain below, for St. Thomas the distinction between substantial
form and prime matter is a real distinction, because these are two principles that enter into real
composition in a corporeal substance: but neither the matter nor the form is capable of existing
independently of the composite. (The only exception to this is the human soul, which is a
substantial form that survives the corruption of the human substance.) Substantial form and matter
are really distinct, according to St. Thomas’s understanding of real distinction, despite the fact that
neither the substantial form (except for the human soul) nor the prime matter is capable of
independent existence as a thing.
Much of the controversy about whether the distinction between essence and esse is a real
distinction or only a distinction of reason hinges on what one understands as the implications of a
real distinction with regard to the possible independent existence of the items distinguished.
Therefore, when we argue that essence and esse are really composite and really distinct in created
things, we do not mean to imply (absurdly) that an essence could exist apart from its esse.
6.2. Argument for Real Composition of Essence and Esse
One can distinguish in St. Thomas’s writings a variety of ways of arguing for the claim that
40See In Sent. 1.2.1.5.
41See In Sent. 1.2.1.3.
Carl: Metaphysics 37
esse and essence are really distinct and composite in finite beings. With our limited time, we will
begin by considering St. Thomas’s comments concerning real composition in the context of the
long text to which we have given significant attention under the heading of participation, Exp. De
heb., lec. 2. In this place, St. Thomas writes:
Deinde cum dicit: Omni composito etc., ponit
conceptiones de composito et simplici, quae
pertinent ad rationem unius, et est considerandum
quod ea quae supra dicta sunt de diversitate ipsius
esse et eius quod est, est secundum ipsas
intentiones. Hic ostendit quomodo applicetur ad
res; et primo ostendit hoc in compositis, secundo
in simplicibus, ibi: Omne simplex etc.
Est ergo primo considerandum quod sicut esse et
quod est differunt secundum intentiones, ita in
compositis differunt realiter. Quod quidem
manifestum est ex praemissis. Dictum est enim
supra quod ipsum esse neque participat aliquid ut
eius ratio constituatur ex multis, neque habet
aliquid extrinsecum admixtum ut sit in eo
compositio accidentalis; et ideo ipsum esse non est
compositum; res ergo composita non est suum
esse; et ideo dicit quod in omni composito aliud est
esse ens et aliud ipsum compositum quod est
participando ipsum esse.
Then when he says: In every composite etc., he
posits conceptions about the composite and the
simple, which pertain to the character of unity, and
it must be considered that those things said above
about the diversity of being (esse) itself and of
what-is (quod est), is according to the intentions
themselves. Here he shows how [this] is applied to
things; and first he shows this about composites,
second about simples, where [he says]: Every
simple etc.
Therefore first it must be considered that just as
being (esse) and what is (quod est) differ according
to intention, so also in composite [things] they
differ really. Indeed this is manifest from what
preceded. For it was said above that being (esse)
itself neither participates anything as though its
ratio were constituted from many, nor does it have
something extrinsic admixed with it as though
there were in it accidental composition; and
therefore being (esse) itself is not composite;
therefore a composite thing is not its esse; and
therefore he says that in every composite it is one
thing to be a being (esse ens) and another to be the
composite itself, which is, by participating ipsum
esse.
The most famous text concerning the distinction of essence and esse, that found in c. 4 of
the De ente et essentia.42 We can distinguish two stages in the argument presented in this text. The
first stage presents a version of what is often called St. Thomas’s intellectus essentiae
(understanding of an essence) argument. The context of this passage is that St. Thomas is
commenting on the characteristics of simple, intelligible essences (i.e., angels).43
42See Wippel 137-150 for
43All quotations are from the Goodwin translation.
Carl: Metaphysics 38
Stage 1: intellectus essentiae argument
Even though intelligences are simple (or non-composite) insofar as they are not composed
of matter and form, nevertheless St. Thomas wants to argue that there is some potency in them,
such that they are not pure act. (As we will explain later, St. Thomas holds that God alone is
absolutely pure act without any admixture of potency). St. Thomas now begins to offer his
argument for the claim that intelligences are composite in some way:
St. Thomas’s argument begins with the assertion that a given essence includes as
intelligible parts all of those things without which that essence cannot be understood. For example,
rational, animal, flesh, and bones are all intelligible parts of the essence of man: one does not
understand what a man is without knowing these parts of the essence. Anything that belongs to a
particular man besides these essential notes does so because of some kind of composition with
something extraneous to the essence of man. For example, that a man is white or tall or educated is
a matter of composition with these accidental forms.
Now St. Thomas notes that the esse of a thing is not one of these intelligible parts of an
essence, because one can understand what an essence or quiddity is without having an
understanding of its existence. One can know what a man is or what a phoenix is without knowing
whether these essences exist. Therefore esse is not a part of the essence of either of these things,
and in general St. Thomas reaches the conclusion that esse is not a part of any essence of which
human beings have some understanding.
Concerning the phoenix
What are we to take St. Thomas to mean by this example of the phoenix? One common
way of interpreting this passage is to treat the phoenix as an instance of a chimera, that is, of a
possible essence that does not actually exist. On this reading, St. Thomas is asserting that one can
understand the essence of something that does not, never has, and never will actually exist.
Understanding St. Thomas’s example in this way, a number of commentators have offered the
criticism that it seems problematic to say that we can possess understanding of such a non-existent
possible essence. It seems impossible that we should know the essence of a thing that does not
exist. Furthermore, it seems problematic to reason from an assertion about the understanding of
On the other hand, every essence or quiddity can be understood without its esse being understood.
I can understand what a man or phoenix is, and yet not know whether or not it exists in the nature
of things. Therefore, it is evident that the act of existing is other than essence or quiddity.
Although substances of this kind are simply forms without matter, nonetheless they are not in
every way simple, as pure acts are. They do have an admixture of potency, which is evident in the
following way.
Whatever is extraneous to the concept of an essence or quiddity is adventitious, and forms a
composition with the essence, since no essence can be understood without those things which are
its parts.
Carl: Metaphysics 39
non-existent possibles to a claim about the metaphysical structure of real being.
We can articulate the problem posed by this interpretation in terms of Aristotle’s scientific
questions, which are treated at the beginning of Posterior Analytics II.
(1) an est – if it exists / does the subject exist / whether it is
-The first scientific question concerns whether the subject to be studied exists.
Typically, in the case of the chief sciences, this question is answer not by
argument, but immediately from sense experience.
-In order to answer this question, one must first possess a nominal understanding
of what the thing in question is: that is, one must understand what the thing’s name
signifies.
(2) quid est – what is it / what is the essence or quiddity
-The second scientific question concerns the essence or quiddity of the subject
studied. The answer to the question quid est is expressed through terms that can be
essentially predicated of the subject (i.e., genera, species, and difference), and most
properly through the real definition of its species.
-Aristotle and St. Thomas both emphasize that once one knows that something
exists (answering an est affirmatively), one always asks what it is (quid est).
Furthermore, they also claim that one must know that something exists before one
can reasonably inquire into what it is, in this strict sense. This requirement is
grounded in their epistemological thesis that all human knowledge is derived
ultimately from the senses.
[(3) utrum est / quia – whether it is such and such / that it is so
-The third scientific question concerns the predication of something about the
subject studied. That is, this question possesses a more complex structure than the
first two questions. One can best understand this question as pertaining to the
properties of the subject, as distinct from its essence, which is expressed in the
definition as an answer to the question quid est.
(4) propter quid – why is it such and such
-The fourth question is the proper question of science in the strict sense: it is the
question answered by the demonstration, in which one expresses in a syllogism the
relationship of cause to effect, answering why it is that a subject possesses a
property (the answer to the question utrum est) with an argument that employs the
essence of the subject (the answer to quid est) as a middle term.]
The example of the phoenix, if interpreted as a chimera (i.e., as something that never
actually exists but that only exists as a being of reason), suggests that we could know the answer to
the question quid est without having previously established an affirmative answer to the question
an est. It seems much more reasonable to say that while we may know what the name phoenix
signifies (i.e., a mythical bird, of which there is only one, that is consumed by fire at death and is
later reborn from the ashes), this does not count as quidditative knowledge (i.e., as a grasp of what
the phoenix really is in itself).
However, the example need not be taken in this way at all (i.e., as asserting that we possess
quidditative knowledge of a non-existent entity), given what a phoenix is supposed to be. A
phoenix is a mythical bird possessing the following characteristics: (1) there is only one phoenix;
(2) the phoenix lives for a period of time, and at the end of its life it is consumed by fire and
Carl: Metaphysics 40
reduced to ashes; (3) for a period of time, the phoenix no longer exists, until it is reborn from the
ashes.
Although it is not necessarily the case that St. Thomas himself believed that the phoenix is
real, there were many among medieval Christians who did think that the phoenix was real. In any
event, in picking the example of the phoenix, St. Thomas has not selected a mere chimera; he has
selected a chimera that some people thought to be real, and a chimera that has various
characteristics relevant for its use as an example in this context. That is, a phoenix is an animal that
is supposed to exist at some times and not at others; and since there is only one phoenix, if the one
phoenix does not exist, then no phoenix exists.44 Thus one could understand what a phoenix is
without knowing anything about whether it exists. Therefore, St. Thomas concludes, it cannot be
the case that esse is included as an intelligible part of the essence of the phoenix. It seems, then,
more reasonable to think that St. Thomas included the example of the phoenix not insofar as it is a
chimera, but as a supposed essence that at certain times does not exist.
What is established by the first stage of this argument?
Even taking the example of the phoenix as we have just suggested, the question arises as to
what exactly this argument establishes. That the understanding of an essence does not include esse
at a minimum establishes that there is a distinction between essence and esse, between what
something is and its actual existence. However, is this distinction necessarily a real distinction in
an extramental thing, even apart from the consideration of the mind?
On the one hand, it seems that St. Thomas may understand even this first stage of his
argument to establish real composition of essence and esse: he contends that “whatever is
extraneous to the concept of an essence or quiddity is adventitious, and forms a composition with
the essence.” However, many recent Thomistic scholars have called into question whether the
intellectus essentiae argument can truly establish a real distinction and composition between
essence and esse.45 In particular, Msgr. Wippel brings up that St. Thomas is very clear elsewhere in
asserting that we cannot possess quidditative knowledge of separate substances (the subject under
direct examination in this text from the De ente), and he also expresses serious reservations about
our capacity for comprehensively grasping even the quiddities of corporeal substances.46 If we
cannot comprehensively grasp either simple essences or the essences of corporeal substances, then
the fact that esse is not included in our understanding of any essence does not necessarily mean
that esse is not a part of that essence: it may just be that we know that essence (and every essence)
imperfectly. As Msgr. Wippel points out, the intellectus essentiae argument disappears from St.
Thomas’s later writings, and so perhaps St. Thomas himself came to recognize that it could not
establish a real distinction and composition, but only a logical distinction.
Stage 2: the impossibility of more than one being in which essence and esse are the same
Having given an initial argument for the composition and distinction of essence and esse in
44Jean Buridan, a later critic of St. Thomas’s arguments in favor of real distinction of essence and esse,
understands the purpose of the example of the phoenix in the way suggested here; in his analysis of the
intellectus essentiae argument, he replaces the phoenix with the rose and thunder, two realities that exist
only some of the time. I take this comparison between Buridan and St. Thomas from Gyula Klima,
“Parvus Error in Principio Magnus est in Fine,” a paper given at The Metaphysics of Aquinas and the
Modern Retrieval of Medieval Thomism, March 26, New York, NY. The paper’s publication is
forthcoming.
45See Wippel 140-43.
46Wippel 142.
Carl: Metaphysics 41
simple substances, St. Thomas proceeds to a second stage in his argument, in which he
acknowledges the possibility of a being in which essence and esse are not distinct:
That essence and esse are distinct in all things is true unless, perhaps, there is something
whose very quiddity is its esse. If such a thing exists, it would have to be unique and primary (or
first). To argue for this conclusion, St. Thomas offers an account of the various ways in which a
reality can be multiplied.
Ways in which something can be multiplied:
(1) By the addition of a difference, as a genus is multiplied into various species. What
distinguishes the species of a genus are the differences of those species.
(2) By the reception of a form into diverse matter, as a species (such as man) is multiplied
in distinct individuals. (We will examine this claim later, that a species is individuated by matter.)
(3) By being something absolute so as to be distinguished from what is received in
something else. St. Thomas suggests an example: if there were a separate heat that was not the heat
of anything, then it would be distinct from the heat that is an accident of something. However,
there could only be one such separate heat, since nothing would serve to distinguish a separate heat
from another separate heat. St. Thomas’s point with this kind of multiplicity is that two things can
be diverse even without belonging to a common genus or species. (As we will see, this is how St.
Thomas will explain God’s being distinct from other things: He is distinct from other things even
without sharing in a genus or species with them).
St. Thomas then proceeds to explain why a being in which essence and esse are identical
could not be multiplied in any of the ways indicated above.
This is true, unless, perhaps, there is something whose quiddity is its very esse. This thing would
have to be unique and primary, since it would be impossible for anything to be multiplied except
by the addition of some difference, as the nature genus is multiplied into species; or by a form
received in diverse matters, as the nature species is multiplied in different individuals; or by one
being absolute, and the other being received in something. For example, if there were a certain
separated heat it would be distinct, in virtue of its very separation from the heat which is not
separated.
If, however, something is posited which is simply its own act of existence such that it would be
subsistent existence itself, this existence cannot receive the addition of a difference, because then it
would not be simply an act of existing, but an act of existing plus this certain form. Even less
would it receive the addition of matter, because then it would not be subsistent existence, but
material existence. Hence, there remains only one such thing that is its own act of existing.
Carl: Metaphysics 42
It is not possible for the suggested subsistent esse to be multiplied in either of the first two
ways distinguished above. The first way, multiplication by the addition of a difference, is not
possible, because then the essence of the being in question would no longer be simply esse, but
esse plus the difference. (Similarly, a dog is not merely or simply an animal, precisely because its
essence is differentiated from the genus animal.)
The second way, multiplication of a species by reception of form into matter, would
similarly make the suggested subsistent esse to be no longer simply or purely esse, but esse plus
matter. This is an even more difficult suggestion, because then the esse in question would be
material being: but esse is not restricted to material being, as is established by the judgment of
separation.
As for the third way in which something can be multiplied, St. Thomas does not offer any
direct commentary concerning whether this kind of multiplication could occur in the case of
subsistent esse, but implicitly he accepts that subsistent esse would be distinguished from all other
things just be being esse absolutely, while esse in everything else is something distinct from its
essence and received in it. As noted above, this third mode of multiplication allows only for one
instance of the separate and absolute form, and this is precisely what St. Thomas intends to
establish concerning subsistent esse: there can only be one such being. This allows St. Thomas to
conclude his argument in favor of real distinction and composition of essence and esse:
There can be at most one being in which essence and esse are identical, so that its essence
is its very act of existence. In every other thing, esse (understood as the act of existence) and the
essence or quiddity must be distinct. St. Thomas then applies this conclusion to the intelligences,
concluding that in them act of existence must be distinct from form. We can add a point that St.
Thomas makes explicit elsewhere, that the act of existence is related as a principle of actuality to
the essence, which is in potency to receive the act of existence.
Does this argument presuppose God’s existence?
Among those scholars who acknowledge that St. Thomas posits a real distinction and
composition of esse and essence in created things, there is a dispute about whether St. Thomas’s
arguments for this thesis depend upon previously having demonstrated the existence of God. There
is in particular disagreement about the text from the De ente et essentia treated above. As we have
interpreted the argument, it does not depend upon any previously established claim concerning
God’s existence. The suggestion of a being in which essence and esse are identical is, at this point
in the argument, only a hypothetical. Nevertheless, in other contexts (such as Summa contra
Accordingly, in anything other than it, the act of existing must necessarily be other than its
quiddity or nature or form. Hence, among the intelligences, their acts of existing must be other than
their forms.
Carl: Metaphysics 43
Gentiles II c. 52, which Msgr. Wippel treats in his book, pp. 151-53), St. Thomas does take God’s
existence for granted (and the identity of essence and esse in God) in arguing for the real
distinction and composition of essence and esse in creatures.
6.3. The Suggestion of God’s Existence from the Real Composition of Essence and Esse
Not only is it the case that the argument for real distinction given in the De ente et essentia
c. 4 does not presume God’s existence; instead, St. Thomas uses the distinction between essence
and esse in creatures in order to immediately offer a brief argument for the existence of God:
This section of the De ente et essentia (which Msgr. Wippel also calls the third stage of the
argumentation concerning essence and esse) presents an argument for the existence of the being in
which essence and esse are identical. The argument proceeds from the assertion that whatever a
thing has must be caused either by the intrinsic principles of the thing or by some extrinsic agent. If
this assertion is accepted, then it follows that whatever has esse (the act of existing) but is not
identical with it must have its esse caused by something, either by its own intrinsic principles or by
an extrinsic agent. But it is impossible that a thing’s esse should be caused by its intrinsic
principles, because then a thing would be the cause of its own existence, which is absurd, because
something must exist in order to be a cause.47 It remains, then, that anything in which essence and
47St. Thomas clarifies that this claim about causing existence is restricted to efficient causality, because he
Whatever belongs to something is either caused by the principles of its nature, like risibility in
man, or accrues to it from some extrinsic principle, like the light in the air, which is caused by the
sun. It is impossible that the act of existing itself be caused by the form or quiddity—and by
“caused” I mean as by an efficient cause—for then something would be the cause of itself and
produce itself in existence, which is impossible. It is therefore necessary that everything whose act
of existing is other than its nature have its act of existing from another. And because everything
which exists through another is reduced to that which exists through itself, as to a first cause, there
must be something which causes all things to exist, inasmuch as it is subsistent existence alone.
Otherwise we would proceed to infinity in causes, since everything which is not a subsistent act of
existing has a cause for its act of existing, as we have just said. It is evident, therefore, that an
intelligence is a form and an act of existing and that it has its act of existing from the First Being
which is existence only; and this is the First Cause, God.
Carl: Metaphysics 44
esse are really distinct must have its act of existence caused by some extrinsic efficient cause. One
must therefore arrive at some first cause of the existence of all other things, a being in which
essence and esse are identical, and St. Thomas remarks that this First Being and First Cause is
God.
does hold that a thing’s substantial form is a cause of its esse—but a formal cause rather than an efficient
cause.
Carl: Metaphysics 45
6.4. Other Ways of Arguing for Essence-Esse Composition
Besides the forms of argument that we have identified in the two stages of c. 4 of the De
ente et essentia (the intellectus essentiae argument and the argument from the impossibility of
there being more than one being whose essence is its very esse), St. Thomas offers a number of
other arguments in favor of essence-esse composition in finite substances. We will consider at least
one textual example for each of the three other varieties of argument identified by Msgr. Wippel.
The “genus” argument48
As Msgr. Wippel explains, St. Thomas frequently claims and argues that whatever belongs
to a genus must be composed of essence or quiddity and esse. Most often, this sort of claim
appears in the context of argumentation supporting the thesis that God is not in any genus. For
example, in ST 1.3.5, St. Thomas argues as follows:
Tertio, quia omnia quae sunt in genere uno,
communicant in quidditate vel essentia generis,
quod praedicatur de eis in eo quod quid est.
Differunt autem secundum esse: non enim idem est
esse hominis et equi, nec huius hominis et illius
hominis. Et sic oportet quod quaecumque sunt in
genere, different in eis esse et quod quid est, idest
essentia. In Deo autem non differt, ut ostensum est.
Unde manifestum est quod Deus non est in genere
sicut species.
Third, since all those that are in one genus share in
the quiddity or essence of the genus, which is
predicated of them as what-it-is. But they differ
with regard to being (esse): for the being (esse) of
a man is not the same as [that] of a horse, nor [the
being] of this man and of that man. And thus it
must be that whatever [things] are in a genus, in
them being (esse) and what-it-is (quod quid est),
that is essence. But in God it does not differ, as
was shown. Wherefore it is manifest that God is
not in a genus as a species.
Being—in the sense of existence or the act of being—is not the same in man or in horse,
nor in this man and in that man. If one needs an argument for this claim, one need only consider
that a man can continue to exist even if a horse or another man should cease to exist: and what is
separable in this way is not the same.49 But the many men and the many horses do share in the
quiddity or essence of the genus animal (just as they each also share in their respective species).
Therefore, esse and essence must differ in them.
It might be questioned whether this formulation of the argument establishes a real
distinction between esse and essence, since it depends upon the essence of the genus in which
members of a given genus share—and the distinction of the genus itself from the individual is a
logical distinction rather than a real distinction.50
48Wippel 157-61.
49Whereas we want to emphasize that real distinction (or composition) does not imply separability (i.e., the
possible existence of one item without the other), nevertheless separability always implies real
distinction. In this case, that a man can exist independently of a horse serves to indicate that the existence
or act of being of the man is not the same as the existence or act of being of the horse.
50See Wippel 161, in which Msgr. Wippel gives his evaluation of the “genus” argument, judging that as this
argument is formulated by St. Thomas, it is not sufficient to establish a real composition or distinction of
esse and essence; rather, it needs support from other metaphysical theses against objections. My purpose
in these next few paragraphs is to indicate some possible ways of supporting the “genus” argument
Carl: Metaphysics 46
To this objection, it can be replied that although the genus animal itself does not exist
outside the mind, and although animal is only logically distinct from Alexander or Bucephalus,
nevertheless Alexander and Bucephalus are generically identical in reality. The logical distinction
of the genus animal has its foundation in what this individual animal and that individual animal
really share in common. So, when it is argued that the essence of animal is the same in Alexander
and Bucephalus, this is not to be understood as a claim about sameness that is merely logical,
intentional, and posterior to the activity of the mind. Therefore, that Alexander and Bucephalus
really share in the essence of animal (or that Aristotle and Alexander really share in the species
man), but differ in their existences or acts of being, seems sufficient to establish the real distinction
of these principles in these individuals.
Yet, it might still be objected that this formulation of the “genus” argument does not
concern the individual essence—that is, the essence of this individual—but only concerns essence
taken as a universal, as what is common to many. Even if Alexander and Bucephalus are
generically the same (or Alexander and Aristotle are specifically the same), still they differ
numerically: and perhaps existence or the act of being (esse) is part of the individual essence of
each of these individuals, without it being the case that esse really differs from or is composed with
the individual essence.
To answer this objection, we need to make reference to two theses that we will articulate in
full and defend later. The first concerns the principle of individuation—that is, the principle that
serves to diversify a species into its many individuals. As we shall later see, St. Thomas holds that
the principle of individuation is designate matter. According to this thesis, Socrates differs from
Plato, because Socrates has this flesh and these bones, whereas Plato has that flesh and those
bones. Flesh and bones, taken universally, belong to the essence of man taken universally; but the
individual essence of Socrates includes his designate matter, as distinguished from matter in the
abstract. The second thesis concerns the character of form as a principle: according to St. Thomas,
a thing’s form gives it its esse, because the formal cause is by definition that which makes a thing
to be (esse) what it is.
Now, according to the first of these theses, the essence of man taken as a universal is
contracted to the individual by designate matter, which is a principle of potency relative to the
human form. According to the second thesis, it is by virtue of a thing’s form that it exists or has
esse. To conclude that esse is a part of the individual essence would therefore suggest that esse (or
the act of being) is the designate matter of a thing; but it is form and not matter that gives esse, and
so it cannot be the case that esse is a part of the individual essence. Therefore, the individual
essence and esse must differ really.
That St. Thomas understands the “genus” argument to establish a real distinction and
composition of essence and esse is clear from a second text in which he employs this form of
argumentation, DV 27.1 ad 8. In this context, St. Thomas employs a form of the “genus” argument
in a different context, in order to argue that grace can be something created and accidental, despite
the fact that grace is a simple form. Although this text’s purpose is explicitly theological, the
presentation of the “genus” argument is itself philosophical in character. In this text, St. Thomas
writes:
Ad octavum dicendum, quod omne quod est in
genere substantiae, est compositum reali
To the eighth it is said that whatever is in the genus
of substance is composed by a real composition;
against objection.
Carl: Metaphysics 47
compositione; eo quod id quod est in
praedicamento substantiae est in suo esse
subsistens, et oportet quod esse suum sit aliud
quam ipsum, alias non posset differre secundum
esse ab illis cum quibus convenit in ratione suae
quidditatis; quod requiritur in omnibus quae sunt
directe in praedicamento: et ideo omne quod est
directe in praedicamento substantiae, compositum
est saltem ex esse et quod est.
Sunt tamen quaedam in praedicamento substantiae
per reductionem, ut principia substantiae
subsistentis, in quibus praedicta compositio non
invenitur; non enim subsistunt, ideo proprium esse
non habent. Similiter accidentia, quia non
subsistunt, non est eorum proprie esse; sed
subiectum est aliquale secundum ea; unde proprie
dicuntur magis entis quam entia.
Et ideo, ad hoc quod aliquid sit in praedicamento
aliquo accidentis, non requiritur quod sit
compositum compositione reali, sed solummodo
compositione rationis ex genere et differentia: et
talis compositio in gratia invenitur.
because that which is in the predicament of
substance is subsisting in its act of being (esse),
and it must be that its act of being (esse) is other
than [the thing] itself; otherwise it could not differ
in the act of being (esse) from those [things] with
which it shares in the intelligibility (ratio) of its
quiddity, which is necessary in all those which are
directly in the predicament: and therefore whatever
is directly in the predicament of substance, is
composed at the least of the act of being (esse) and
what-is (quod est).
But there are some things in the predicament of
substance by reduction, such as the principles of a
subsistent substance, in which the aforementioned
composition is not found; for they do not subsist,
and therefore do not have their own act of being.
Similarly accidents, because they do not subsist, of
them there is not their own act of being; but the
subject is some way because of them; wherefore
they are more properly said [to be] “of a being”
rather than beings.
And therefore, for this that something be in some
predicate of accident, it is not required that it be
composite by a real composition, but only by a
composition of reason from genus and difference:
and such a composition is found in grace.
St. Thomas begins with a version of the “genus” argument that avoids some of the
difficulty suggested by the formulation found in ST 1.3.5: in this text from the De veritate, he
offers his argument in terms of what belongs to the category of substance and therefore shares in
the ratio of the quiddity of substance. He explicitly states that the composition of what-is and esse
in all members of the category of substance is a real composition, and this is distinguished in the
third paragraph from a composition of reason by genus and difference.
Once again, the “genus” argument itself proceeds from the sameness in essence but
difference in esse among members of a genus, but in this case the argument is restricted to the
genus of substance. Because a given substance is the same as another substance insofar as both
share in the intelligible content of the quiddity of substance, but one substance differs in its esse
Carl: Metaphysics 48
from another substance, it must be that in each substance there is a composition of quiddity and
esse—or as St. Thomas expresses it here, of what-is (being in the sense of ens) and esse.
In the second paragraph of this text, St. Thomas adds some helpful points of clarification.
By the principles of a substance, St. Thomas means its form and its matter (at least for those
substances that are composed of form and matter): this substance’s substantial form and prime
matter belong to the category of substance by reduction, but form and matter are not themselves
composed of essence and esse. As we will explain later, in our discussion of form-matter
composition, for St. Thomas the essence of a corporeal substance includes both form and matter,
whereas the essence of a separate substance is form alone. Furthermore, accidents do not admit of
the same composition of essence and esse, because they exist insofar as they modify substance,
rather than subsisting independently.
Arguments based on participation51
We have already seen one example of an argument in which St. Thomas proceeds from the
participation of ens in esse to a claim about the real composition of ens, in Exp. De ebd. lec. 2, a
text that we can consider anew:
Deinde cum dicit: Omni composito etc., ponit
conceptiones de composito et simplici, quae
pertinent ad rationem unius, et est considerandum
quod ea quae supra dicta sunt de diversitate ipsius
esse et eius quod est, est secundum ipsas
intentiones. Hic ostendit quomodo applicetur ad
res; et primo ostendit hoc in compositis, secundo
in simplicibus, ibi: Omne simplex etc.
Est ergo primo considerandum quod sicut esse et
quod est differunt secundum intentiones, ita in
compositis differunt realiter. Quod quidem
manifestum est ex praemissis. Dictum est enim
supra quod ipsum esse neque participat aliquid ut
eius ratio constituatur ex multis, neque habet
aliquid extrinsecum admixtum ut sit in eo
compositio accidentalis; et ideo ipsum esse non est
compositum; res ergo composita non est suum
esse; et ideo dicit quod in omni composito aliud est
esse ens et aliud ipsum compositum quod est
Then when he says: In every composite etc., he
posits conceptions about the composite and the
simple, which pertain to the character of unity, and
it must be considered that those things said above
about the diversity of being (esse) itself and of
what-is (quod est), is according to the intentions
themselves. Here he shows how [this] is applied to
things; and first he shows this about composites,
second about simples, where [he says]: Every
simple etc.
Therefore first it must be considered that just as
being (esse) and what is (quod est) differ according
to intention, so also in composite [things] they
differ really. Indeed this is manifest from what
preceded. For it was said above that being (esse)
itself neither participates anything as though its
ratio were constituted from many, nor does it have
something extrinsic admixed with it as though
there were in it accidental composition; and
therefore being (esse) itself is not composite;
therefore a composite thing is not its esse; and
51Wippel 161-70.
Carl: Metaphysics 49
participando ipsum esse. therefore he says that in every composite it is one
thing to be a being (esse ens) and another to be the
composite itself, which is, by participating ipsum
esse.
This argument is restricted to composite things (that is, to composites of matter and form).
St. Thomas argues that being (esse) itself is not composite in any way, and so there must be a lack
of real identity between the composite being (ens) and its existence or act of being (esse). Having
given this argument, St. Thomas proceeds to consider an argument that will also pertain to simple
substances (i.e., to angels):
Deinde cum dicit: Omne simplex etc., ostendit
qualiter se habeat in simplicibus in quibus necesse
est quod ipsum esse et id quod est sit unum et idem
realiter. Si enim esset aliud realiter id quod est et
ipsum esse, iam non esset simplex sed
compositum. Est tamen considerandum quod, cum
simplex dicatur aliquid ex eo quod caret
compositione, nihil prohibet aliquid esse secundum
quid simplex, in quantum caret aliqua
compositione, quod tamen non est omnino
simplex; unde et ignis et aqua dicuntur simplicia
corpora, in quantum carent compositione quae est
ex contrariis quae invenitur in mixtis, quorum
tamen unumquodque est compositum, tum ex
partibus quantitativis, tum etiam ex forma et
materia. Si ergo inveniantur aliquae formae non in
materia, unaqueque earum est quidem simplex
quantum ad hoc quod caret materia, et per
consequens quantitate quae est dispositio materiae.
Quia tamen quaelibet forma est determinativa
ipsius esse, nulla earum est ipsum esse, sed est
habens esse; puta secundum opinionem Platonis,
ponamus formam immaterialem subsistere quae sit
idea et ratio hominum materialium, et aliam
formam quae sit idea et ratio equorum, manifestum
erit quod ipsa forma immaterialis subsistens, cum
Then when he says: Every simple etc., he shows
how it is in simple [things] in which it is necessary
that being itself and that-which-is be one and the
same really. For if that-which-is and being (esse)
itself were other, then it would not be simple but
composite. Nevertheless it must be considered that,
since something is called simple from this that it
lacks composition, nothing prohibits something
from being simple in a qualified way (secundum
quid), insofar as it lacks some composition, which
is nevertheless simple in every way; whence both
fire and water are called simple bodies, insofar as
they lack the composition from contraries which is
found in mixed [bodies]; nevertheless each of these
[(fire and water)] is composite, both from
quantitative parts and also from form and matter. If
therefore there be found some forms not in matter,
each of these is indeed simple insofar as it lacks
matter, and consequently quantity, which is a
disposition of matter. Nevertheless since each form
is determinative of being (esse) itself, none of
these is being (esse) itself, but is [something]
having being (habens esse); for instance according
to the opinion of Plato, should we posit as
subsisting an immaterial form which is the idea
and intelligibility of material men, and another
Carl: Metaphysics 50
sit quiddam determinatum ad speciem, non est
ipsum esse commune, sed participat illud. Et nihil
differt quantum ad hoc si ponamus alias formas
immateriales altioris gradus quam sint rationes
horum sensibilium ut Aristoteles voluit;
unaquaeque enim illarum, in quantum distinguitur
ab alia, quaedam specialis forma est participans
ipsum esse, et sic nulla earum erit vere simplex. Id
autem solum erit vere simplex quod non participat
esse, non quidem inherens sed subsistens. Hoc
autem non potest esse nisi unum, quia, si ipsum
esse nihil aliud habet admixtum praeter id quod est
esse, ut dictum est, impossibile est id quod est
ipsum esse multiplicari per aliquid diversificans,
et, quia nihil aliud praeter se habet adiunctum,
consequens est quod nullius accidentis sit
susceptivum. Hoc autem simplex, unum et sublime
est ipse Deus.
form which is the idea and intelligibility of horses,
it would be obvious that the subsisting immaterial
form itself, since it is determined to a species, is
not common being itself (ipsum esse commune),
but participates it. And nothing would change
about this if we should posit other immaterial
forms of a higher grade than the intelligibilities of
these sensible [things], as Aristotle wished; for
each of those, insofar as it is distinguished from the
others, is a certain special form participating being
(esse) itself, and thus none of these will be truly
simple. But that alone will be truly simple which
does not participate being (esse), indeed not
inhering but subsisting. But this cannot be but one,
if being (esse) itself has nothing else admixed
besides what-it-is-to-be, as was said, it is
impossible that what-it-is-to-be be multiplied
through something diversifying [it], and since
nothing else is adjoined to it, consequently it is
susceptible to no accidents. But this simple, one
and sublime, is God Himself.
In this argument, St. Thomas combines elements of what we above called the argument
from the impossibility of there being more than one thing in which essence and esse are identical
with the language of participation. He distinguishes between what is absolutely simple (omnino
simplex) and what is simple in a qualified or relative way (simplex secundum quid). As he proceeds
to explain, God alone is absolutely simple, whereas other things (including both angels and even
certain bodies, such as the elements) are called simple only in a qualified or relative way. If one
posits immaterial forms, whether these are Platonic Forms or Aristotelian separate substances,
these will be determined to species and will differ from one another, and as a consequence they
will be said to participate esse rather than to be identical with being itself. As we will later explain
in our discussion of form-matter composition, it pertains to the formal cause to determine and limit
esse, as St. Thomas notes here. As a consequence, even in a pure form without matter, essence or
form will be other than the esse that it determines and limits: it will not be esse itself.
Argument based on the limited character of individual beings52
A final category of argument for essence-esse composition is what Msgr. Wippel calls the
argument based on the limited character of individual beings. This form of argument appears
explicitly and independently in only one text: In Sent. 1.8.5.1. In this article, St. Thomas asks
whether any creature is simple. As we have seen in the previous text we considered, St. Thomas
distinguishes between what is simple in every way (omnino simplex) and what is simple in a
52Wippel 170-76.
Carl: Metaphysics 51
qualified way (simplex secundum quid). In In Sent. 1.8.5.1, St. Thomas is concerned with the
former, absolute kind of simplicity, and he argues that no creature is simple in this way.
Praeterea, omnis creatura habet esse finitum. Sed
esse non receptum in aliquo, non est finitum, immo
absolutum. Ergo omnis creatura habet esse
receptum in aliquo; et ita oportet quod habeat duo
ad minus, scilicet esse, et id quod esse recipit.
Furthermore, every creature has finite being (esse).
But being (esse) not received in something is not
finite, but absolute. Therefore every creature has
being (esse) received in something else; and so it is
necessary that it have at least two [components],
namely being (esse) and that which receives being
(esse).
This interesting argument depends upon two other claims: (1) a creature’s being is finite,
and (2) unreceived esse is absolutely unlimited. The former claim receives no special
argumentation in this text, and as Msgr. Wippel notes, it is a claim that St. Thomas is willing to
take for granted. The latter claim seems to be axiomatic for St. Thomas. As an axiom, it must
depend upon the notion of esse: So what is it about the notion of esse that implies that esse as such
is unlimited, or that it is not self-limiting?
We will conclude our treatment of essence-esse composition with reference to one of the
most famous texts of St. Thomas, in which he succinctly states what he understands as central to
the notion of esse or the act of being. This text is De potentia q. 7 a. 2 ad 9:
Ad nonum dicendum, quod hoc quod dico esse est
inter omnia perfectissimum: quod ex hoc patet
quia actus est semper perfectior potentia. Quaelibet
autem forma signata non intelligitur in actu nisi per
hoc quod esse ponitur. Nam humanitas vel igneitas
potest considerari ut in potentia materiae existens,
vel ut in virtute agentis, aut etiam ut in intellectu:
sed hoc quod habet esse, efficitur actu existens.
Unde patet quod hoc quod dico esse est actualitas
omnium actuum, et propter hoc est perfectio
omnium perfectionum. Nec intelligendum est,
quod ei quod dico esse, aliquid addatur quod sit eo
formalius, ipsum determinans, sicut actus
potentiam: esse enim quod huiusmodi est, est aliud
secundum essentiam ab eo cui additur
determinandum. Nihil autem potest addi ad esse
quod sit extraneum ab ipso, cum ab eo nihil sit
extraneum nisi non-ens, quod non potest esse nec
To the ninth it is said that this which I call esse is
the most perfect among all [perfections]: which
follows from this, that act is always more perfect
than potency. Now each designate form is not
understood in act except through this that it is
posited to be. For humanity or fieriness can be
considered as existing in potency in matter, or as in
the power of an agent, or even as [it is] in the
intellect: but what has esse is made an existent in
act. Whence it follows that this which I call esse is
the actuality of every act, and because of this it is
the perfection of every perfection. Nor should it be
understood that to what I call esse is anything more
formal than it added, determining it, as act [is more
formal than and determines] potency: for esse in
this sense is essentially other from that to which it
is added [so as] to be determined [by it]. Now
nothing can be added to esse which is extraneous
Carl: Metaphysics 52
forma nec materia. Unde non sic determinatur esse
per aliud sicut potentia per actum, sed magis sicut
actus per potentiam.
to it, since nothing is extraneous to it except nonbeing, which cannot be either form or matter.
Whence esse is not thus determined by another as
potency [is determined] by act, but rather as act [is
determined] by potency.
Esse is described here as the actuality of every act and the perfection of every
perfection. St. Thomas argues that this follows from the fact that a given designate form (that is,
the form of this thing) may exist potentially in matter, or virtually in the agent that can cause this
form, or even in the intellect: but the designate form is never understood in act unless it is
understood or supposed to be. That is, the actual intelligibility of form is itself dependent upon
existence or the act of being (esse): and because a principle of intelligibility is always a formal
principle or act principle, St. Thomas concludes that esse is more formal than the form or essence,
that it is the actuality of every act and the perfection of every perfection.
Another way of putting this same insight about esse is to note, as St. Thomas does in ST
1.4.2, that the perfection of being is the most fundamental perfection and contains every other
perfection:
Omnium autem perfectiones pertinent ad
perfectionem essendi: secundum hoc enim aliqua
perfecta sunt, quod aliquo modo esse habent.
But all perfections pertain to the perfection of
being (esse): for things are perfect insofar as they
have being (esse) in some mode.
The actuality of any perfection whatsoever is existence (esse), because a thing is perfect
insofar as it exists or has being (esse) in some way. It is in light of such a claim about being (esse)
that St. Thomas can justifiably treat the claim encountered above—that esse is only limited by
being received—as an axiom or immediate principle. Esse is the actuality of every act and the
perfection of every perfection; it is more formal than form or essence and is only limited by the
form or essence taken as a principle of potency. We will have more to say about this issue when we
make general comments about the various modes of act-potency composition found in finite
beings, later in our course.
Carl: Metaphysics 53
7. Substance-Accident Composition
Having completed our lengthy discussion of essence-esse composition in all of the beings
falling under the subject of metaphysics, ens commune, we now turn to the other mode of
composition that St. Thomas holds to be common to all such beings: this is the composition of
substance and accident. We will treat a selection of the topics treated by Msgr. Wippel concerning
substance-accident composition, beginning with some of the points of clarification to be offering
concerning the meaning of substance.
7.1. What is Substance?
We have previously treated St. Thomas’s appropriation of the Aristotelian claim that
substance is the primary referent of the term being (ens), whereas accidents are beings in only a
secondary and dependent way. For Aristotle this claim is expressed in terms of pros hen
equivocation, whereas for St. Thomas this is a matter of analogical predication—to be precise,
what we previously distinguished as the horizontal or predicamental analogy.
In the Aristotelian Metaphysics, the pros hen equivocal character of being leads Aristotle to
a focus on substance as the primary referent of being. The question, “what is substance?” becomes
one of the central questions of the Metaphysics, with Aristotle addressing this question in terms of
form and matter, act and potency, and a focus on the highest instances of substance (the separate
substances). Although because of the limitations of time, we cannot present this material from the
Metaphysics itself, it must be acknowledged that most of what St. Thomas contends concerning
substance is indebted to Aristotle’s Metaphysics.
We considered above, in our treatment of the meaning of ens commune, a text from the
Commentary on the Metaphysics, Book V, in which St. Thomas has commented on the division of
ens into accidental being and essential being and the further division of essential being into being
in the categories and being in the mind. We now turn to the content of the following lectio of St.
Thomas’s Commentary, lec. 10. We should recall that Book V of the Metaphysics presents a
lexicon of metaphysical terminology: the subject of c. 8, about which lec. 10 comments, is the
meaning of substance.
In this text, St. Thomas follows Aristotle in distinguishing four meanings of the term
substance:
(1) first substance / primary substance, as this is treated in the Categories:
Circa primum ponit quatuor modos; quorum
primus est secundum quod substantiae particulares
sunt substantiae, sicut simplicia corpora, ut terra et
ignis et aqua et huiusmodi. Et universaliter omnia
corpora, etiam si non sint simplicia, sicut mixta
similium partium, ut lapis, sanguis, caro et
huiusmodi. Et iterum animalia quae constant et
huiusmodi corporibus sensibilibus, et partes
eorum, ut manus et pedes et huiusmodi. . . . Haec
Concerning the first, he posits four modes; of these
the first is [that] according to which particular
substances are substances, as the simple bodies,
such as earth and fire and water and others of this
kind. And universally all bodies, even if they are
not simple, such as mixed [bodies] of
homogeneous parts, such as stone, blood, flesh,
and others of this kind. And again animals which
are composed from sensible bodies of this kind,
Carl: Metaphysics 54
enim omnia praedicta dicuntur substantia, quia non
dicuntur de alio subiecto, sed alia dicuntur de his.
Et haec est descriptio primae substantiae in
praedicamentis.
and [animal’s] parts. . . . For all these mentioned
are called substance, because they are not said of
another subject, but others are said of these. And
this is the description of first substance in the
Categories.
In this text, St. Thomas provides a number of examples of primary substances, following
Aristotle’s text:
(a) the simple bodies
(b) homogeneous mixed bodies
(c) animals and their parts
[(d) the daemonia, mentioned by Aristotle in his text and briefly commented upon by St.
Thomas)]
These are called substance in the sense of first substance from Aristotle’s Categories, that
which is neither said of nor said to be in another, but rather that about which such things are said.
Concerning the second point, that in general homogeneous mixed bodies are substances, we have
noted previously in our course that for St. Thomas in this way things such as bread and wine are
substances, even though they only come to be by art.
(2) The intrinsic formal cause of the being of a first substance:
Dicit quod alio modo dicitur substantia quae est
causa essendi praedictis substantiis quae non
dicuntur de subiecto; non quidem extrinseca sicut
efficiens, sed intrinseca eis, ut forma. Sicut dicitur
anima substantia animalis.
He says that in another way [that] is called
substance which is the cause of being (causa
essendi) of the aforementioned substances which
are not said of a subject; and not extrinsic as an
efficient cause, but intrinsic to them, as a form.
Thus the soul is called the substance of an animal.
Aristotle contends that one may refer to the intrinsic formal cause—such as the soul of an
animal—as the substance of the thing. We will see what both he and St. Thomas do with this claim
shortly.
(3) The parts of substances that limit them and render them divisible:
We need not dwell on this division of substance, which is suggested by both Plato and
Pythagoras, for Aristotle and St. Thomas suggest it and proceed to dismiss it. In brief, the
suggestion is that the surface and lines of a thing are its substance, because the thing is destroyed
when its surfaces and lines are destroyed. Even though St. Thomas discusses this as a true meaning
of the term substance (because it confuses some of the properties of a body with the substance
itself), nevertheless it suggests that the term substance can be taken as referring to what is in some
way essential to a thing; and this suggests to us the fourth meaning of substance, as essence.
(4) The quiddity or essence of a thing:
Dicit quod etiam quidditas rei, quam significat He says also that the quiddity of a thing, which the
Carl: Metaphysics 55
definitio, dicitur substantia uniuscuiusque. Haec
autem quidditas sive rei essentia, cuius definitio est
ratio, differt a forma quam dixit esse substantiam
in secundo modo, sicut differt humanitas ab anima.
Nam forma est pars essentiae vel quidditas rei.
Ipsa autem quidditas vel essentia rei includit omnia
essentialia principia. Et ideo genus et species
dicuntur esse substantia eorum, de quibus
praedicantur, hoc ultimo modo. Nam genus et
species non significant tantum formam, sed totam
rei essentiam.
definition signifies, is called the substance of each
thing. But this quiddity or essence of a thing, of
which the definition is the intelligible content
(ratio), differs from the form which he said to be
substance in the second mode, as humanity differs
from the soul. For the form is part of the essence or
quiddity of the thing. But the quiddity or essence
itself of a thing includes all [its] essential
principles. And therefore the genus and species are
said to be the substance of those of which they are
predicated, in this last way. For the genus and
species do not signify form alone, but the whole
essence of a thing.
The example given of an essence—humanity—differs from the intrinsic form (such as the
soul) in that the essence includes the form but also includes the thing’s other essential principles.
Principally, St. Thomas has in mind matter. As we have said before, knowledge of the essence of
any corporeal substance includes a knowledge of both form and matter, albeit matter taken in the
abstract. In the second way, substance meant the intrinsic formal cause of the thing; in this fourth
way, substance is the essence or quiddity. It is also in this way that genus or species are said to be
the substance of a thing, because they signify not form alone, but the entire essence of a thing.
In his Commentary (and following Aristotle), St. Thomas reduces these four meanings of
substance to two. As already indicated, the third mode of substance is dismissed, leaving only
three; and St. Thomas combines the second and fourth modes, because the latter mode (essence)
includes the former (the intrinsic form). This leaves the following two modes:
(1) Substance as subject; primary substance; the suppositum or hypostasis53
(2) Substance as essence, quiddity, form54 or nature
Whenever one encounters the term substance in Aristotelian-Thomistic philosophy, one
must ask whether the term substance refers to the suppositum or to the essence.
Now, in the Categories, Aristotle draws a twofold distinction concerning substance into
primary substance and secondary substance, and at this point we must ask: is this division from the
Categories the same as the division of substance into suppositum and essence? The text from In
Meta. 5.10 might suggest that we should identify secondary substance with essence, insofar as it
said that it is in the fourth mode distinguished there that genus and species are called substance.
53See Wippel 203-204 for parallel texts in which St. Thomas draws the twofold division of meanings of
substance and refers to primary substance as suppositum and hypostasis.
54We mean by form here still the entire essence, rather than just the formal cause as distinguished from the
matter of the thing. As St. Thomas will put it elsewhere, essence is called form as the forma totius, to be
distinguished from the forma partis that is the substantial form.
Carl: Metaphysics 56
However, as Msgr. Wippel details (pp. 205-208), one should not identify the secondary
substance of the Categories with substance as essence or quiddity. As St. Thomas argues in De pot.
9.1, whereas the genus or species is predicated of a primary substance (in the language of the
categories, secondary substance is what is said of a primary substance), the essence cannot be
predicated of the individual. That is, while it is correct to say that Socrates is animal or man (his
genus and his species), it cannot be said that Socrates is humanity. This is the case because the
essence or nature is a formal part of the suppositum rather than being identical with the
suppositum, at least in the case of matter-form composites. We will have more occasion to discuss
this issue when we take up matter-form composition and the principle of individuation.
7.2. Derivation of the Ten Categories
One distinguishes substance from accident insofar as one distinguishes substance as the
primary mode of being from the other nine modes of being, the nine accidental modes. It is fitting
to consider at this time St. Thomas’s systematic exposition (or as Msgr. Wippel calls it, his
derivation) of the ten categories as modes of being.
A predicate can be related to a subject (with respect to what the predicate expresses) in
three ways:
1) the predicate is really identical with that which serves as the subject; for example,
“Socrates is animal.” “Here Socrates is that very thing which is an animal,” and animal
signifies the subject Socrates himself and what Socrates is, rather than anything accidental
about Socrates. This is the category of SUBSTANCE (1).
2) the predicate can be taken from something which is in the subject (this is how we have
broadly defined the accidents so far); but this in one of two ways:
a) the predicate can name something in the subject considered absolutely
i) but following upon the matter of the subject, in which case we have the
category of QUANTITY (2).
ii) but following upon the form of the subject, in which case we have the
category of QUALITY (3).
b) the predicate can be taken from something which is in the subject only
considered with reference to something else; this is the category of RELATION
(4).
3) the predicate can be derived from something extrinsic to the subject, and this in two
ways:
a) the predicate can be taken from something totally extrinsic to the subject
i) and if that from which the predicate is derived is not a measure of the
subject, then we have the category of HABIT (5).
ii) but if this predicate is taken from a measure of the subject, then we
have:
1) the category of TIME (or WHEN) (6), which is taken from the
extrinsic measure of time
2) the category of PLACE (or WHERE) (7), which is taken from
the extrinsic measure of place, without consideration of the
orientation of the parts of the subject
3) the category of POSITION (8), which is taken from the the
extrinsic measure of place, with consideration of the orientation of
the parts of the subject
Carl: Metaphysics 57
b) the predicate can be taken from something that is both outside the subject and
from a certain point of view also in the subject of which it is predicated:
i) and if the subject is the principle of what is extrinsic, then it is
predicated in the category of ACTION (9)
ii) and if the subject is the terminus of what is extrinsic, then it is
predicated in the category of PASSION (10).55
St. Thomas’s systematic treatment of the ten categories according to ten modes of
predication depends upon the more fundamental claim that these various modes of predication
depend upon diverse modes of being in things. In the text introducing the derivation of the
categories just treated, St. Thomas writes:
Dicit ergo primo, quod illa dicuntur esse secundum
se, quaecumque significant figuras praedicationis.
Sciendum est enim quod ens non potest hoc modo
contrahi ad aliquid determinatum, sicut genus
contrahitur ad species per differentias. Nam
differentia, cum non participet genus, est extra
essentiam generis. Nihil autem posset esse extra
essentiam entis, quod per additionem ad ens
aliquam speciem entis constituat: nam quod est
extra ens, nihil est, et differentia esse non potest.
Unde in tertio huius probavit Philosophus, quod
ens, genus esse non potest.
Unde oportet, quod ens contrahatur ad diversa
genera secundum diversum modum praedicandi,
qui consequitur diversum modum essendi; quia
“quoties ens dicitur,” idest quot modis aliquid
praedicatur, “toties esse significatur,” idest tot
modis significatur aliquid esse. Et propter hoc ea
in quae dividitur ens primo, dicuntur esse
praedicamenta, quia distinguuntur secundum
diversum modum praedicandi. Quia igitur eorum
quae praedicantur, quaedam significant quid, idest
substantiam, quaedam quale, quaedam quantum, et
sic de aliis; oportet quod unicuique modo
praedicandi, esse significet idem; ut cum dicitur
He says first therefore that those are said to be
essentially which signify the figures of predication.
For it must be known that being cannot be
contracted to something determinate in the way
that a genus is contracted to species through
differences. For a difference, since it does not
participate the genus, is outside the essence of the
genus. But nothing can be outside the essence of
being [such] that through addition to being it
constitutes a species of being: for what is outside
being is nothing and cannot be a difference.
Wherefore in the third [book of] this [work] the
Philosopher proved that being cannot be a genus.
Whence it is necessary that being is contracted to
diverse genera according to a diverse mode of
predicating, which follow a diverse mode of being;
since “being is said as many ways,” that is
something is predicated in as many modes, “as to
be is signified,” that is as many ways as something
is signified to be. And because of this those
[things] into which being is first divided are said to
be predicaments, since they are distinguished
according to diverse modes of predicating. Since
therefore of those [things] which are predicated,
some signify what, that is substance, some how,
55These remarks are based on In Meta. 5.9 and Wippel 213-15.
Carl: Metaphysics 58
homo est animal, esse significat substantiam. Cum
autem dicitur, homo est albus, significat
qualitatem, et sic de aliis.
some how much, and thus for the others; it is
necessary that for each mode of predicating, to be
signifies the same [i.e., a mode of being]; as when
it is said man is animal, to be signifies substance.
But when it is said, man is white, [to be] signifies
quality, and likewise for the others.
Being must be contracted to the categories according to diverse modes of predicating
because it cannot be so contracted according to some difference added to being taken as a genus.
Being must be contracted in some other way, and here St. Thomas claims that being is contracted
to its modes in a manner that parallels the various possible modes of predicating. I think the
appropriate background for this claim is the distinction between apprehension and judgment and
St. Thomas’s claim, which we examined early in the course, that being is not known simply
through the act of apprehension: we said that knowledge of being depends upon the second
operation of the mind, which is judgment. One’s apprehensive grasp of being is complex, being
expressed by a formula like “what has existence” or “that which is.”
To put it another way, being is not known as a genus is known, through abstraction from its
species. To the degree that there is an apprehensive grasp of being, this grasp depends upon
judgment. Therefore it should be no surprise that being is contracted to its ten modes, not by
differences, but according to ten different modes of predicating—that is, ten different modes of
judgment. Just as the signification of the term being depends upon what is grasped by judgment
(being is “that which is,”) so too does the signification of each of the ten categories, taken as ten
modes of being, depend upon the modes according to which one can predicate something. Hence,
substance signifies a mode of being according to the meaning of the verb “to be” in a predication
expressing what something is; whereas quality signifies a mode of being according to the meaning
of the verb “to be” in a predication expressing how something is, etc.
7.3. Other Points Concerning Substance and Accident
Due to the constraints of time, we can only briefly summarize a number of other points to
be made concerning substance and accident and the relationship between them.
The definitions of substance and accident
As Msgr. Wippel notes (pp. 228-237), on a number of occasions St. Thomas stresses that
“being in itself (per se)” is not the definition of substance. When he does comment in a positive
way about the definition of substance, St. Thomas offers the following: “the definition or quasidefinition of substance is a thing having quiddity, to which it is given or belongs to exist not in
something else.”56 The negative character of this definition should be noted, as well as the
inclusion of the reference to having quiddity and St. Thomas’s careful avoidance of defining
substance as something differentiated from being taken as a genus.
As for the definition of accident, in a similar manner St. Thomas qualifies that “being in a
subject” is not the definition of accident; rather, accident is “a thing to which it belongs to be in
56In Sent. 4.12.1.1 ql. 1 ad 2 [Moos 499]: “Sed definitio vel quasi definitio substantiae est res habens
quidditatem, cui acquiritur esse vel debetur non in alio.” The translation is from Wippel 231.
Carl: Metaphysics 59
something else.”57 Consequently St. Thomas frequently characterizes the mode of being
appropriate to accident as “being in” (inesse).58
Accidents and accidental being (esse)
Two related questions have long been discussed among the Thomistic commentators
concerning accidents and being (esse): (1) Does St. Thomas recognize a distinction between a
substance’s act of being (esse) and the acts of being of accidents? (2) Is there a real distinction
between or composition of an accidental form and accidental esse?
Concerning the first, although there have been dissenting voices among the Thomistic
commentators, the majority view and the view clearly supported by the texts of St. Thomas is that
there is a distinction between a substance’s act of being (that is, the act of being that actualizes its
essence) and the act of being (esse) of an accident. St. Thomas characterizes the being caused by
an accident as “a certain secondary being,” which we should understand as a further actualization
of the substance beyond its actuality according to its essence and substantial act of being.
However, whether one should posit a real distinction between an accidental form and the
accidental esse that modifies the subject of the accident is a more difficult question. As Msgr.
Wippel details, at least at some point earlier in his career, St. Thomas does seem to recognize such
a distinction. However, this distinction disappears from his later writings, and as we have seen
above in the so-called “genus” argument for essence-esse composition, St. Thomas argued that
whereas the composition of form and esse in the genus of substance is a real composition, by
contrast the distinction between an accidental form and its esse is only a logical distinction.59
The causal relationship between substance and accident
In general, St. Thomas characterizes the causal relationship between substance and
accident as a case of subject (or quasi-material) causality on the part of substance, and formal
causality on the part of accident. That is, an accident is a form that exists in a substance insofar as
it is a further actualization of the substance in some definite way: for example, Socrates’ being here
or Socrates’ being wise.
However, the class of accidents typically called properties (or proper accidents) must also
be characterized as caused by or flowing from the substance according to its essence. We will
quickly examine one text that draws the relevant distinctions in this regard, Quaestiones disputatae
De anima, q. 12, ad 7:
Ad septimum dicendum quod tria sunt genera
accidentium: quedam enim causantur ex
principiis speciei et dicuntur propria, sicut
risibile homini; quedam causantur ex
principiis indiuidui, et hoc dupliciter: quia uel
To the seventh objection [it is said] that there are
three kinds of accidents: for some are caused by
the principles of the species and are called proper
[accidents], such as risible of man; others are
caused by the principle of the individual, and this
in two ways: since they either have a permanent
57Ibid.: “Et similiter esse in subiecto non est definitio accidentis, sed e contrario res cui debetur esse in alio.”
The translation is from Wippel 234.
58Wippel 235.
59See Wippel 265 for summary comments about this issue.
Carl: Metaphysics 60
habent causam permanentem in subiecto, et
hec sunt accidentia inseparabilia, sicut
masculinum et femininum et alia huiusmodi;
quedam uero habent causam non semper
permanentem in subiecto, et hec sunt
accidentia separabilia, ut sedere et ambulare.
Est autem commune omni accidenti quod non
sit de essentia rei; et ita non cadit in
diffinitione rei. Vnde de re intelligimus quid
est absque hoc quod intelligamus aliquid
accidentium eius. Set species non potest
intelligi esse sine accidentibus que
consequuntur principium speciei; potest tamen
intelligi esse sine accidentibus indiuidui, etiam
inseparabilibus. Sine separabilibus uero
esse potest non solum species, set etiam
indiuiduum.
cause in the subject, and these are inseparable
accidents, such as masculine and feminine and
others of this kind; but others have a cause not
permanent in the subject, and these are separable
accidents, such as to see and to walk. But it is
common to every accident that it not be of the
essence of the thing; and thus it does not fall under
the definition of the thing. Wherefore we
understand of a thing what it is without this, that
we should understand something of its accidents.
But a species cannot be understood to exist without
the accidents which follow upon the principle of
the species; nevertheless it can be understood to
exist without the accidents of an individual, even
the inseparable [accidents]. But not only the
species, but even the individual, can exist without
the separable [accidents].
Here St. Thomas distinguishes among three kinds of accidents:
(1) Properties or proper accidents: these accidents follow from the essential character of
the species. For example, risibility follows upon rationality in man. While the substance, man, is
the subject of risibility, it must also be said that the essence of the substance is the formal cause of
risibility. This sort of causal relationship between the essence of a substance and its properties is at
issue in demonstration propter quid.
(2) Inseparable accidents: there are some accidental features of a thing that follow upon
some intrinsic cause that exists permanently, i.e., as long as the substance exists. For example, that
a human being is male or female is an inseparable accident. It does not belong to the species as a
property for a human being to be either male or female; instead it follows from what St. Thomas
here calls the principle of the individual, i.e., the substance’s material cause. Thus, while the
substance is the subject of an inseparable accident, one can also recognize the substance’s matter as
a cause of an inseparable accident.
(3) Separable accidents: these are accidents as we most commonly speak about them, the
changeable features of a given substance. That one is here now, there at another time; that one is
seeing now, but not at another time, etc. Typically when we speak of substance-accident
composition, we are speaking of separable accidents; and separable accidents are forms that further
actualize a given substance in a particular way.
Now, St. Thomas notes that it is common to every kind of accident that an accident does
Carl: Metaphysics 61
not belong to the essence (or consequently to the definition) of the thing.60 However, this does not
mean that a substance can exist without any of these kinds of accidents. St. Thomas clarifies that it
is impossible to conceive of the existence of a given species without its possessing the properties
or proper accidents that follow upon the essence of the species. Even though these properties do
not belong to one’s knowledge of what the species is, nevertheless one cannot think of the species
as existing without its properties.
By contrast, one can think of a species as existing without the other accidents, both
inseparable and separable. St. Thomas does not mean that one can conceive of an individual
without inseparable accidents; rather, he means that the species can exist without the inseparable
accidents, because it is possible for the species to be instantiated in an individual without a given
inseparable accident. However, the individual cannot exist without its inseparable accidents.
Finally, St. Thomas notes that both the species and the individual can exist without the
separable accidents: this follows from their being separable.
60It is in this sense that he will also say, in other contexts, that a thing’s act of being (esse) is accidental to
it—even though, strictly speaking, esse cannot be construed as an accident, because accidents actualize
substances beyond their substantial acts of being.
Carl: Metaphysics 62
8. Matter-form Composition in Corporeal Substances
Having considered the ways in which all beings other than God are composite—that is, by
the composition of essence and esse and the composition of substance and accidentwe now shift
our attention to a consideration of corporeal substances and another mode of composition in them:
the matter-form composition of their essences. We will consider the following questions: (1) How
does one establish the matter-form composition of corporeal substances? (2) What is prime matter,
and what can we say about it? (3) Can there be more than one substantial form in a thing? (4) What
is the principle of individuation in corporeal substances?61
8.1. Establishing the Hylomorphic Composition of Corporeal Substances
Following Aristotle, St. Thomas offers as the primary evidence of the matter-form
composition of corporeal substances the fact of motion or change. It is evident to the senses that
change occurs, i.e., that certain things come to be and pass away. However, change is only
intelligible when one admits the following three principles: (1) the form or characteristic that
comes to exist, (2) the privation of this form prior to the change, and (3) some subject of the
change that underlies both the privation and the form.62 These are Aristotle’s three principles of
nature: form, privation, and matter. All that is meant by the term matter in this broad sense is the
subject of a change, or that to which a change occurs.
The matter-form composition of corporeal substances is in this way first established
insofar as they are subject to change, and for this reason Msgr. Wippel characterizes this way of
establishing matter-form composition as more proper to physics than to metaphysics.63 Utilizing
this approach, one draws a distinction between two different kinds of change: (1) accidental
change, and (2) substantial change. The former kind of change involves the gain or loss of an
accidental form, without the substance that is the subject of the accident ceasing to exist. In the
latter kind of change, it is a substance that passes away, with another substance coming to be in its
place.
Understanding the term matter to mean just the subject of change, it is clear that the matter
of accidental change and the matter of substantial change will be different from one another. The
subject of an accidental change is just a substance, which is the subject of accidents. But the matter
of a substantial change cannot itself be a substance, because in a substantial change the substance
passes away and a new substance comes to exist in its place. For this reason, the matter that
underlies substantial change is not a substance, but what Aristotle and St. Thomas call prime
matter.
In the Commentary on the Physics, Book I, lec. 13, which concerns Aristotle’s presentation
of the three principles of nature, St. Thomas comments as follows:
Et dicit quod natura quae primo subiicitur And he says that the nature which is first subjected
61The presentation of these four topics closely tracks the organization of c. 9 of Msgr. Wippel’s The
Metaphysical Thought of Thomas Aquinas.
62See Physics 1.7.
63This should not present any special difficulty, as it will still pertain to metaphysics to clarify the
relationship between substantial form and prime matter, as principles, to the other principles of
composition distinguished in metaphysics. As we shall see, St. Thomas also characterizes the argument
for prime matter’s being a principle of pure potency distinct from all forms as pertaining to metaphysics
rather than physics.
Carl: Metaphysics 63
mutationi, idest materia prima, non potest sciri per
seipsam, cum omne quod cognoscitur, cognoscatur
per suam formam; materia autem prima
consideratur subiecta omni formae. Sed
scitur secundum analogiam, idest secundum
proportionem. Sic enim cognoscimus quod lignum
est aliquid praeter formam scamni et lecti, quia
quandoque est sub una forma, quandoque sub alia.
Cum igitur videamus hoc quod est aer quandoque
fieri aquam, oportet dicere quod aliquid existens
sub forma aeris, quandoque sit sub forma aquae: et
sic illud est aliquid praeter formam aquae et
praeter formam aeris, sicut lignum est aliquid
praeter formam scamni et praeter formam lecti.
Quod igitur sic se habet ad ipsas substantias
naturales, sicut se habet aes ad statuam et lignum
ad lectum, et quodlibet materiale et informe ad
formam, hoc dicimus esse materiam primam. Hoc
igitur est unum principium naturae: quod non sic
unum est sicut hoc aliquid, hoc est sicut aliquod
individuum demonstratum, ita quod habeat
formam et unitatem in actu; sed dicitur ens et
unum inquantum est in potentia ad formam.
to change, which is prime matter, cannot be known
in itself, since everything that is known, is known
through its form; but prime matter is considered [to
be] the subject of every form. But it is known
according to analogy, that is, according to
proportion. For thus we know that wood is
something other than the form of a bench and of a
bed, since at one time it is under the one form, at
another time under the other. When therefore we
see this which is air sometimes to become water, it
is necessary to say that something existing under
the form of air, at another time be under the form
of water: and so that is something besides the form
of water and besides the form of air, as the wood is
something besides the form of a bench and the
form of a bed. Therefore this [matter] is related to
the natural substances just as bronze is related to
the statue and wood to the bed, and everything
material and unformed to form; this we say to be
prime matter. Therefore this is one principle of
nature: which is not one as a this-something, that is
as some determinate individual, as though it had
form and unity in act; but it is called a being and
one insofar as it is in potency to form.
Following Aristotle, St. Thomas argues for prime matter by an analogy of
proportion(ality):
WOOD : BENCH & BED : : PRIME MATTER : AIR & WATER
This argument for recognizing prime matter is therefore based upon the recognition of a
kind of change that is not merely accidental, but is a change in the very kind of substance. Prime
matter is to be recognized not as a “this-something” (that is, as a concrete being or a supposit), but
rather as a principle of potency relative to the form of a substance. Prime matter is never known in
itself, and as we will clarify in a moment, it never exists independently of substance: it is just that
which underlies substantial change and therefore functions as the subject of substantial form.
In the Commentary on the Metaphysics, Book VII, lec. 2 (#1285 – 1289), St. Thomas takes
up the issue of prime matter from a more metaphysical perspective. In this place, St. Thomas
argues that it pertains more to natural philosophy than to metaphysics to distinguish prime matter
Carl: Metaphysics 64
as the underlying subject of change. He observes that in Book VII, c. 3 of the Metaphysics,
Aristotle establishes the claim that prime matter differs from all forms by using “the method of
predication, which is proper to dialectics and is closely connected with this science.”
In brief, the argument that St. Thomas presents is that one must identify something as the
ultimate subject of which all terms are predicated; not in the sense of univocal predication, but in
the sense of denominative predication, in which the subject and the predicate differ essentially or
in genus. That is, denominative predication is the mode of predication according to which
accidents are predicated of substance (or in general, the mode in which a term from a genus is
predicated of something from outside of that genus). For example:
Man is animal. -univocal or essential predication (man and animal are the same in
genus)
consequence: “Humanity is animality” is also true.
Man is white. -denominative predication (man and white differ in genus)
however: “Man is whiteness” is false, and “Humanity is whiteness” is false.
Now, employing the distinction between univocal or essential predication and
denominative predication, St. Thomas argues that “actual substance is not predicated of matter
univocally or essentially, but denominatively.” As evidence of this, he notes:
This material thing (materiatum) is man. -true
Matter is man. -false
Matter is humanity. -false
Substance is therefore predicated denominatively of matter, just as accidents are predicated
denominatively of substance; and therefore matter does not belong to the genus of substance, and
consequently matter must differ essentially from every substantial form.
8.2. An Examination of Prime Matter as Pure Potentiality
The central claim made by St. Thomas concerning prime matter is that, as a principle of
potency for receiving substantial form and insofar as it is distinct from every form or principle of
actuality, prime matter in itself must be pure potentiality. Prime matter possesses no characteristics
apart from the very potency for receiving substantial form, and in itself it is in potency to receive
any substantial form.64 St. Thomas reaffirms this view frequently throughout his career, asserting
that prime matter is distinct from every form and therefore possesses no positive characteristics of
any kind: it is just the principle of potency for receiving substantial form.
That prime matter should be understood as a principle of pure potency was a controversial
position in the 13th and 14th centuries; it was a common view particularly among the Franciscans
that prime matter must itself possess some degree of actuality apart from its being informed by any
substantial form. As we shall see, as a consequence the thesis that prime matter is pure potency is
closely connected with the thesis that there is only one substantial form in a given substance.
St. Thomas’s arguments for the claim that prime matter is pure potency fall under two
headings: in both cases, his primary concern is typically to defend one of two related claims. The
first related claim is the one we have already examined, which is that matter as such is to be
64One can draw a parallel between prime matter as pure potency and the potential intellect as possessing the
capacity to receive the intelligible likeness of anything that it can know.
Carl: Metaphysics 65
distinguished from any form. The second related claim, as just noted, is the thesis that there is only
one substantial form in any corporeal substance: we will address this claim in the next section of
the course notes. Our concern in this section, therefore, will primarily be just to clarify St.
Thomas’s claim that prime matter is pure potency.
One can find a very large number of texts in which St. Thomas expresses his position that
prime matter is pure potency. For example, In Sent. 1.39.2.2 ad 4:
[A]liquid enim est quod habet esse tantum in
potentia sicut materia prima, et hoc semper habet
defectum, nisi removeatur per aliquod agens
reducens eam in actum.
For there is something which has being (esse) only
in potency, such as prime matter, and this always
has a defect, unless it be removed through some
agent reducing it to act.
In this text, and in others, St. Thomas compares prime matter as pure potency to God as
pure act. In the hierarchy or gradation of being, prime matter is as it were at the opposite extreme
compared to God, with all the beings that involve an admixture of act and potency in between.
In another text, SCG 1.17, St. Thomas argues for the conclusion that there is no matter in
God. In this place he touches on a curious theory advanced by one medieval thinker:
In hoc autem insania David de Dinando
confunditur, qui ausus est dicere Deum esse idem
quod prima materia, ex hoc quod, si non esset
idem, oporteret differre ea aliquibus differentiis, et
sic non essent simplicia; nam in eo quod per
differentiam ab alio differt, ipsa differentia
compositionem facit.
Hoc autem processit ex ignorantia qua nescivit
quid inter differentiam et diversitatem intersit.
Differens enim, ut in X Metaph. determinatur,
dicitur ad aliquid, nam omne differens aliquo est
differens: diversum autem aliquid absolute dicitur,
ex hoc quod non est idem. Differentia igitur in his
quaerenda est quae in aliquo conveniunt: oportet
enim aliquid in eis assignari secundum quod
differant; sicut duae species conveniunt in genere,
unde oportet quod differentiis distinguantur. In his
autem quae in nullo conveniunt, non est
quaerendum quo differant, sed seipsis diversa sunt.
But on this [issue] the madness of David of Dinant
is confounded, who dared to say that God is the
same as prime matter, from this that, if He were
not the same, He would have to differ from it by
some differences, and thus they would not be
simple; for in that which differs from another
through a difference, that difference forms a
composition [with it].
But this [view] proceeds out of ignorance, in that
he did not know what distinguishes difference and
diversity. For the different, as in Metaphysics X, is
said with respect to something, for every difference
is different by something: but something is called
diverse absolutely, from this that it is not the same.
Therefore difference must be sought among those
that agree in something: for it is necessary that
something in them be designated according to
which they differ; as two species share in a genus,
whence it is necessary that they be distinguished
by differences. But among those which share in
Carl: Metaphysics 66
Sic enim et oppositae differentiae ab invicem
distinguuntur: non enim participant genus quasi
partem suae essentiae: et ideo non est quaerendum
quibus differant, seipsis enim diversa sunt. Sic
etiam Deus et materia prima distinguuntur, quorum
unus est actus purus, aliud potentia pura, in nullo
convenientiam habentes.
nothing, that by which they differ is not to be
sought; rather, they are diverse in themselves. For
in this way too opposite difference are
distinguished from one another: for they do not
participate a genus as a part of their essence: and
therefore those things by which they differ are not
to be sought, for they are diverse in themselves. In
this way too God and prime matter are
distinguished, of which one is pure act, the other
pure potency, having agreement in nothing.
Prime matter as pure potency is distinguished from God as pure act not by any difference,
but rather by an absolute diversity. We have already seen Thomas suggest a similar kind of
distinction by absolute diversity between God as ipsum esse per se subsistens and creatures as
instances of participated esse.
What, then, should we say that prime matter is? It is nothing but the potency for substantial
form (and to be precise, for the substantial form of corporeal substances). In any corporeal
substance, St. Thomas contends that we should distinguish between that thing’s substantial form as
the cause that makes the thing to be what it is and its prime matter, which is the principle in it that
receives and limits the substantial form. We will have more to say on this point in consideration of
matter as the principle of individuation.
Prime matter cannot exist independently
As a consequence of prime matter’s being pure potentiality with no formal characteristics,
it should not be a surprise that St. Thomas holds that prime matter cannot exist apart from
composition with a substantial form—and not even by the power of God. It is not possible for
prime matter to exist apart from substantial form, because it is substantial form that communicates
existence to prime matter (not as an efficient cause, but as a formal cause). As St. Thomas puts it in
Summa contra Gentiles II c. 43, in responding to the suggestion that God first created prime matter
and then left it to be informed by other agents: “Prime matter could not have existed by itself prior
to every formed body, since it is not anything except pure potency; for every existent in act is from
some form.”
Indeed, St. Thomas holds that to assert that prime matter could exist by itself apart from
any form would be to assert a contradiction: “To say that matter pre-exists without form is to
express being in act without act, which implies contradiction.”65 Not even by the power of God,
therefore, will St. Thomas allow that prime matter could exist without form, because God cannot
do anything that entails a contradiction. He affirms this position explicitly in Quodlibet 3 q. 1 a. 1:
“Existing non-being, at the same time and in the same respect, is repugnant to the character of
being: therefore that something should at the same time both be and not be, cannot be done by
God, nor something including a contradiction. But for matter to be in act without form is of this
65Summa theologiae I q. 66 a. 1: “Dicere igitur materiam praecedere sine forma, est dicere ens actu sine
actu,: quod implicat contradictionem.”
Carl: Metaphysics 67
kind [i.e., it implies a contradiction].”66
Thus, although St. Thomas recognizes a real distinction and composition between
substantial form and prime matter, this does not imply that prime matter is capable of existing
independently from substantial form. This is a crucially important point for our understanding of
what St. Thomas means by a real distinction: it does not imply the possible separate and
independent existence of the items distinguished. In this, St. Thomas’s position differs from that of
many other medieval theologians and philosophers, who do take real distinction to imply the
possibility of independent existence.
8.3. The Unicity of Substantial Form in Corporeal Substances
The third point that we should address is St. Thomas’s thesis that in a given corporeal
substance there is only one substantial form. This issue is closely connected to the question of
whether or not in man there is only one soul. This latter question was so controversial in the late
13th and early 14th centuries that the remarkable study, Early Thomistic School (by Frederick
Roensch, 1964), distinguishes between followers of St. Thomas and his philosophical opponents
just by the criterion or acceptance or disagreement with this thesis of the unicity of soul or
substantial form.
In brief, the position favored by most Franciscan and secular theologians was that in a
given corporeal substance (and in particular in a human being), there is more than one substantial
form, each one corresponding to a different degree of organization and actuality in the substance.
For example, such a view might posit that in a man there is a substantial form according to which a
man is corporeal, another according to which he is living (a vegetative soul), another according to
which he has sensation (a sensitive soul), and another according to which he is rational (a rational
soul). On this view, the rational soul is only the last of these substantial forms, and one can accept
both that there are multiple substantial forms and even multiple souls in a single individual human
being.
Against such a view, St. Thomas argues that substantial form is what makes a thing to be
what it is, giving it its unity and identity as an instance of a given essential kind. If, therefore, there
were several substantial forms (including souls) in a given substance, that substance would not
truly be one thing of one kind with substantial unity: the unity and identity of a substance depends
upon the unicity of its substantial form.
We can turn to two of the arguments from one of St. Thomas’s extended treatments of the
issue of the unicity of soul in man; but we should note that his reasoning can be extended to the
issue of unicity of substantial form in any substance. This text is SCG 2.58:
Quae attribuuntur alicui eidem secundum diversas
formas, praedicantur de invicem per accidens:
album enim dicitur esse musicum per accidens,
quia Socrati accidit albedo et musica. Si igitur
anima intellectiva, sensitiva et nutritiva sunt
Those which are attributed to the same thing
according to diverse forms, are predicated of one
another per accidens: for white is said to be
musical per accidens, since whiteness and musical
are accidental to Socrates. If therefore the
66Quodlibet 3 q. 1 a. 1: “Repugnat autem rationi entis non ens, simul et secundum idem, existens: unde quod
aliquid simul sit et non sit, a Deo fieri non potest, nec aliquid contradictionem includens. Et de huiusmodi
est materiam esse actu sine forma. . .” See Wippel 324-25.
Carl: Metaphysics 68
diversae virtutes aut formae in nobis, ea quae
secundum has formas nobis conveniunt, de
invicem praedicabuntur per accidens. Sed
secundum animam intellectivam dicimur homines,
secundum sensitivam animalia, secundum
nutritivam viventia. Erit igitur haec praedicatio per
accidens, homo est animal; vel, animal est vivum.
Est autem per se: nam homo secundum quod est
homo, animal est; et animal secundum quod est
animal, vivum est. Est igitur aliquis ab eodem
principio homo, animal et vivum. . . .
intellective, sensitive, and nutritive souls are
diverse powers or forms in us, then those things
which belong to us according to these forms,
would be predicated of one another per accidens.
But according to the intellective soul we are called
men, according to the sensitive [soul we are called]
animals, according to the nutritive [soul we are
called] living. Therefore this predication will be
per accidens: man is animal; or, animal is living.
But this predication is per se: for man insofar as he
is man, is animal; and animal insofar as it is
animal, is living. Therefore it is by the same
principle that one is a man, an animal, and
living. . . .
The essential (per se) predication of all of the parts of the definition of a substance can
only be preserved, on St. Thomas’s view, by the unicity of soul in man (or the unicity of substantial
form in general). Otherwise, what belongs to a thing according to one of its substantial forms
would be accidental to what it is according to another of its substantial forms, with the absurd
consequence that it would be accidental to a man that he be an animal.
Praeterea. Ab eodem aliquid habet esse et
unitatem: unum enim consequitur ad ens. Cum
igitur a forma unaquaeque res habeat esse, a forma
etiam habebit unitatem. Si igitur ponantur in
homine plures animae sicut diversae formae, homo
non erit unum ens, sed plura. Nec ad unitatem
hominis ordo formarum sufficiet. Quia esse unum
secundum ordinem non est esse unum simpliciter:
cum unitas ordinis sit minima unitatum.
Furthermore. Something has being (esse) and unity
from the same [principle]: for one follows upon
being (ens). Since therefore each thing has being
(esse) from form, it will also have unity from form.
If therefore there be posited in man several souls as
diverse forms, man will not be one being, but
several. Nor will an order of forms suffice for the
unity of a man, because to be (esse) one according
to order is not to be (esse) one simply: since unity
of order is the least of unities.
That unity follows upon being is a claim that we will investigate later, in our consideration
of the transcendentals. This is a claim that St. Thomas appropriates from Aristotle: insofar as
something is a being, it is one. Since substance is being in the primary and simple sense, it must be
the case that a substance is one. Now, the substantial form is the cause that makes the substance to
be what it is, and for this reason St. Thomas says that it is from the form that each thing has esse. If
therefore there were several substantial forms (or souls) in a thing, then that thing would not be one
thing, but several.
Carl: Metaphysics 69
St. Thomas also excludes the suggestion that a plurality of substantial forms could make a
thing to be one through a unity of order. A unity of order is the way in which, for example, the
members of an army or students in a class are one. If there were a unity of order among some
group of substances simply according to their substantial forms, one would have many substances
unified by order, and not one substance simply.
For St. Thomas, the unicity of substantial form in every substance is a general
metaphysical thesis; it is not a claim restricted to the issue of the soul. A thing must have one
substantial form in order to be one substance.
The problem of proximate matter and the mixture of the elements
Although St. Thomas holds strictly to the thesis that there is only one substantial form in a
given substance, nevertheless he also holds to such claims as the following:
(1) The particular matter out of which a given substance is generated can have an effect on
the characteristics of the resulting substance. That is, one substance can have different qualities
from another substance that can only be accounted for in differences in their matter that in a way
pre-existed the substances themselves.
(2) In general, St. Thomas allows that one can account for the characteristics of certain
substances (such as living things) from their being composed from contraries, i.e., from the
elements, which are themselves distinguished by their contrary qualities. For example, St. Thomas
repeatedly claims that living things are corruptible and mortal because they are composed from the
elements.
Now, if substantial change has prime matter as a subject, and if prime matter has of itself
no positive characteristics, then it seems impossible that any of the characteristics of the matter
from which a substance comes to be should make any difference in the characteristics of the
resulting substance. Even in general, to claim that any substance that results from the mixture of
the elements will be naturally subject to corruption seems odd, if the substantial forms of the
elements themselves do not remain in the resulting substance.
St. Thomas presents his solution to these solutions in the brief work De mixtione
elementorum, which was composed as a letter responding to an inquiry made to St. Thomas by
Phillip de Castro Caeli, a professor of medicine. In the medical theory of the time, the theory of the
four humors was understood to be based upon the theory of the four elements: each of the bodily
humors corresponded to one of the four elements. Apparently aware of St. Thomas’s position about
the unicity of substantial form, Phillip asked Thomas for clarification about the way in which it can
be said that the elements remain in the substances composed from them.
In his reply, St. Thomas excludes the possibility that in any way the substantial forms of
the elements should remain in any resulting mixed substance composed from the elements,
offering the same sorts of reasons we have already encountered. He criticizes other proposals for
how to solve the dilemma, and finally he presents his own solution towards the end of the work.
That St. Thomas shares Phillip’s concern (that somehow the elements must be preserved in a mixed
body in order for it to even make sense to say that the resulting substance is a mixed body) is
indicated by his introduction to his own solution:
Oportet igitur alium modum invenire, quo et
veritas mixtionis salvetur, et tamen elementa non
It is necessary therefore to find another way in
which both the truth of mixtures be preserved, and
Carl: Metaphysics 70
totaliter corrumpantur, sed aliqualiter in mixto
remaneant.
nevertheless the elements are not entirely
corrupted, but somehow remain in the mixture.
St. Thomas proceeds to note that the qualities of the elements are distinct from the
elemental bodies themselves, and insofar as the elements act upon one another, a given elemental
body can have more or less of its characteristic qualities. There can therefore result from the
accidental mixture of the elements bodies with qualities that are a medium, relative to the qualities
characteristic of the elements themselves.
Now, following Aristotle, St. Thomas contends that alterations—qualitative changes—are
dispositive to substantial changes. The only sense in which substantial change is a process is
insofar as certain qualitative changes precede the moment of substantial change (but a substantial
change in itself occurs in an instant). It is insofar as a body possesses certain qualities that it is
capable of receiving a given substantial form.
Concerning the mixture of the elements, therefore, St. Thomas argues that by their
(initially accidental) mixture, the elements produce mixed bodies with qualities that are dispositive
to the reception of a given substantial form. At the moment of substantial change, it is the prime
matter of the elements that is the true subject of the change. Nevertheless, the qualities that were
preparatory in the body for the reception of the substantial form remain in the new substance, just
insofar as these qualities are the proper qualities of the new substance. The new substance is what
it is by virtue of its substantial form, but there remain in it the qualities that were dispositive to the
reception of that substantial form: and these qualities are now proper qualities in the new substance
as their subject. Since they are qualities of the new substance, they receive their being from the
substance.
As regards the elements in particular, therefore, St. Thomas contends that the elements
remain not actually but virtually in the substances that come to be from the mixture of the
elements. That is, in a given mixed substance, there is no earth, air, fire, or water actually: but the
elements remain insofar as their characteristic powers (which are their qualities) remain in the
mixed body as qualities of the new substance.
This account allows for the possibility of variation in the matter out of which a given
substance comes to exist, with a consequence on the particular characteristics of the resulting
substance. This can occur insofar as the qualities dispositive to the reception of a given substantial
form will admit of a range of possibilities.
8.4. The Principle of Individuation
A famous question for medieval philosophers and theologians concerned the principle
according to which members of a species differ numerically from one another. It was generally
accepted, from the background provided by Porphyry’s Isagoge, that what distinguishes something
specifically from other members of its genus is the specific difference. However, while it was taken
for granted that members of a species differ only numerically, there was some measure of dispute
about the principle that serves to set apart one individual from another member of the same
species.
Designated matter as the principle of individuation
The background for the claim that matter is the principle of individuation is found in two
passages from Aristotle’s Metaphysics.
Carl: Metaphysics 71
(1) The first text comes from Metaphysics 5.6 1016b31-32, which begins with a distinction
among kinds of unity:
In this text, Aristotle points to unity of matter as what accounts for the numerical unity of
an individual: by contrast, unity of intelligible structure is what accounts for specific unity among
two or more individuals.
In commenting on this text (lec. 8), St. Thomas writes as follows:
Ponit aliam divisionem unius, quae est magis
logica; dicens, quod quaedam sunt unum numero,
quaedam specie, quaedam genere, quaedam
analogia. Numero quidem sunt unum, quorum
materia est una. Materia enim, secundum quod stat
sub dimensionibus signatis, est principium
individuationis formae. Et propter hoc ex materia
habet singulare quod sit unum numero ab aliis
divisum. Specie autem dicuntur unum, quorum una
est ratio, idest definitio. Nam nihil proprie
definitur nisi species, cum omnis definitio ex
genere et differentia constet. Et si aliquod genus
definitur, hoc est inquantum est species.
He offers another division of one, [a division] that
is more logical [in character]; saying, that some
things are one in number, others in species, others
in genus, others by analogy. Indeed those are one
in number of which the matter is one. For matter,
insofar as it stands under designated dimensions, is
the principle of the individuation of form. And
because of this a singular thing has that it is one
and divided from others from matter. But those are
called one in species, of which there is one ratio,
that is the definition. For nothing is properly
defined except a species, since every definition is
composed from genus and difference. And if some
genus is defined, this is insofar as it is a species.
St. Thomas interprets this text from the Metaphysics as supporting the claim that it is the
matter of a thing that ultimately accounts for the individuation of form. We will comment below on
the significance of the qualification “insofar as it stands under designated dimensions.”
(2) The second text is Metaphysics 7.8 1033b29-1034a8. In this text, Aristotle is arguing
against the need to posit separate Forms as exemplars or principles of generation:
Further, some things are one in number, some in species, some in genus, and some analogically or
proportionally. Those things are one in number which have one matter; in species, which have one
intelligible structure; in genus, which have the same figure of predication; and proportionally,
which are related to each other as some third thing is to a fourth.
Carl: Metaphysics 72
Aristotle contends that one does not need to posit a separate Form to account for the
generation of a given member of a species; rather, an individual animal is sufficient as a principle
of generation for another animal of the same species. It is not the form as such that is generated,
but rather than individual, which is a form in matter, that is, the composite of form and matter.
St. Thomas comments on the latter portion of this text (lec. 7):
“Omnis autem species, quae est in materia,”
scilicet in his carnibus et in his ossibus, est aliquod
singulare, ut Callias et Socrates. Et ista etiam
species causans similitudinem speciei in generando
est diversa a specie generati secundum numerum
propter diversam materiam. Cuius diversitas est
principium diversitatis individuorum in eadem
specie. Diversa namque est materia, in qua est
forma hominis generantis et hominis generati. Sed
utraque forma est idem secundum speciem. Nam
“But every species, which is in matter,” namely in
this flesh and in these bones, is something singular,
such as Callias or Socrates. And so too this
form/species causing a likeness in species by
generating is diverse in according to number from
the species of the generator, because of diverse
matter. The diversity [of matter] is the principle of
the diversity of individuals in the same species. For
diverse is the matter in which is [found] the form
of the man generating and the form of the man
And in some cases, it is evident that the thing which generates is of the same kind as the thing
which is generated, although they are not the same numerically but specifically, for example, in the
case of natural generations (for man begets man), unless something contrary to nature is generated,
as when a horse begets a mule. And even these cases are alike; for what is common to both horse
and ass as their proximate genus has no name, but perhaps both might be something like mule.
Hence there is evidently no need to furnish a Form as an exemplar; for men would have searched
for Forms especially in sensible things, since these are substances in the highest degree. But the
thing which generates is adequate for producing the thing and for causing the form in the matter.
And when the whole is such and such a form in this flesh and these bones, this is Callias or
Socrates; and they differ in their matter (for the matter of each is different) but are the same in
form, because form is indivisible.
Carl: Metaphysics 73
ipsa species est “individua,” idest non
diversificatur in generante et generato. Relinquitur
ergo, quod non oportet ponere aliquam speciem
praeter singularia, quae sit causa speciei in
generatis, ut Platonici ponebant.
generated. But each form is the same according to
species. For the form/species itself is “indivisible,”
that is, it is not diversified in the one who
generates and the one generated. It follows
therefore that it is not necessary to posit some
Form/species apart from singulars, which is the
cause of the form/species in [things] generated, as
the Platonists claimed.
The species of Socrates and the species of Callias taken as such do not differ: the species is
what is understood to be the same in both Socrates and Callias. However, the form of Socrates
does differ from the form of Callias, insofar as Socrates has this form and Callias has that form,
even if those forms are the same according to species. It is the matter of each that accounts for the
diversification of form. Socrates and Callias differ insofar as this matter is in Socrates, while that
matter is in Callias.
It is helpful to emphasize precisely what is at issue when it is said that designated matter is
the principle of individuation. Matter is said to individuate insofar as it serves to distinguish the
individual from other members of the species. But for St. Thomas (but perhaps not for Aristotle
himself), matter taken universally or abstractly is included in a thing’s essence: that is, the species
(which is what is defined) includes in its definition matter taken universally. Therefore, it is not
matter taken abstractly that is the principle of individuation: it is designated matter, which is to say
this matter as opposed to that matter. It is in this way that St. Thomas consistently contends that
designated matter is the principle of individuation.
Matter under determinate dimensions vs. matter under indeterminate dimensions
Having considered what St. Thomas consistently says throughout his career—that
designated matter is the principle of individuation—we can now turn to a brief consideration of a
more particular issue that St. Thomas seems to have re-thought a number of times during his
career. We can understand the question at issue in this way: what beyond matter taken in itself
(which is to say, matter taken universally or abstractly) suffices to individuate form? That is, what
is it that distinguishes designated matter from undesignated matter? We will consider two
representative texts and then explain what is at issue in this question.
We can take as representative of the view that designated matter is matter under
determinate dimensions St. Thomas’s comments in De ente et essentia c. 2:
Sed quia individuationis principium materia est, ex
hoc forte videretur sequi quod essentia, que
materiam in se complectitur simul et formam, sit
tantum particularis et non universalis: ex quod
sequeretur quod universalia diffinitionem non
haberent, si essentia est id quod per diffinitionem
significatur. Et ideo secundum est quod materia
But since the principle of individual is matter, from
this indeed it would seem to follow that the
essence, which includes in itself both matter and
form, is only particular and not universal: from
which it would follow that universals would not
have a definition, if the essence is that which is
signified through a definition. And therefore it
Carl: Metaphysics 74
non quolibet modo accepta est individuationis
principium, sed solum materia signata; et dico
materiam signatum que sub determinatis
dimensionibus consideratur. Hec autem materia in
diffinitione que est hominis in quantum est homo
non ponitur, sed poneretur in diffinitione Sortis si
Sortes diffinitionem haberet. In diffinitione autem
hominis ponitur materia non signata: non enim in
diffinitione hominis ponitur hoc os et hec caro, sed
os et caro absolute que sunt materia hominis non
signata.
follows that matter taken in every way is not the
principle of individuation, but only designated
matter; and I call designated matter that which is
considered under determinate dimensions. But this
matter is not put in the definition which is of man
insofar as he is man, but it would be put in the
definition of Socrates if Socrates had a definition.
But in the definition of man is placed undesignated
matter: for this flesh and this bone are not put in
the definition of man, but flesh and bone
[considered] absolutely, which are the
undesignated matter of man.
In this text, we find St. Thomas apparently defining designated matter as matter under
determinate dimensions: that is, matter insofar as it is subject to a precise dimensive (i.e.,
continuous) quantity. That is, here designated matter seems to be understood as “this much matter”
or “matter with these dimensions.”
As representative of the view that the principle of individuation is matter under
indeterminate dimensions, we can take St. Thomas’s comments from In DT 4.2:
Non enim forma individuatur per hoc quod
recipitur in materia, nisi quatenus recipitur in hac
materia distincta et determinata ad hic et nunc.
Materia autem non est divisibilis nisi per
quantitatem. Unde philosophus dicit in I
physicorum quod subtracta quantitate remanebit
substantia indivisibilis. Et ideo materia efficitur
haec et signata, secundum quod subest
dimensionibus.
Dimensiones autem istae possunt dupliciter
considerari. Uno modo secundum earum
terminationem; et dico eas terminari secundum
determinatam mensuram et figuram, et sic ut entia
perfecta collocantur in genere quantitatis. Et sic
non possunt esse principium individuationis; quia
cum talis terminatio dimensionum varietur
frequenter circa individuum, sequeretur quod
For form is not individuated through this that it is
received in matter, except insofar as it is received
in this distinct matter, determined to the here and
now. But matter is not divisible except by quantity.
Whence the Philosopher says in Physics I that
quantity removed, [only] indivisible substance will
remain. And therefore matter is rendered this and
designated, insofar as it is under dimensions. But
those dimensions can be considered in two ways.
In one way, according to their termination: and I
call them terminated according to determinate
measure and figure, and so, as complete beings,
[dimensions] are located in the genus of quantity.
And in this way they cannot be the principle of
individuation; since such termination of
dimensions will vary frequently as regards an
individual, [so that] it would follow that the
Carl: Metaphysics 75
individuum non remaneret semper idem numero.
Alio modo possunt considerari sine ista
determinatione in natura dimensionis tantum,
quamvis numquam sine aliqua determinatione esse
possint, sicut nec natura coloris sine
determinatione albi et nigri; et sic collocantur in
genere quantitatis ut imperfectum. Et ex his
dimensionibus indeterminatis materia efficitur
haec materia signata, et sic individuat formam, et
sic ex materia causatur diversitas secundum
numerum in eadem specie.
individual would not always remain the same in
number. In another way [dimensions] can be
considered without that determination, [and] only
in the nature of dimension, although they can never
exist without some determination, just as the nature
of color [cannot exist] without determination to
white or black; and in this way [dimensions] are
located in the genus of quantity as incomplete. And
by these indeterminate dimensions matter is made
this designated matter, and thus it individuates
form, and thus diversity according to number in the
same species is caused by matter.
It would seem that St. Thomas’s primary concern in drawing the distinction between
determinate dimensions and indeterminate dimensions is answering the objection that if designated
matter is the principle of individuation, then insofar as something’s matter changes quantity, it
would lose its numerical identity with itself over time. By saying that it is matter under
indeterminate dimensions that individuates form, St. Thomas can answer such an objection.
However, as we have seen, in other texts, St. Thomas explicitly says that it is matter under
determinate dimensions that serves as the principle of individuation.
As Msgr. Wippel details, St. Thomas seems to have fluctuated between these two opinions
earlier in his career, before generally abandoning the distinction between determinate dimensions
and indeterminate dimensions; when he says anything explicitly on the point in his later texts, it is
in favor of matter under determinate dimensions—or, as we saw in the text from the Commentary
on the Metaphysics, matter under designated dimensions. It would seem then that the view
expressed in the De ente et essentia c. 2 would seem to have been St. Thomas’s mature view on the
issue.
Carl: Metaphysics 76
9. Comparison and Coordination of the Modes of Composition: Potency and Act
As we have seen, in the thought of St. Thomas we can identify three different modes or
levels of composition in the beings that fall under ens commune, the subject of metaphysics. These
are essence-esse composition, substance-accident composition, and matter-form composition. The
former two modes of composition pertain to all of the beings that fall under ens commune, whereas
the third mode pertains only to corporeal substances.
We have seen a variety of approaches, some depending more on logic and others on
argumentation more proper to natural philosophy, for establishing each of these three modes of
composition. We have spent much time attending to details of St. Thomas’s various arguments for
these conclusions, and we have attended to a number of ancillary issues connected with each of the
modes of composition.
In my view, an appreciation of the role that each of these modes of composition plays in
the metaphysical thought of St. Thomas is not complete without consideration of the ways in
which these modes of composition are connected with one another. Therefore, at this point, we will
take up, at least in brief, the work of comparing and coordinating the three modes of composition.
This will allow us to better understand each of the three modes of composition; it will also allow us
to begin to see how St. Thomas’s metaphysical thought hangs together in a systematic way.
9.1. Essence-esse Composition: Coordination with the other Modes of Composition
To begin, we can focus on the most fundamental mode of composition found in ens: this is
the composition of essence and existence or the act of being. To spell out more explicitly
something we have suggested above, we can note that by this thesis, St. Thomas rules out three
possibilities:
(1) St. Thomas wishes to exclude that a thing’s existence or act of being is just one of the
intelligible notes belonging to its essence. It cannot be that a thing’s existence is one of the parts of
the essence: a thing’s existence is never even in a partial way an answer to the question, “what is
it?,” where the answer to this question is just what we mean by essence. That esse is not a part of
essence is the ultimate reason why esse is known not through apprehension, which regards what a
thing is, but rather through judgment. However, insofar as there are parts of the essences that we
understand, this is grounded in matter-form composition.
(2) St. Thomas also wishes to exclude that a thing’s existence or act of being is an accident
that is added to its substance, understood as the subsisting subject. Such a possibility must be
excluded because a substance must already exist in order to be the subject of any accidents: its very
existence or act of being therefore cannot be just one among its many accidents.
(3) St. Thomas also wishes to exclude that any finite thing’s essence is nothing but
existence or the act of being. In his arguments supporting the thesis that there could only be one
being in which essence and esse are identical, it is this way of approaching essence-esse distinction
that is emphasized.
The first and third of these claims excluded by St. Thomas invite us to offer some
comparison between essence-esse composition and (a) matter-form composition. The second claim
invites comparison with (b) substance-accident composition.
Essence-esse and matter-form composition compared; forma dat esse
Carl: Metaphysics 77
The essences knowable by human beings—that is, the essences of corporeal substances—
are composite, even though a thing’s existence or act of being is not one of the parts of the essence.
Rather, the parts of the definition of the essence are taken from the matter and form of the
substance: in particular, the genus is taken from a thing’s (proximate) matter and the difference is
taken from the substantial form. For example, in the definition of man as rational animal, the genus
animal is taken from what man shares in common materially with other sensitive living things,
while the difference rational is taken from the special character of the human soul, which is the
substantial form of the human being.
As St. Thomas repeatedly emphasizes, the knowledge of what a corporeal thing is includes
the matter of the thing, taken abstractly or universally. For example, knowledge of what a man is
includes a knowledge of flesh and bones (which are, it should be noted, common to man and to
some other animals) taken abstractly or universally. But it is designated matter—this flesh and
these bones—that serves to individuate form and to distinguish the individual numerically from
other members of the species. Form can be taken universally as the essence (the forma totius or
form of the whole), in which case it includes only matter taken abstractly; or form can be taken as
this substance’s form, which is individuated by the matter with which it forms a composite (this is
the forma partis, the substantial form of the individual substance).
Given all of this, the question should arise: what is the relationship between essence-esse
composition and matter-form composition? While these might appear to be two totally unrelated
different aspects according to which a given being (ens) can be analyzed, I would emphasize the
importance of the connection between them. We can address this issue by a brief examination of
the axiom forma dat esse: form gives being.
The general understanding of any formal cause is that it is what makes a thing to be what it
is. One must posit a formal cause, in general, because one recognizes sameness of kind in
numerically distinct individuals. The relationship between form and esse can first be appreciated
just by emphasizing two elements of this description of the formal cause: the formal cause makes a
thing (a) to be (b) what it is.
(a) Matter, taken in itself, does not and cannot exist independently: not even by the power
of God does St. Thomas think it possible for prime matter to exist independently. Matter only
exists insofar as it is informed by substantial form. It is therefore the formal cause that causes
matter to be, to exist. “Form gives being” by giving being to matter. One will find St. Thomas
speaking in this way in a special way about the human soul: he says that the human souls
communicates being (esse) to the body.
(b) In “giving being” to matter, a formal cause always causes being of a specific and
therefore limited kind: what results from matter-form composition is a being that can be placed
under the genus of substance and under a species according to the differentiating characteristic that
it shares in common with other members of its species. By being this kind, the resulting substance
is not of another kind. Accordingly, forma dat esse should be understood in conjunction with the
claim that the substantial form limits and determines the kind of being possessed by the resulting
subject. By actualizing matter, which is a principle of potency, substantial form is the principle that
accounts for the limited, determined way in which the resulting substance exists.
Relative to the act of being or existence (esse), therefore, the substantial form is a limiting
principle. This should be understood as a companion to the claim that in general it is essence that
limits or determines the act of being. In other words, of the parts of a corporeal essence (form and
matter), it is form rather than matter that should be understood as the principle that limits existence
Carl: Metaphysics 78
or the act of being.67
Essence-esse and substance-accident composition
Whereas matter-form composition is found only in corporeal substances, St. Thomas holds
that substance-accident composition is found in all of those beings in which there is a composition
of essence and esse. What, then, is the connection between these two modes of composition? Why
is it that everything in which essence is not identical with esse also admits of a composition of
substance and accident? To address this point, we can consider St. Thomas’s arguments in ST
1.54.1 for the conclusion that in an angel, the act of understanding is distinct from the angel’s
substance.
Respondeo dicendum quod impossibile est quod
actio Angeli, vel cuiuscumque alterius creaturae,
sit eius substantia. Actio enim est proprie actualitas
virtutis; sicut esse est actualitas substantiae vel
essentiae. Impossibile est autem quod aliquid quod
non est purus actus, sed aliquid habet de potentia
admixtum, sit sua actualitas, quia actualitas
potentialitati repugnat. Solus autem Deus est actus
purus. Unde in solo Deo sua substantia est suum
esse et suum agere.
Praeterea, si intelligere Angeli esset sua substantia,
oporteret quod intelligere Angeli esset subsistens.
Intelligere autem subsistens non potest esse nisi
unum; sicut nec aliquod abstractum subsistens.
Unde unius Angeli substantia non distingueretur
neque a substantia Dei, quae est ipsum intelligere
subsistens; neque a substantia alterius Angeli.
Si etiam Angelus ipse esset suum intelligere, non
I respond by saying that it is impossible that the
action of an Angel, or of any other creature
whatsoever, be its substance. For action is the
proper actuality of a power; just as esse is the
actuality of a substance or essence. But it is
impossible that something which is not pure act,
but has something of potency admixed, should be
its actuality, since actuality is opposed to
potentiality. But God alone is pure act. Therefore
in God alone, His substance is His esse and his
action.
Furthermore, if the understanding of an Angel were
its substance, it would be necessary that the
understanding of an Angel be subsistent. But
subsistent understanding cannot be but one; as
neither [is] something abstract subsistent.
Therefore the substance of one Angel would not be
distinguished either from the substance of God,
which is the subsistent understanding itself; nor
from the substance of another Angel.
Also, if an Angel itself were its understanding,
67
On the other hand, relative to the substantial form, designated matter is also a limiting principle. However,
it should not be understood as a principle limiting the act of being itself, but as a principle limiting the
essence taken as universal to this individual. As a consequence, one can affirm that distinct members of a
given species participate in the act of being taken in common (esse commune) to the same degree, even if
one must deny that ens is predicated univocally of these individuals, because the esse of this individual is not
the esse of that individual. As Msgr. Wippel details at the end of c. 9, Fr. Joseph Owens has argued that in the
order of reality, it is ultimately a substance’s esse, which is caused by God, that is the principle of
individuation: here the emphasis is not on individuality as numerical difference from other members of a
species, but on individuality as a thing’s independent existence as such.
Carl: Metaphysics 79
possent esse gradus in intelligendo perfectius et
minus perfecte, cum hoc contingat propter
diversam participationem ipsius intelligere.
there could not be grades in understanding more
and less perfectly, since this occurs on account of
the diverse participation of understanding itself.
Certain aspects of these arguments do presuppose God’s existence as pure act, which we
have not yet considered in this course; and so we will not belabor defense of the argumentation
found here. We only need to highlight that even as regards angels and the acts that they perform
just insofar as they are intelligent substances, St. Thomas denies that there can be an identity
between the activity of understanding and the substance of the angel. That is, substance-accident
composition immediately follows, for St. Thomas, from essence-esse composition.
Carl: Metaphysics 80
9.2. Difference and Identity in Real Composition
At this point, we will conclude our consideration of the modes of composition found in ens
commune by considering two texts that I would argue should guide our understanding of the
meaning of composition in the thought of St. Thomas. The first of these texts distinguishes two of
the modes of composition from the other with respect to the character of the otherness or
difference between the paired principles of composition. The second text will express the identity
of the principles of composition in terms of potency and act.
Difference in the principles of composition
In Quodlibet II q. 2 a. 1, St. Thomas takes up the question of whether angels are composed
in their substance of essence and esse. The first objection is as follows:
Videtur quod angelus non componitur
substantialiter ex essentia et esse. Essentia enim
angeli est ipse angelus, quia quiditas simplicis est
ipsum simplex; si ergo angelus componeretur ex
essentia et esse, componeretur ex se ipso et alio;
hoc autem est inconveniens; non ergo
substantialiter componitur ex essentia et esse.
It seems that an angel is not substantially
composed of essence and existence (esse). For the
essence of an angel is the angel itself, since the
quiddity of [something] simple is itself simple; if
therefore the angel were composed of essence and
existence (esse), it would be composed of itself
and something else; but this is unfitting; therefore
it is not substantially composed from essence and
existence (esse).
This argument rests upon two claims, the first of which we have explicitly encountered
before: (1) the essence of an angel or separate substance is not composed (that is, composed of
matter and form); and (2) in an angel there is no real distinction of essence and supposit. This latter
is a claim that St. Thomas affirms throughout his career; however, in the very next article of this
Quodlibet II q. 2, he carefully distinguishes the sense in which in an angel nature or essence and
supposit can be said to differ.68 We do not need to dwell on this difficult issue at this point, but I
would argue that the text we are considering (Quodlibet II q. 2 a. 1 ad 1) can provide some helpful
insight for reading a. 2.
From these two claims, the first objection concludes that an angel cannot be composed
from essence and esse, because this would be to suggest that it is composed from itself (its
essence) and something else. St. Thomas replies to this objection as follows:
Ad primum ergo dicendum quod aliquando ex hiis
que simul iunguntur relinquitur aliqua res tertia,
sicuti ex anima et corpore constituitur humanitas,
To the first therefore it must be said that sometimes
from these [principles] which are joined together
there results some third thing, just as the humanity
68See Wippel 243-51 for extended discussion of Quod. 2.2.2 and the question of whether or not its doctrine
can be reconciled with St. Thomas’s earlier position. In brief, St. Thomas defends a real distinction of
essence and supposit in every creature (including angels) insofar as every creature as a substance is the
subject of accidents: there are therefore things that every created substance is (according to its accidents)
that are not identical with its essence.
Carl: Metaphysics 81
que est homo, unde homo componitur ex anima et
corpore; aliquando autem ex hiis que simul
iunguntur non resultat res tertia, sed resultat
quedam ratio composita, sicut ratio hominis albi
resolvitur in rationem hominis et in rationem albi,
et in talibus aliquid componitur ex se ipso et alio,
sicut album componitur ex eo quod est album et ex
albedine.
which is a man is constituted from soul and body;
wherefore a man is composed from soul and body.
But sometimes from these [principles] which are
joined together there does not result a third thing,
but there results a certain composite notion (ratio),
just as the notion (ratio) of white man is resolved
into the notion (ratio) of man and the notion (ratio)
of white, and in such [composites] something is
composed from itself and another, just as a white
thing is composed from that which is white and
whiteness.
Here St. Thomas replies to the objection (that angels cannot be composed from essence
and esse because this would be the composition of the angel itself with something else) by arguing
that in the case of substance-accident composition, one does have the composition of something
itself with another: what results from substance-accident composition is not a third thing besides
the substance itself or its accident, but the substance existing in a particular way. St. Thomas thus
calls “white man” a ratio composita (a composite notion), insofar as in the order of reasoning one
resolves “white man” into the notions of “man” (a substance) and “white” (an accident). This is not
to say that substance-accident composition is not a real composition; rather, it is only to deny that
what results from such composition is not a third thing distinct from the substance itself.
St. Thomas holds that the composition of soul and body in man is the composition of two
principles that results in a “third thing” distinct from either the soul or the body taken by
themselves. Socrates is a third thing, relative to his formal cause and his material cause.69 But
white Socrates or ugly Socrates is not a third thing: it is just Socrates existing in a particular way.
So too, in the case of an angel, we can say that the existing angel is not some third thing distinct
both from the angel’s existence and from its essence: rather, it is the angel itself, existing.
Thus, one can say that existence is, as it were, something accidental to essence in finite
beings. St. Thomas draws this conclusion explicitly in the body of Quod. 2.2.1:
Sic ergo in angelo est compositio ex essentia et
esse, non tamen est compositio sicut ex partibus
substantiae, sed sicut ex substantia et eo quod
adheret substantiae.
Therefore there is in an angel composition of
essence and existence (esse); nevertheless, there is
not a composition as from the parts of the
substance, but as from the substance and that
69I have a suspicion that the example of this man being a third thing relative to body and soul may be a
consequence of the peculiar case of the human soul, which is specially created and infused by God, rather
than insofar as this is an example of matter-form composition in general. The next text we will
consider—which concerns the way in which matter and form can be identified—could be seen as
supporting this suspicion. Nevertheless, I present this text from Quod. 2.2.1 ad 1 as Msgr. Wippel
presents it (pp. 103-104), taking the composition of human soul and body as an example of the
composition of form and matter in general.
Carl: Metaphysics 82
which adheres to the substance.
This is not to say that existence is, strictly speaking, an accident. However, the
composition of essence and esse is like substance-accident composition, in that in both cases what
results from the composition is just the substance itself, existing (1) at all (according to its esse)
and (2) in particular ways (according to its accidents).
This text highlights for us what we should not take composition to mean: it does not mean
that the principles from which a thing is composed are themselves things distinct from the
composite. This is the foundation for a claim that we have repeated previously: composition from
principles does not necessarily imply the possibility of separation or independent existence on the
part of the principles.
In the case of essence-esse composition, neither the essence nor the esse of any being (ens)
ever exist independently of one another: indeed, we can see that this would be a contradiction in
terms, to say that something exists without its existence or that its existence exists without that of
which it is the existence.
Identity even in matter-form composition
In the text we have just considered, we have seen a contrast drawn between substanceaccident and essence-esse composition on the one hand and matter-form composition on the
other.70 The real difference between matter and form seems stronger, insofar as what results from
their composition is described as a third thing (tertia res). As a counterweight to this text, we
should consider a remark that St. Thomas offers in In Meta. 8.5:
Sed sicut dictum est, ultima materia, quae scilicet
est appropriata ad formam, et ipsa forma, sunt
idem. Aliud enim eorum est sicut potentia, aliud
sicut actus. Unde simile est quaerere quae est
causa alicuius rei, et quae est causa quod illa res sit
una; quia unumquodque inquantum est, unum est,
et potentia et actus quodammodo unum sunt. Quod
enim est in potentia, fit in actu.
But as has been said, the ultimate matter, which
namely is appropriated to form, and the form itself,
are the same. For one of these is as potency, the
other as act. Wherefore to ask what the cause of
some thing is, is similar [to asking] what is the
cause that makes that thing be one; because each
thing insofar as it is, is one, and potency and act in
a certain respect are one. For what is in potency, is
made [to be] in act.
Matter and form are composed and really distinct, and yet nevertheless one can also affirm
that in this corporeal substance the form is the matter: because form is just the actualization of
matter taken as a principle of potency. What the matter taken in itself is potentially, the form is
actually. Potency and act are correlated therefore in such a way that one should think of act, in
composite things, always as the actualization of potency.
Potency and act
70As noted in the previous footnote, I have some suspicion that perhaps the previous text’s remarks about
matter-form composition might be restricted only to the example offered, i.e., the body-soul composition
of a human being. Nevertheless, in any event the text we will now consider offers an important
counterweight concerning matter-form composition.
Carl: Metaphysics 83
Having considered the three modes of composition found in ens commune, it is necessary
at this point to offer the general observation that in each case, one can compare the two principles
of composition as principles of potency and act, respectively:
Act : Esse Form Accident
______ _______ ______ ________
Potency : Essence Matter Substance
We can offer the following general conclusions about potency-act composition in general:
(1) In emphasizing that these are cases of real distinction, we mean to affirm that this
distinction of principles is not totally dependent upon or posterior to the activity of the mind
distinguishing.
(2) As we have just seen, even in the case of matter-form composition, one should affirm
in general that form as act is just the actualization of matter as potency. In general, act in a
composite of potency and act is always potency actualized.
(3) In each of the cases of composition we have studied, we have been able to note that the
potency principle is a principle of reception and limitation. The principle of potency in each of the
cases of composition is the principle that accounts for the limited and determined manner in which
the actuality in question is realized. It is in this way that in each case, the principle of potency is
said to participate its act principle.
(4) As we have repeatedly emphasized, composition and real distinction do not imply real
separability or the possible independent existence of the principles distinguished. However, it can
be said that in the case of substance-accident composition, the substance can exist independently of
a given separable accident. Also, in the case of matter-form composition, prime matter is the
subject of substantial change; it is not separable in the sense of being capable of independent
existence, but it is capable of serving as the matter of a different substance.
Carl: Metaphysics 84
10. The Transcendentals
One of the most famous doctrines of Thomistic metaphysics (and indeed of medieval
metaphysics in general) is the theory of the transcendentals, which are the most common properties
of all the things that exist.
10.1. General Statement of the Theory of the Transcendentals
According to this theory, the following terms are common to every being in the categories:
being (ens), one (unum), true (verum), good (bonum), as well as (in some presentations) thing (res)
and something (aliquid). As we will see, St. Thomas holds that whatever exists shares in all of
these most common characteristics, and that in general the distinction between the transcendentals
is a distinction of reason rather than a real distinction. These most common properties are called
transcendental because they “transcend” the categories: that is, they are not limited to any one
category but are found in all of them.
It should be noted, at the start, that being (ens) is itself a transcendental: whatever is (or
exists) is a being. Ens as a transcendental is none other than what we have already called ens
commune, being in general, the being analogically common to all of the categories. We need not
say anything more about ens as a transcendental, given everything that has already been said about
ens commune.
A caveat
In giving a relatively brief consideration of the topic of the transcendentals, we are already
departing from the manner in which a number of authors have presented Thomistic metaphysics; I
speak of those who strongly emphasize the doctrine of the transcendentals as being as it were the
centerpiece of Thomistic metaphysics.71 Often in connection with this tendency, there arises a way
(different from that which has been proposed in this course) of explaining the very project of
metaphysics. One can express the project of an Aristotelian science by noting that it sets forth the
essence of its subject and then proceeds to demonstrate the properties of the subject, and one way
of conceiving of the project of metaphysics is that what it does is to demonstrate and examine
being’s properties, understood as the transcendentals.
While the doctrine of the transcendentals is very important in the teaching of St. Thomas, I
do not think that the transcendentals play quite this role in the project of metaphysics: they are not
the properties of being that are demonstrated by the science of metaphysics.72 After all, ens itself is
one of the transcendentals or most common things. I think it is better to say just that the
transcendentals belong to the subject of metaphysics, just as St. Thomas says that unity, act, and
potency are part of what is studied under ens commune by the metaphysician.
10.2. The De veritate on the Transcendentals
71For just one recent example of this tendency, see Jan Aertsen, Medieval Philosophy and the
Transcendentals: The Case of Thomas Aquinas, (New York: Brill, 1996).
72I would contend instead that the properties of ens commune demonstrated in metaphysics are its various
modes of composition and its dependence upon uncreated being.
Carl: Metaphysics 85
The classic text in which St. Thomas spells out in a systematic way his understanding of
the transcendentals is De veritate q. 1 a. 1, which asks what truth is (quid est veritas?) and whether
the truth is in every way the same as being (ens). He argues that it seems that the true is in every
way the same as being, and in the seventh objection arguing for this view, he argues as follows:
The problem that St. Thomas raises here—the problem of the addition to being—is the
same problem pointed out in our earlier explanation of why being cannot be a genus: it cannot be
the case that anything extraneous is added to being, because what is extraneous to being is nonbeing.
In the first sed contra of this article, St. Thomas writes:
A “nugation” is the meaningless repetition of two words that mean exactly the same thing.
For example, “human man” would be a nugatory expression. But “true being” or “being is true”
are not instances of just meaningless repetition, and so the true is not in every way the same as
being.
St. Thomas begins his response by noting that just as one attempts to reduce propositions
to self-evident principles—that is, one seeks demonstrations—so also in one’s investigation of
what something is, it is necessary to reduce or resolve what one knows to what is most known. But
according to Avicenna, that which the intellect first conceives as what is most known and that into
which it resolves all its conceptions is ens.73 As a consequence, all the other concepts of the
intellect are understood from addition to ens. But nothing extraneous to ens can be added to ens, in
the way in which a difference is added to a genus or an accident to a subject, since every nature is
essentially an ens: this is why Aristotle asserts in the Metaphysics that ens cannot be a genus.
St. Thomas explains that addition is made to ens, not as it were by adding something
extraneous to ens, which is impossible; but some things (that is, concepts or terms) said to add to
ens by expressing or signifying some mode of ens which is not expressed by the name ens. He
explains that this occurs in two ways.
73This priority is not in the order of time, but in the order of resolution. One should not take this claim about
the priority of the concept of ens as contradicting our earlier discussion of how being is known: ens is a
complex concept that presupposes the act of judgment, because the notion of ens is habens esse or id
quod est.
Again, if they were not in every way the same it would necessarily be the case that true adds
something beyond being; but the true adds nothing beyond being. . . .
On the contrary, the useless repetition of the same thing is nugatory (vain or meaningless); if
therefore true were the same as being, it would be nugatory when one says “true being,” which is
not the case; therefore they are not the same.
Carl: Metaphysics 86
Ways in which a concept or term can express something which ens does not express
(1) Categories: What the term or concept expresses is a certain special mode of being
(ens). St. Thomas explains that there are diverse grades of being (ens) according to which one
understands diverse modes of existing (esse), and under these modes are understood the diverse
genera of things: for example, substance (as a term or concept) does not add to being (ens) some
difference which designates a nature superadded to being (ens), but by the name of substance a
certain special mode of existing (esse) is expressed, namely ens per se, and the same goes for the
other categories. In this way, then, the ten categories (and all of the concepts that fall under each of
the ten categories) add to being, not by adding something extraneous to being, but by expressing
some mode of existing that is not explicitly expressed by the name being.
(2) Transcendentals: What the term or concept expresses is a general or common mode that
is consequent upon every being (ens). This occurs in two ways:
(a) First, according to what follows upon every being (ens) in itself.
And this occurs in two ways:
(i) First, the name or concept can affirmatively express the essence or that
according to which the thing is said to exist: in this way the name thing (res) is
THING imposed on being (ens). St. Thomas cites Avicenna, who holds that ens is taken
(RES) from the act of existing (actus essendi) whereas the name thing (res) expresses the
quiddity or essence of a being (ens).
(ii) Second, the name or concept can negatively express the lack of division that
ONE follows absolutely upon any being: insofar as something is a being, it is undivided.
(UNUM) The name that expresses this undivided character of being (ens) is one (unum). The
notion of one is undivided being.74
(b) Second, according to what follows upon a being (ens) in its relation to something else.
And this occurs in two ways:
(iii) First, insofar as every being (ens) is distinct from every other being, and in
SOMETHING this way the name something (aliquid) expresses, as it were, some other thing
(ALIQUID) (aliud quid). Whereas the name one expresses undivided being, the name
something expresses the distinction of this being from every other being.
(iv) Second, insofar as every being (ens) is related to the human soul. But there are
two powers of the human soul according to which beings are related to it:
Thus this kind of addition to being is divided into two ways:
(1) First, according to the relation to the appetitive power in the soul, being
GOOD insofar as it corresponds to the appetite is called good (bonum). This
(BONUM) follows Aristotle’s characterization of the good as what all things desire.75
(2) Second, according to the relation to the knowing power in the soul,
TRUE being insofar as it corresponds to a knowing power is called true (verum).
(VERUM) True thus adds to the notion of being (ens) the notion of conformity with
an intellect.
Thus, each of the transcendental terms (besides ens itself) adds something to the notion of
being that is not explicitly expressed by the term being (ens). This is not a matter of adding
something extraneous to being, but rather just expressing something not expressed by the term
being. For this reason, the transcendentals besides ens are not really distinct from ens, but are
distinct only according to reason. Thus, insofar as a being is a being, it is one, a thing, something,
74The origin of the doctrine of the transcendental character of one is Aristotle’s Metaphysics, in which he
emphasizes repeatedly that insofar as a being is, it is one.
75This is from the first line of the Nicomachean Ethics.
Carl: Metaphysics 87
good, and true.
10.3. The Order of the Transcendentals
In another text, DV 21.3, St. Thomas notes that there is an order among the
transcendentals, in that each of the transcendentals (besides ens) not only adds to being, but each
adds to being in a way that presupposes the previous transcendental:76
The term one presupposes being, because it adds to being the notion of indivisibility. True
adds to being the notion of relation to an intellect, but a thing’s intelligibility is a consequence of its
unity: and so the true adds to being in a way that presupposes unity. Similarly, the good
presupposes the true, in that whereas true adds to being the notion of a thing’s perfection as an
instance of a specific kind, good presupposes this, but also adds the notion of perfection in a thing’s
actual existence. That is, to name something true is to indicate its specific conformity with
intellect; to name it as good is to indicate the perfection that it possesses in its existence, in
accordance with which it is related to appetite as desirable.
This order among the transcendentals is important as a central issue in the discussion of
whether beauty is also a transcendental. In a number of texts, St. Thomas makes clear that beauty
adds something to good; but he never says that beauty adds to or is convertible with being. One
argument in favor of beauty’s transcendental character is to note that every transcendental
presupposes the former transcendental. Thus, if beauty adds something to good, it can also be said
to add something to being, just as good can be said to add something to true.77
76The translation is the Schmidt translation, available at www.dhspriory.org/thomas/QDdeVer21.htm.
77I have no settled view about whether beauty is a transcendental or whether St. Thomas thought of beauty as
a transcendental. although I lean towards a negative answer in both cases.
If the true and good are considered in themselves, then the true is prior in meaning to good since
the true perfects something specifically, whereas good perfects not only specifically but also
according to the existence which the thing has in reality. Thus the character of good includes more
notes than that of the true and is constituted by a sort of addition to the character of the true. Thus
good presupposes the true, but the true in turn presupposes the one, since the notion of the true is
fulfilled by an apprehension on the part of the intellect, and a thing is intelligible in so far as it is
one; for whoever does not understand a unit understands nothing, as the Philosopher says. The
order of these transcendent names, accordingly, if they are considered in themselves, is as follows:
after being comes the one, after the one comes the true; and then after the true comes good.
Carl: Metaphysics 88
10.4. Being and One in Aristotle’s Metaphysics
In In Meta. 4.2, St. Thomas introduces the Aristotelian discussion of being and unity by
observing that Aristotle’s purpose is to show that one and many, same and different are to be
studied by the first philosophy, just because to study these is to study being:
Hic procedit ad ostendendum quod ad
considerationem unius scientiae pertinent
considerare huiusmodi communia, scilicet unum et
multa, idem et diversum.
Here he proceeds to show that it pertains to the
consideration of one science to consider common
[things] of this kind, namely one and many, same
and different.
(I would emphasize that your translation of the Commentary on the Metaphysics
introduces the language of attributes to describe one and many, same and different in this text: St.
Thomas simply refers to them as communia, the common items.)
Throughout In Meta. 4.2, it is emphasized that being and unity are the same in reality but
differ in concept or ratio, following Aristotle’s remarks in Metaphysics 4.2 to this effect. In this
early book of the Metaphysics, Aristotle’s purpose is not to consider unity as such, but merely to
establish that it pertains to the metaphysician to consider unity, because unity and being are the
same in nature and differ only in concept.
We can summarize Aristotle’s claims in 4.2 and St. Thomas’s commentary as follows:
(1) Being and unity are the same in nature and differ only in concept. We find two
arguments in In Meta. 4.2 for this claim. The first is as follows:
Quod autem sint idem re, probat duabus rationibus,
quarum primam ponit ibi, idem enim, quae talis
est. Quaecumque duo addita uni nullam
diversitatem afferunt, sunt penitus idem: sed unum
et ens addita homini vel cuicumque alii nullam
diversitatem afferunt: ergo sunt penitus idem.
Minor patet: idem enim est dictum homo, et unus
homo. Et similiter est idem dictum, ens homo, vel
quod est homo: et non demonstratur aliquid
alterum cum secundum dictionem replicamus
dicendo, est ens homo, et homo, et unus homo.
But that they are the same in reality, he proves by
two arguments, the first of which he offers where
[he says] “For the same,” which [argument] is as
follows. Any two [things] which, added to one
[other thing], cause no difference, are entirely the
same: but and and being added to man or to any
other [thing] cause no difference: therefore they are
entirely the same. The minor is evident: for it is the
same to say man and one man. And similarly it is
the same to say man-being or that which is man:
and something else is not expressed when in
speaking we repeat in speech, it is a man-being,
Carl: Metaphysics 89
and a man, and one man.
Aristotle and St. Thomas’s point is that to call the same thing a man (homo), or one man
(unus homo), or a man being (ens homo) does not signify anything different in reality: whereas to
say “tall man” as opposed to “one man” does signify something different in reality. St. Thomas,
following Aristotle, goes on to note that this can also be seen by noting that whenever a man is
generated or corrupted, it is one man that is generated or corrupted. St. Thomas then clarify that
there is a distinction between being and one, but this is a conceptual distinction rather than a
distinction in reality.
The second argument is as follows:
Quaecumque duo praedicantur de substantia
alicuius rei per se et non per accidens, illa sunt
idem secundum rem: sed ita se habent unum et ens,
quod praedicantur per se et non secundum
accidens de substantia cuiuslibet rei. Substantia
enim cuiuslibet rei est unum per se et non
secundum accidens. Ens ergo et unum significant
idem secundum rem.
Any two things which are predicated of the
substance of some thing per se and not per
accidens, are the same in reality: but thus are one
and being, which are predicated per se and not
secundum accidens of the substance of each thing.
For the substance of each thing is one per se and
not secundum accidens. Therefore being and one
signify the same [thing] in reality.
St. Thomas goes on to explain that one is not predicated per accidens, because “a thing’s
substance is one and a being of itself and not by reason of something added to it.” That is, insofar
as a substance is, it is a being, and it is one. Being and one are not something belonging to a
substance by virtue of an accident—which is all that per accidens means here—but by virtue of the
substance itself.
(2) Nevertheless, these terms are not entirely synonymous. It is not nugatory to say “one
man.” Being and one do differ in concept, just not in reality.
(3) The unity that is the principle of number is not the same as the unity that is convertible
with being:
Unum igitur quod est principium numeri, aliud est
ab eo quod cum ente convertitur. Unum enim quod
cum ente convertitur, ipsum ens designat,
superaddens indivisionis rationem, quae, cum sit
negatio vel privatio, non ponit aliquam naturam
enti additam. Et sic in nullo differt ab ente
secundum rem, sed solum ratione. Nam negatio vel
privatio non est ens naturae, sed rationis, sicut
dictum est. Unum vero quod est principium numeri
The one therefore which is the principle of number
is different from that which is convertible with
being. For the one which is convertible with being,
designates being (ens) itself, adding the notion of
indivision, which, since it is a negation or
privation, does not posit some nature added to
being. And thus in no way does it differ from being
in reality, but only in ratio. For a negation or
privation is not a being of nature, but of reason, as
Carl: Metaphysics 90
addit supra substantiam, rationem mensurae, quae
est propria passio quantitatis, et primo invenitur in
unitate.
was said. But the one which is the principle of
number adds to substance the notion of measure,
which is the proper attribute of quantity, and is first
found in a unity [the unit].
(4) There are the same number of “parts” or “species” of unity as there are of being.
Sameness, equality, and likeness correspond to substance, quantity, quality:
Dicit ergo primo, quod ex quo unum et ens idem
significant, et eiusdem sunt species eaedem,
oportet quod tot sint species entis, quot sunt
species unius, et sibiinvicem respondentes. Sicut
enim partes entis sunt substantia, quantitas et
qualitas etc., ita et partes unius sunt idem, aequale
et simile. Idem enim unum in substantia est.
Aequale, unum in quantitate. Simile, unum in
qualitate Et secundum alias partes entis possent
sumi aliae partes unius, si essent nomina posita.
He says first therefore, that because one and being
signify the same [thing], and because of the same
[thing] the species are the same, it is necessary that
there be as many species of being as there are
species of unity, corresponding to one another. For
just as the parts of being are substance, quantity,
and quality, etc., so too the parts of one are same,
equal, and like. For “same” is one in substance.
“Equal” is one in quantity.” “Like,” one in quality.
And thus the other parts of one could be
understood according to the parts of being, if they
were given names.
(5) It can thus be concluded that it pertains to the metaphysician to consider unity along
with being:
Et sicut ad unam scientiam, scilicet ad
philosophiam, pertinet consideratio de omnibus
partibus entis, ita et de omnibus partibus unius,
scilicet eodem et simili et huiusmodi.
And just as the consideration of all the parts of
being pertains to one science, namely philosophy,
so too [the consideration] of all the parts of one,
namely sameness, likeness, and others of this kind.
Carl: Metaphysics 91
10.5. Truth as a Transcendental
As seen above, the true is included by St. Thomas in his list of transcendentals or
communissima. True is convertible with being, and it adds to being (ens) the relation of conformity
to an intellect. True expresses something not expressed by the term being, but it does not add
anything extrinsic or determining to being: every being is true, as a being.
Truth as a transcendental is often referred to by Thomists, therefore, as truth of being. This
truth of being can be distinguished from truth of intellect, which is the meaning of truth according
to which it is said that an intellect is true (or to be more precise, that an intellect’s judgment is true).
Truth of intellect and truth of being
It is primarily truth of intellect that is at issue in ST 1.16 aa. 1-2, where St. Thomas asks
whether truth resides only in the intellect and whether truth resides only in the intellect composing
and dividing. In light of the thesis that truth is a transcendental, it may at first be surprising that St.
Thomas claims that truth is only in the intellect and only in the intellect composing and dividing
(i.e., judging). On both of these points, as indicated by the two sed contra arguments, St. Thomas is
influenced by the teaching of Aristotle, according to whom (a) truth is in the intellect rather than in
things, and (b) there is truth in the intellect’s composing and dividing, but not in the knowledge of
what something is.
In the body of a. 1, St. Thomas gets at his point by contrasting the true with the good.
Whereas the good denotes that towards which appetite tends, the true denotes that towards which
intellect tends:
(1) The good is in the object desired, because appetite inclines the one who desires towards
the possession of the object of desire. The terminus of appetite is thus in the object desired. It is
therefore the goodness (or lack thereof) of an object desired that makes the appetite good (or not).
Good is in the object insofar as it is related to appetite, but it is the goodness of the object that
makes appetite good, not vice versa.
(2) By contrast, knowledge is the existence of the known (in some way) in the knower.
Knowledge or truth is therefore not in the thing known, but in the knower, insofar as the known
object exists in the intellect of the knower. Therefore the terminus of intellectual activity is not in
the thing known, but in the intellect. Thus, although the intellect is true insofar as it is conformed
to the thing understood, nevertheless the character of the true is primarily in the intellect and is in
the thing known by way of derivation. A being is called true insofar as it is related to some intellect
that knows it, but truth is first in the intellect and secondarily in the thing.
At this point, St. Thomas draws a distinction between two ways in which an object might
be related to an intellect. He notes that a thing understood (res intellecta) can be related to an
intellect either per se or per accidens.
(a) If a thing understood is related to an intellect that just happens to know it (or more
generally to an intellect by virtue of which it is something knowable—cognoscibilis), then this is
only a per accidens relation. That is, a given object can be knowable or actually known by a
human intellect, without in any way depending upon that intellect for its existence.
Carl: Metaphysics 92
(b) By contrast, a thing understood can be related to an intellect in such a way that the
thing depends upon that intellect for its existence or being (dependet secundum suum esse). In this
case, the relation to the intellect is per se, not per accidens. St. Thomas notes that this can occur
even with the human intellect: for example, a house depends upon the intellect of the architect. In
general, St. Thomas allows that artificial things are called true according to their relationship to the
intellect of the artisan.
But what we have called truth of being or transcendental truth is not by reference or
relation to the human intellect, because a given being’s relation to a human intellect is only per
accidens, not per se. However, all beings other than God are related to the divine mind as to that
upon which they depend for their very existence. Thus, “natural things are said to be true, insofar
as they possess a likeness of the species which are in the divine mind.” Truth is ultimately
primarily in the intellect, but in the divine intellect rather than the human intellect, because the
divine intellect is the principle upon which everything else depends for existence.
10.6. Additional Comments Concerning Good as Transcendental
As we have seen, good is also a transcendental term or notion. Another way in which this
thesis is expressed is the claim that being and good are convertible: that is, one can generally
replace any instance of ens in a proposition with bonum and preserve the truth of the proposition.
For example: the rock is a being the rock is good. If something exists or is a being, it can also
be said to be good.
This claim concerning the transcendental character of the good is foundational for
Thomistic ethical philosophy: what is good for a human being (or for anything else) is the
fulfillment or perfection of his (or its) being. To become good in the most complete way is to come
to be in the most complete way. St. Thomas spells this out nicely in ST 1.5.1, which asks whether
good differs from being (ens) in reality (secundum rem).
In the reply to the first objection in this text, St. Thomas adds a distinction concerning the
convertibility of being and good. Although being and good are the same in reality, nevertheless
because they differ from each other in thought, it is not the case that something is called being
simply (ens simpliciter) or good simply (bonum simpliciter) in the same way. Ens properly
expresses that something exists in act (ens dicat aliquid proprie esse in actu), and because act is
correlated to potency, a thing is called a being simply (ens simpliciter) insofar as it is distinguished
from that which is only in potency: thus ens simpliciter signifies a thing having substantial esse.
By contrast, any further actuality that a substance receives is not ens simpliciter (which is
its substantial being), but relative being or qualified being (ens secundum quid). That is, a
substance is further actualized by receiving accidents. For example, as St. Thomas notes, “to be
white” signifies relative or qualified existence (esse secundum quid), because “to be white” is not
the immediate actualization of what is in potency alone, because what is or becomes white must
possess substantial existence, esse simpliciter.
St. Thomas applies this distinction between ens simpliciter and ens secundum quid to the
notion of the good. St. Thomas notes that “good signifies the ratio of the perfect, which is
desirable.”78 Therefore, good simply (bonum simpliciter) signifies what is perfect, and what has its
78It is worth noting that this characterization of good as perfect being, which is desirable, adds something to
the account given in the text in the De veritate. For commentary on the importance of this development,
Carl: Metaphysics 93
ultimate perfection is said to be good simply; by contrast, what lacks the ultimate perfection that it
ought to have (although it has some perfection just insofar as it exists in act) is not said to be
perfect simply (perfectum simpliciter) or good simply (bonum simpliciter), but rather perfect and
good relatively or in a qualified way (secundum quid). Therefore, St. Thomas concludes that a
thing according to its primary esse (which is its substantial esse) is said to be ens simpliciter and
bonum secundum quid, insofar as it is a being (ens). But according to its ultimate actuality,
something is called ens secundum quid and bonum simpliciter.
These qualifications to the convertibility of being and good have at least two important
implications:
(1) First, this way of explaining the transcendental character of the good serves as the
appropriate metaphysical foundation for philosophical ethics. A human being’s ultimate perfection
and simple goodness is found not in its substantial being, but rather in the acquisition of further
actuality, of actuality that perfects human nature.
(2) Second, this qualification emphasizes that although being in general (ens commune)
and good in general (bonum in communi) are convertible, nevertheless in any finite being, being
simpliciter and good simpliciter are not identical. There is thus (as St. Thomas explains in q. 5 a. 4)
a relationship of final causality to the good simply in finite beings: every finite being is ordered to
the acquisition of its ultimate perfection and simple goodness, which are not identical with its
substantial being. As we will see later in our course, only in God are being simply and goodness
simply identical, because God is absolutely actual and perfect in Himself, without receiving any
actuality or perfection distinct from his esse.
see Rudi te Velde, “The Concept of the Good according to Thomas Aquinas,” Die Metaphysik und das
Gute, ed. Jan Aertsen, 79-104.
Carl: Metaphysics 94
11. How God is Known through Natural Reason
We now turn our attention from the study of the subject of metaphysics itself to
consideration of the first cause of being. We have already seen an indication of how the
examination of ens commune can lead to the assertion of the existence of God in the De ente et
essentia c. 4, where from the real composition of essence and esse in finite beings it is argued that
there must be a being whose esse is its essence, a subsistent esse that is the efficient cause of esse
in all other things that receive the actus essendi.
Curiously, St. Thomas does not employ this exact means of arguing for God’s existence
later in his career: that is, he does not set out to prove the existence of subsistent esse immediately
from the metaphysical structure of ens commune. One of the questions that we will address in our
consideration of natural theology is why St. Thomas later shows a preference, in practice, for other
ways of arguing for God’s existence.
11.1. Different Ways in Which God is Known
One of the first things that will need to be said concerning the knowledge of God
possessed by human beings in this life is that God’s existence is not strictly speaking self-evident.
In preparing to examine this topic, we should first note that St. Thomas carefully distinguishes
between different ways in which the existence of God can be known in this life.
The manner in which God’s existence is known to all
We turn first to a text from St. Thomas’s Lectura romana, d. 17 q. 1 a. 1.79 This text
distinguishes for us between different ways in which God can be known, in order to answer the
question of whether a supernatural light is necessary in order to love God. Because something is
loved only insofar as it is known, the ways in which God can be loved by human beings will
depend upon the various ways in which God can be known by human beings.
First, St. Thomas says that there is a knowledge of God that is possessed by all human
beings from the beginning of their lives, insofar as in knowing any created being there is a
knowledge of the creating God who creates that being. Because St. Thomas says that this is a
knowledge only of God’s effects, it seems that this knowledge of God is only implicit.
Corresponding to this kind of knowledge of God is a first way of loving God: insofar as one loves
a creature, one can be said to love God. This love, like the knowledge upon which it is founded,
seems to be implicit. St. Thomas says that both this knowledge and this love are possessed
naturally by all men. Insofar as any created thing is known or loved, in a sort of implicit way God
is known and loved, as the creating cause of these created things. In terms of what a human being
explicitly believes and loves, however, this implicit knowledge and love of God is consistent with
denying the existence of God and failing to explicitly love Him.
Second, St. Thomas says that there is a knowledge of God Himself, but from His effects.
This kind of knowledge occurs through the inquiry of reason, by which one proceeds from the
knowledge of effects to a knowledge of God. St. Thomas notes that this is the kind of knowledge
of God possessed by “the philosophers and other wise men,” who arrived at such a knowledge of
God through natural reason, insofar as it is possible to do so. Corresponding to this kind of
79The Lectura romana is St. Thomas’s incomplete secondary commentary on the Sentences. He began to
offer this commentary during his teaching in Rome, before abandoning the project to begin composition
of the Summa theologiae. The Lectura romana was lost almost immediately after the death of St.
Thomas, but a copy of it was found in the 20th century, and it was edited and finally published in 2006.
Carl: Metaphysics 95
knowledge of God is a love of God that is explicit and is founded upon this natural knowledge of
God through the inquiry of reason. We will comment more on this knowledge of God from His
effects shortly.
Third, there is the knowledge of God Himself that exceeds the proportion of any His
effects: such a knowledge goes beyond any knowledge that can be had concerning God by
reasoning from created effects. St. Thomas notes that this knowledge is not in men naturally; nor is
it acquired through the inquiry of reason; but it is infused through a supernatural light, i.e., through
the supernatural light of faith in this life and of the beatific vision given to the blessed.
Corresponding to this supernatural knowledge of God is a supernatural love of God, through which
one has a society or friendship with God. Such a knowledge and love are possible only by grace.
That every human being knows and loves God implicitly in the first way does not
contradict the fact that a given human being can fail to know and love God in the second and third
ways. The reason that this is a possibility is because, as St. Thomas explains, the existence of God
is not self-evident (per se notum) to us in this life.
St. Thomas also comments on the implicit and confused knowledge of God possessed by
all human beings in Summa theologiae I q. 2 a. 1 ad 1:80
11.2. That God’s Existence is not Self-evident to Us
St. Thomas addresses the question of whether God’s existence is self-evident a number of
times during his career. He takes as an advocate for the view that God’s existence is self-evident St.
Anselm of Canterbury, who famously proposed an argument for God’s existence that has, for better
or worse, come to be called the ontological argument.
St. Anselm’s argument
Although it is beyond our ability to examine this argument (in either of the two
formulations in which St. Anselm offers it) at this time, we can give a broad overview of the first
version of the argument and the reason that St. Thomas gives in criticizing it. According to first
formulation of St. Anselm’s argument, found in c. 2 of his Proslogion, the existence of God can be
known in an immediate way, just as soon as one recognizes that God is that greater than which
80All quotations from the Summa theologiae in this section of the notes are from the English Dominicans
translation, with occasional modification.
To know that God exists in a general and confused way is implanted in us by nature, inasmuch as
God is man’s beatitude. For man naturally desires happiness, and what is naturally desired by man
must be naturally known to him. This, however, is not to know absolutely that God exists; just as to
know that someone is approaching is not the same as to know that Peter is approaching, even
though it is Peter who is approaching; for many there are who imagine that man’s perfect good,
which is happiness, consists in riches, and others in pleasures, and others in something else.
Carl: Metaphysics 96
none can be thought. We will consider this argument according to how St. Thomas presents it in
Summa theologiae I q. 2 a. 1 obj. 2:81
St. Thomas’s presentation of St. Anselm’s argument is formulated in terms of the
Aristotelian understanding of self-evidence (notitia per se). A proposition is self-evident (per se
notum) when the proposition’s truth is evident just as soon as one understands the meaning of the
terms in the proposition. For example, the proposition “Every whole is greater than its part” is seen
to be true just as soon as one knows the meanings of the terms whole and part.
St. Thomas formulates the Anselmian argument for God’s existence in this way: as soon as
one knows that the word God signifies “that thing than which nothing greater can be conceived,”
he will at once see that God must exist, because for a thing to exist both in the mind and in reality
is greater than for it to exist only in the mind. That is, if one were to conceive of God as a being
existing only in the mind, this would contradict the claim that God is the greatest conceivable
being: and therefore God must exist.
St. Thomas criticizes the Anselmian argument in the following way:
81For Fr. Wippel’s comments on St. Thomas’s presentation and criticism of St. Anselm’s argument, see
Wippel 391-99.
Those things are said to be self-evident which are known as soon as the terms are known, which
the Philosopher says is true of the first principles of demonstration. Thus, when the nature of a
whole and of a part is known, it is at once recognized that every whole is greater than its part. But
as soon as the signification of the word “God” is understood, it is at once seen that God exists. For
by this word is signified that thing than which nothing greater can be conceived. But that which
exists actually and in the mind is greater than that which exists only in the mind. Therefore, since
as soon as the word “God” is understood it exists in the mind, it also follows that it exists actually.
Therefore the proposition “God exists” is self-evident.
Perhaps not everyone who hears this word “God” understands it to signify something than which
nothing greater can be thought, seeing that some have believed God to be a body. Yet, granted that
everyone understands that by this word “God” is signified something than which nothing greater
can be thought, nevertheless, it does not therefore follow that he understands that what the word
signifies exists actually, but only that it exists mentally. Nor can it be argued that it actually exists,
unless it be admitted that there actually exists something than which nothing greater can be
thought; and this precisely is not admitted by those who hold that God does not exist.
Carl: Metaphysics 97
First, St. Thomas notes that it is not evident to everyone that the name God signifies
“something than which nothing greater can be thought.” For example, some people have thought
that God—the highest being or the being guiding the universe—was a body; for example, the
Stoics thought of God as a body, even though they attribute intelligence and providence to God.
Granting for the sake of argument that everyone understands the signification of the name
God in the way that St. Anselm claims, still, it does not follow that what is signified by this word
exists actually, but only that it exists in the mind. In other words, St. Thomas will not allow that
one can reach an inference about the actual existence of God from the thought of a being greater
than which none can be thought, because it is not necessarily the case that anything exists in reality
that is the greatest conceivable thing. This is precisely what those who deny the existence of God
will deny: they deny that there is a correspondence between what is the greatest in reality and what
is the greatest conceivable thing; they deny that there is in reality something greater than which
nothing can be thought.
God’s existence is not self-evident to us
As St. Thomas explains in the body of Summa theologiae I q. 2 a. 1, something can be selfevident in two ways: (1) self-evident in itself, but not to us; (2) self-evident in itself, and to us. St.
Thomas reaffirms the Aristotelian notion of self-evidence a proposition is self-evident when the
proposition is known to be true as soon as the meaning of the terms in the proposition are known.
For example, “man is an animal” is seen to be true just as soon as one understands what a man is
and what an animal is. However, it should be noted that the meanings of these terms—man and
animal—are not immediately known to all. Even fewer will see the self-evidence of this
proposition: “Incorporeal substances are not in a place.”
St. Thomas then explains that the proposition “God exists” is self-evident in itself, because
God’s essence is His very esse, as is shown later in Summa theologiae I q. 3 a. 4. But God’s
existence is not self-evident to us, because His essence is not known by us in this life. These two
claims may seem to be in tension: that God’s essence is His esse, and that we do not know God’s
essence in this life. Although we can know the truth of the former proposition—we can know that
God’s essence is identical with His esse—nevertheless we do not know God’s essence in the way
that we know the essence of a man. That is, God’s esse in itself—God as He is in Himself—is not
known to us in this life. In this way the knowledge of God in this life is contrasted with the
knowledge of God promised to the blessed, that He will be seen face to face.
Therefore, St. Thomas concludes, it must be that God’s existence is known by us through a
demonstration from His effects. We turn now to a discussion of this topic.
11.3. How God’s Existence is Demonstrated
St. Thomas discusses how God’s existence can be demonstrated in the next article of the
Simma theologiae, I q. 2 a. 2. There, following Aristotle’s doctrine in the Posterior Analytics, he
explains that there are two kinds of demonstration:
(1) There is demonstration propter quid, in which one demonstrates something through its
cause, arguing from the cause to the effect. In this kind of demonstration, one’s reasoning process
parallels the very order of reality, insofar as a cause precedes its effect in reality (not always by a
temporal priority, but by a causal priority), one’s reasoning in a demonstration propter quid
Carl: Metaphysics 98
proceeds from what is prior in reality to what is posterior in reality. It is for this reason that one can
also call a demonstration propter quid a demonstration a priori. A demonstration propter quid
allows one to know not just that the conclusion is true, but also why it is the case. It should also be
noted that it is a requirement of demonstration propter quid that one’s knowledge of the cause be a
knowledge of the quiddity or essence of the cause: one has to know what the cause is in order to
demonstrate a truth concerning the effects of the cause.
(2) There is demonstration quia, in which one demonstrates only that something is the
case, by arguing from what is prior relative to us, i.e., effects. A demonstration quia presupposes no
knowledge of what the cause is, but instead establishes just that something is true concerning the
cause. In a demonstration quia, the order of one’s knowledge does not parallel the order of reality,
because in reality causes are prior to effects; whereas in a demonstration quia the knowledge of the
effect is prior to the knowledge of the cause.
Because God’s existence is not self-evident to us (which is because God’s essence is not
known to us in this life), St. Thomas asserts that God’s existence can only be known by us through
a demonstration quia rather than a demonstration propter quid. Indeed, it should be noted that no
demonstration propter quid concerning God’s existence is possible at all (even if one had
knowledge of the essence of God), because if one knew the essence of God, then His existence
would be self-evident. Furthermore, as will be shown later, God’s existence is not caused, and
therefore there can be no demonstration from a cause to God’s existence understood as an effect.
Every argument for God’s existence will therefore proceed from a knowledge of certain
created realities, which will come to be recognized as effects that can only be caused by the being
that we call God. We will see St. Thomas’s procedure in constructing such arguments when we turn
to consideration of his ways of proving God’s existence in Summa theologiae I q. 2 a. 3.
11.4. The Impossibility of Quidditative Knowledge of God
Before proceeding to a consideration of argumentation for God’s existence, we should
consider a claim that has already been made—that in this life we cannot know what God is—but
which has not been directly defended. Indeed, in the texts of the Summa theologiae that we have
examined so far, St. Thomas takes it for granted that in this life a quidditative knowledge of God
(that is, a knowledge of what God is) is impossible. In other contexts, however, he explains why it
is that such knowledge of God is impossible in this life.
The meaning of quidditative knowledge
To begin, we should clarify what we mean when we say that quidditative knowledge of
God is impossible for human beings in this life. By this, we mean that a human being cannot know
what God is, in the technical sense in which one knows what something is by knowing its essence.
For example, to know what man is is to know that man is a rational animal with flesh and bones,
etc. If one knows that man is risible, or musical; or if one knows that this man is tall, or white—all
of these instances of knowledge about man fall short of a quidditative knowledge of what man is
essentially. When we deny that we are capable in this life of knowing what God is, we mean that
we cannot possess a knowledge of God’s essence like the knowledge of the essence of a man
expressed by the definition of man.
Why quidditative knowledge of God is impossible in this life
Quidditative knowledge of God, in this strict and technical sense, is impossible in this life.
In In DT 1.2, St. Thomas offers an explanation as to why this is the case. He begins by offering a
division of the ways in which a thing can be known:
Carl: Metaphysics 99
(1) A thing can be known through its proper form, as when the eye sees a stone through the
species of a stone.
And this in two ways:
(a) Through the very form of the thing itself, as God knows Himself and an angel
knows itself. (That is, the self-knowledge of God and of the angels is not in any
way mediated by any form other than their own essences.)
(b) Through a form which is other than the thing known.
Either:
(i) When the form has been abstracted from the thing, as how the human
intellect knows the essence of something such as a stone
(ii) When the form is impressed on the intellect by a thing, which is how
an immaterial thing would be known in a direct way by the human
intellect.
(2) A thing can be known through some other form that is similar to the thing, as when a
cause is known through its effect; for example, as a man is known through the form of an image in
a mirror.
And this in two ways, according to two kinds of effects:
(a) There are effects adequate to the power of the cause, and through such an effect
the power of the cause can be fully known, and consequently the essence of the
cause.
(b) There are effects that are not fully equal to their cause, and through such an
effect neither the power nor the essence of the cause can be comprehended; instead
it can only be known that the cause exists.
Based upon this division of the ways in which a thing can be known—that is, of the
various forms through which a thing can be known—St. Thomas proceeds to explain why the
quiddity of God cannot be known in this life through any of the ways outlined above. He first
explains that because the human intellect, in the present life, has a determined relation to forms
abstracted from sensible things—because human understanding depends upon phantasms present
in the imagination, which are derived from sense experience—it cannot be the case that we would
know God through His very essence in this life, because God is immaterial and therefore cannot be
sensed. We know the essence of a stone by abstracting a form that is a likeness of the essence of a
stone from a phantasm of the stone, which is derived from our sense experience of the stone. No
such sense experience is possible concerning God, and so it cannot be the case that we could know
God through His essence in this life.
By this explanation, St. Thomas has excluded both (1-a) and (1-b-i) from the division
above: God is not known through His very essence in this life (because this cannot be known
through the senses), and He is not known immediately through any form abstracted from matter.
However, it is the case that the blessed in heaven, who enjoy the beatific vision, know God through
His very essence, the way identified as (1-a) above. But no one can ever know the essence of God
in the way identified as (1-b-i).
Next, St. Thomas excludes the possibility that God’s essence could be known, in this life,
by any form impressed by God upon the human intellect, by noting that God infinitely transcends
every created form (a form distinct from His own essence and impressed on the mind would be a
created form). Therefore, it cannot be the case that God would be made known in His essence even
through a form supernaturally impressed on our intellect in this life. St. Thomas also excludes the
possibility that a form that is a likeness of an angel (a pure intelligence) could make God’s essence
Carl: Metaphysics 100
known to us, because the human intellect is naturally proportioned (or connaturally related) to
knowing through phantasms.
At this point, St. Thomas has excluded every kind of proper form through which a thing
can be known with regard to knowledge of the essence of God: in this life we cannot see the
essence of God itself; we cannot abstract a form from sense experience through which we would
know the essence of God; and we cannot know the essence of God even by any form impressed on
our intellect, whether by God or by angels. What this leaves, then, is only the possibility identified
as (2) above, that God can be known through His effects.
But because no created effect is equal to God, it cannot be the case that God’s power can
be comprehended from a knowledge of created effects. Without a comprehensive understanding of
the power of God as the cause, His essence will remain unknown to us, even though we can know
from such effects that He exists.
Thus, the impossibility of quidditative knowledge can be explained from two theses, one
concerning the manner in which human beings know in this life, and the other concerning the
comparison of creatures to God:
(1) All human knowledge in this life (except that resulting from forms impressed on the
mind by God or angels) is derived from sense experience, because the human intellect is naturally
proportioned and connaturally related to knowledge through phantasms, which are produced in the
imagination as the fruit of sense experience. It is for this reason that St. Thomas will often say that
the natural object of the human intellect is the quiddity of corporeal substances, because these are
the things that can be known through the senses.
(2) Every effect falls short of the infinite perfection of God, because God cannot create
another God. Every creature is finite, and thus no knowledge of God from created effects can ever
lead one to a knowledge of what God is in Himself. Even as regards that knowledge resulting from
forms impressed on the mind by God or angels, such forms cannot result in a knowledge of what
the divine essence is, because these forms are also created forms that fall short of their divine
cause. The only way that God can be known in His essence is through the beatific vision of that
essence in the life to come.
Concluding remarks
We have now explained why St. Thomas denies the possibility that God’s essence can be
known in this life, and as we have seen, this claim is presupposed in his argumentation for (1) the
claim that God’s existence is not self-evident and (2) the claim that God’s existence can only be
demonstrated from created effects. Now that we have some understanding of how St. Thomas
thinks the existence of God can be demonstrated, we will proceed to a consideration of his first
way of arguing for God’s existence.
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12. Argumentation for God’s Existence: the First Way
In Summa theologiae q. 2 a. 3, St. Thomas famously proposes five ways in which the
existence of God can be proved. In general, what the five ways share in common is that each of
them proceeds from some feature of reality, arguing that this feature must be the effect of a cause
that we understand to be God. The five ways thus argue from the following features of reality:
First way from motion
Second way from the nature of efficient causality
Third way from possibility and necessity in things
Fourth way from the gradation found in things
Fifth way from the governance of the world
12.1. The First Way: Argument from Motion
We will begin by offering a brief commentary on the text of the first way. Our treatment of
this argument will be somewhat cursory, serving more to highlight the questions that need to be
investigated concerning it, rather than answering all such questions.
The first way begins by noting a particular feature of the world that is evident to the
senses: the fact of motion, that some things are in motion.
The first and more manifest way is the argument from motion. It is certain, and evident to our
senses, that in the word some things are in motion.
Now whatever is in motion is moved by another, for nothing is in motion except insofar as it is in
potency to that to which it is in motion; whereas a thing moves [something else] inasmuch as it
(the mover) is in act. For to move [something] is nothing other than to educe something from
potency to act. But something cannot be reduced from potency to act, except by some being in act:
as fire makes wood, which is potentially hot, to be actually hot, and through this it moves and
alters it. But it is not possible that the same thing should be at the same time in act and in potency
in the same way, but only in different ways: for what is actually hot, cannot at the same time be
potentially hot, but it is at that same time potentially cold. It is therefore impossible that, in the
same respect and in the same way, something should be both mover and moved, or that it should
move itself. Therefore whatever is in motion must be moved by another.
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The longest portion of the text of the first way is devoted to a defense of this claim:
whatever is in motion is moved by another (omne quod movetur ab alio movetur). This thesis is
taken by St. Thomas from Aristotle’s Physics and Metaphysics, where Aristotle devotes
considerable attention to proving this claim.82 In the Latin, the repetition of the passive form
movetur could appear to render the principle tautological. However, based upon the meaning that
this principle has in the Physics and Metaphysics, and given the defense that St. Thomas offers of
the principle here, it is better rendered as “whatever is in motion is moved by another.”
The defense that St. Thomas offers of this principle (sometimes called the motor causality
principle) here depends upon an analysis of the relationship between potency and act. Motion is
defined here as the eduction of act from potency, or the reduction of potency to act.83 But
something in potency is only brought into act by something already in act: this is a general
observation about the relationship between act and potency, that the actualization of potency
requires that what actualizes already be in act. Consistent with this observation, we have seen in
every case of act-potency composition that St. Thomas urges the necessity of identifying a cause in
act responsible for the act principle.84
The question to be raised, then, is whether or not a given thing could be capable of
reducing itself from potency to act, i.e., of moving itself. St. Thomas explains that this is not
possible, because a thing cannot be in potency and in act in the same respect at the same time. He
explains this by way of example: what is only potentially hot cannot be the cause of the acquisition
of heat. For a thing to be its own first mover would require that a thing both be and not be at the
same time and in the same respect, and so it can be concluded that whatever is in motion is moved
by another.
So far, St. Thomas has argued for two claims:
(1) Certain things in the world are in motion.
(2) Whatever is in motion is moved by another.
82Indeed, within the Physics, the demonstration of the principle omne quod movetur ab alio movetur
represents the culmination of natural philosophy, as this is the final demonstration propter quid in the
Physics.
83It is important to note that this is a more general definition of motion than the definition of motion found in
the Physics.
84Insofar as the principle omne quod movetur ab alio movetur is concerned with motion, defined here as “the
reduction of potency to act,” a question to be asked is whether every instance of act-potency composition
will fall under the principle. The point I am making above is just that in every case of act-potency
composition, something actual is the cause of the act-principle in the composite.
If that by which it is put in motion be itself put in motion, then this also must be put in motion by
another, and that by another again. But this cannot go on to infinity, because then there would be
no first mover, and, consequently, no other mover; seeing that subsequent movers move only
inasmuch as they are put in motion by a first mover; as the staff moves only because it is put in
motion by the hand. Therefore it is necessary to arrive at a first mover, put in motion by no other;
and this everyone understands to be God.
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Now St. Thomas offers and defends a third claim:
(3) It is impossible to proceed to infinity in moved movers.
And then he draws his conclusion:
(4) There is some first mover that is not put in motion by anything else—and everyone
understands this to be God.
Concerning the argumentation against an infinite regress of moved movers, it is sometimes
objected that the argument seems to engage in a begging of the question, by its insistence that the
absence of a first mover is problematic. Such an objection misses that this claim is immediately
defended by St. Thomas, through this principle: subsequent movers act as movers only inasmuch
as they are moved by a first mover. To be a subsequent mover—a moved mover—is always to
depend upon a first mover in the sequence of movers. This principle does not presuppose the
conclusion of the first way, because that conclusion is that there must be a first mover, put in
motion by no other. In the example that St. Thomas uses to defend this principle, he is willing to
speak of the hand as a “first mover,” relative to the staff, but he would not say that the hand is put
in motion by no other.
Another way to put this principle then, is just this: a subsequent moved mover depends
more upon a remote mover than upon its own proximate mover for its being moved. It is the prior
mover (and ultimately the first mover) that accounts for the motion of all subsequent movers. To
deny an ultimate prior mover is therefore to deny motion in any of the subsequent movers in the
series.
Difficulties about the argument
(1) The first way suggests that a general question to be asked concerning anything that one
identifies as the first mover of a sequence of moved movers is this: is this mover put in motion by
another? Is there in it the actualization of some potency that requires the agency of a prior mover?
It is by an affirmative answer to these questions that one would be led to posit a first mover, put in
motion by no other, and it is this mover alone that St. Thomas calls God. What is not spelled out, in
the text of the first way, is an attempt at an exhaustive classification of the kinds of movers, so as
to get at the truth of the claim that it in every case the agency of a given mover that isn’t a totally
unmoved mover requires that there be a totally unmoved mover that we understand to be God.
One can respond to this objection by noting that the argument is expressed in such general
terms—with reference to act and potency—that such descent to particular details is unnecessary.
By framing the argument in terms of act and potency, what St. Thomas’s conclusion serves to
establish is the existence of something in act that is not dependent upon anything else for its being
in act.
(2) Another difficulty is that it does not seem to be obvious that a first mover, put in
motion by no other, must be God. This difficulty dovetails with the first, insofar as one might think
that even an unmoved first mover could be, e.g., a soul or a formal cause.
To the degree that one finds this objection compelling, one can regard the conclusion of the
first way—“and this everyone understands to be God”—as a sort of promissory note rather than a
demonstrated conclusion. That is, a first mover put in motion by no other might not obviously be
God, but subsequent argumentation about the characteristics of the first mover will include
Carl: Metaphysics 104
characteristics understood to be exclusive and proper to God alone: absolute simplicity, perfection,
infinity, eternity, etc. If it seems too hasty to assert that a first mover must be God, then this is a
difficulty only to be settled by subsequent argumentation. Nevertheless, in looking back upon the
first way (after that subsequent argumentation), one could then recognize that it was God’s
existence that was demonstrated.
Is this an argument in physics or metaphysics?
Owing to the fact that the first way is an argument from the fact that there are beings in
motion, no small number of commentators have thought that the first way must therefore belong
properly to physics (the subject of which is mobile being) rather than to metaphysics. Against such
a suggestion, I would note two things: (1) The meaning of motus in the principle omne quod
movetur ab alio movetur is exceptionally broad for St. Thomas, as evidenced by the fact that later
in the Summa theologiae, he includes the operations of the human will as falling under the
principle (and he references the first way for proof of this principle). (2) Unlike other ways of
arguing for the principle omne quod movetur ab alio movetur which are properly physical (and
which St. Thomas does employ in his presentation of the argument from motion in the Summa
contra Gentiles), by relying upon an analysis of the relationship between act and potency, St.
Thomas argues for this principle in particular in a manner more appropriate to metaphysics than to
physics: as we have noted before, act and potency themselves belong to the subject-matter of
metaphysics, as two of the features attending ens commune.
Carl: Metaphysics 105
13. Divine Simplicity: God as Ipsum Esse
Following the demonstration of God’s existence, St. Thomas proceeds to a consideration of
what other truths can be known concerning God besides the fact of His existence. The first truths
that St. Thomas demonstrates concerning God, both in the Summa contra Gentiles and in the
Summa theologiae, fall under the heading of what is called the divine simplicity, that is, the denial
of any composition in God.
13.1. How Truths Beyond God’s Existence Can Be Known: the Via Remotionis
As affirmed above, St. Thomas denies the possibility of any quidditative knowledge of
God in this life: it is impossible for human being’s to know the essence of God, to know what God
is in Himself, in this life. As St. Thomas has explained, from God’s effects one can only know that
He exists, not what He is.
If this were the last thing to be said concerning the knowledge of God possible according
to natural reason, then we would face the difficulty that one could not argue from natural reason
against someone who, for example, denied that God is one, that God is intelligent, that God is
powerful, that God is loving, etc. As we will shall see, St. Thomas does consider such truths to be
demonstrable by natural reason (that is, by reason not directly aided by revelation). We should
comment now on how St. Thomas thinks that this can be the case.
The via remotionis
In Summa contra Gentiles I c. 14, St. Thomas notes that, by the end of c. 13, the existence
of God as the First Being has been established. Having established the existence of God, it is now
appropriate to investigate His properties or conditions (eius conditiones). St. Thomas then asserts
that in order to accomplish this, it will be most appropriate to make use of the way of remotion (via
remotionis), also sometimes called the via negativa or negative way.
That in this life we cannot know what God is does not mean that we are unable to know
what God is not. Indeed, knowing what God is not is extremely valuable as a way of knowing Him.
St. Thomas explains:
Now, in considering the divine substance, we should especially make use of the method of
remotion. For, by its immensity, the divine substance surpasses every form that our intellect
reaches. Thus we are unable to apprehend it by knowing what it is. Yet we are able to have some
knowledge of it by knowing what it is not.
Furthermore, we approach nearer to a knowledge of God according as through our intellect we are
able to remove more and more things from Him. For we know each thing more perfectly the more
fully we see its differences from other things; for each thing has within itself its own being, distinct
from all other things. So, too, in the case of the things whose definitions we know. We locate them
in a genus, through which we know in a general way what they are. Then we add differences to
each thing, by which it may be distinguished from other things. In this way, a complete knowledge
of a substance is built up.
Carl: Metaphysics 106
Although we are not capable of knowing what God is, nevertheless we are capable of
distinguishing God from other things by noting the things that God is not. Indeed, as we indicated
at the beginning of our course, even the positive knowledge of an essence or quiddity always also
involves coming to know the thing in question as distinct from all other things: this is why even the
positive knowledge of the essence of a corporeal substance is expressed through a genus and
difference, in which the thing is divided from every other member of the genus.85 One thus grasps
only in a general way what a thing is, and then proceeds to differentiate it from other members of
its genus.
In other words, there is a negative element even in the quidditative knowledge of a finite
substance. Therefore, it should not be a surprise that even though quidditative knowledge is not
possible concerning God, nevertheless a broadly similar negative knowledge—a knowledge of
what God is not—will still be possible. However, St. Thomas adds some important qualifications
concerning this negative approach to knowledge of God:
St. Thomas notes that unlike the knowledge of the quiddity of a corporeal substance, we
cannot begin our examination of God by placing Him in any genus: even the statement of a thing’s
genus is already a grasp of what the thing is. Nor will we distinguish God from other things by
affirming a difference: every difference is a positive characteristic (e.g., rationality). A difference
serves to distinguish a quiddity from other quiddities in the same genus, but it does so insofar as it
is a positive characteristic possessed by the quiddity. A difference adds to the genus, and this is
why it must be taken from outside the genus.
85We cited the following text from SCG 3.46: “But through knowing about a thing what it is, the thing is
known just as it is distinct from other things: therefore also a definition, which signifies what a thing is,
distinguishes the definitum from all other things.”
However, in the consideration of the divine substance we cannot take a what as a genus; nor can
we derive the distinction of God from things by differences affirmed of God.
For this reason, we must derive the distinction of God from other beings by means of negative
differences. And just as among affirmative differences one contracts the other, so one negative
difference is contracted by another that makes it to differ from many beings. For example, if we
say that God is not an accident, we thereby distinguish Him from all accidents. Then, if we add that
He is not a body, we shall further distinguish Him from certain substances. And thus, proceeding in
order, by such negations God will be distinguished from all that He is not. Finally, there will then
be a proper consideration of God’s substance when He will be known as distinct from all things.
Yet, this knowledge will not be perfect, since it will not tell us what God is in Himself.
Carl: Metaphysics 107
Therefore, one does not distinguish God from other beings by affirmative differences, but
by negative differences. St. Thomas then compares affirmative differences and negative
differences, by first noting that affirmative differences contract one another: for example,
corporeality (the difference of body as a species of substance) is itself further contracted by life
(the difference of living things), which is in turn further contracted by sensitivity (the difference of
animal), which is further contracted by rationality (the difference of man). Negative differences, in
a similar fashion, can serve to distinguish a thing from more and more things; in this way negative
differences too contract one another, as the thing being distinguished by negative differences has
more and more things removed from it. It is for this reason that the procedure of knowing God
through such negative differences is called the way of remotion: one removes from God all those
things that He is not, so as to come to a proper consideration of God’s substance as distinct from all
things. Nevertheless, this proper consideration of God as distinct from all things (ut ab omnibus
distinctus) is not a knowledge of what God is in Himself.
St. Thomas concludes SCG I c. 14 by announcing that he will take what was established in
the argument from motion as a starting point in the way of remotion: this is the proposition that
God is absolutely unmoved. As the order of the divine attributes unfolds in the Summa contra
Gentiles, everything said about God ultimately depends upon this claim that God is unmoved in
every way.
The Summa theologiae on how God’s attributes are known
The text in the Summa theologiae that parallels Summa contra Gentiles I c. 14 differs
somewhat in emphasis, and it is worth it to examine this text briefly before proceeding to our
examination of St. Thomas’s actual arguments for the divine attributes. This parallel text is Summa
theologiae q. 3 pr.:
It being known of something whether it is, it remains to be inquired how it is, so that it may be
known about it what it is. But since of God we cannot know what He is, but [only] what He is not,
we cannot consider about God how He is, but rather how He is not. First therefore how He is not
will be considered; second how He may be known by us; third, how He may be named.
But it can be shown about God how He is not, by removing from Him those things which do not
belong to Him, such as composition, motion, and others of this kind. First therefore we will inquire
about His simplicity, through which composition is removed from Him. . .
Carl: Metaphysics 108
Whereas the text from the Summa contra Gentiles emphasizes that by the way of remotion
we remove from God what He is not, in this text from the Summa theologiae instead St. Thomas
says that we remove those things that concern how He is not. What does St. Thomas mean by how
(quomodo) something is, as distinguished from what (quid) it is? Given what he says here, it would
seem that quomodo sit is the question that is asked concerning a subject of study, once its existence
has been shown but before its quiddity is known: that is, answering the question quomodo sit is
what a science does in the stage in between knowing whether its subject exists (an sit) and its
reaching conclusions about the definition of its subject (quid sit). This suggestions seems to be
confirmed by a brief text from the Commentary on the Physics, in which St. Thomas notes that “it
pertains to natural [philosophy] to determine about the infinite, if it is or if it is not, and how it is,
and what it is. . .”86 Here the question quomodo sit is inserted in between the questions an sit and
quid sit.
When St. Thomas says, therefore, that we cannot know how God is, because we cannot
know what He is, he means that it is the knowledge of how something is—its mode of being—that
allows one to arrive at knowledge of what it is (and thus how it is positively distinguished from all
other things). Because we cannot know what God is, therefore neither can we know how God is.
Therefore, instead of saying what God is not, St. Thomas proceeds in the Summa theologiae by
explaining how God is not, that is, by removing those modes of being that are unfitting. This
begins with the removal of every mode of composition, i.e., the assertion of the divine simplicity,
to which we now turn.
13.2. Establishing Divine Simplicity
St. Thomas treats the divine simplicity in detail in both Summa contra Gentiles I cc. 16-27
and in Summa theologiae I q. 3. We will base the following discussion on the latter texts, and we
will summarize many of St. Thomas’s arguments.
a. 1: God is not a body
St. Thomas begins by removing from God the corporeal mode of existence, arguing that
God cannot be a body because:
(1) No body is a mover unless it is itself in motion.87 But God is an unmoved mover.
Therefore, God is not a body.
-This argument depends upon a thesis taken from Aristotle’s Physics, that whenever a body
is a mover it must also be something in motion.
(2) The first being must be in act and in no way in potency, since act absolutely precedes
potency (because whatever is in potency is reduced to act only by some being in act). But God is
the first being. Therefore God is without any potency and is pure act. But every body is in potency
to something. Therefore God is not a body.
-Although St. Thomas’s announced purpose is just to argue that God is not a body, he
accomplishes this by arguing for something more radical and fundamental, that God is pure act
with absolutely no potency. This claim will have important implications as St. Thomas’s arguments
concerning the divine attributes unfold.
86In Libros Physicorum Bk. 4, lec. 1.
87St. Thomas says that this is clear by induction through singulars. It is also a thesis asserted by Aristotle in
Book III of the Physics.
Carl: Metaphysics 109
a. 2: God is not composed of matter and form
At issue in a. 2 is the question of whether or not God might be composed of matter and
form, despite the fact that He is not a body. This might seem to be an unnecessary question, but no
small number of medieval theologians thought that some incorporeal realities—angels—are
composed of matter and form: not corporeal matter, but spiritual matter.
St. Thomas argues elsewhere (such as in the De ente et essentia) against such a view, by
observing that corporeal matter is not of itself intelligible to the human intellect: it is form that is
the principle of intelligibility, because everything is known according to formal likeness. If one
distinguishes prime matter as a genus into corporeal matter and spiritual matter, then one must say
that the substantial form that makes corporeal matter to be corporeal matter is itself the principle of
the unintelligibility of corporeal mattter: but it is absurd to suggest that a form could be a principle
of unintelligibility.
Concerning whether or not God could be a composite of matter and form, St. Thomas
argues in q. 3 a. 2 that this is impossible, because God is pure act, whereas matter is a principle of
potency. The main argument establishing the lack of matter-form composition in God in a. 2 is
therefore what was demonstrated in a. 1, that God is pure act with absolutely no potency.
a. 3: God is the same as His essence
In corporeal substances, which are individual instances of universal essential kinds, there
is always a distinction between the individual and its essence. That is, Socrates is a man, but he is
not humanity. The question considered in a. 3 is whether there is a similar distinction to be drawn
between God and His essence?
St. Thomas answers this question by explaining that in corporeal substances, the reason for
the distinction between the individual (suppositum) and its essence is the matter-form composition
of these substances. Humanity and a man are not absolutely identical, because the man has
particular matter that is not included in the abstract essence, humanity. Because in any incorporeal
substance there is no matter-form composition, St. Thomas argues that suppositum and essence or
nature will be identical. He concludes: “And thus, since God is not composed of matter and form,
as was shown, it must be that God is His deity, His life, and whatever else is thus predicated of
Him.” It should be noted that this conclusion—the identity of suppositum and essence—applies
also to angels.88
a. 4: in God essence and esse are identical
We now proceed to a consideration of one of the most famous texts of the Summa
theologiae: I q. 3 a. 4, in which St. Thomas argues for the identity of essence and esse in God. He
offers three arguments for this conclusion; we will consider the first two, leaving aside the third
because of its dependence upon the notion of participation, which we have not treated in this
course.
(1) Whatever a thing has besides its essence must be caused either by the principles of that
essence (e.g., in the way that properties are caused by essence) or by some exterior agent (as heat is
caused in water by fire). Therefore if a thing’s esse differs from its essence, then this esse must be
caused, either by some extrinsic agent or by the essence of the thing. It is impossible, however, for
anything’s esse to be caused by its essence, because in such a case a thing would be the sufficient
cause of its own existence, which is absurd. Therefore, anything whose essence differs from its
88However, there is some controversy about whether St. Thomas later changed his mind about this claim as it
applies to angels. See Wippel 243-53.
Carl: Metaphysics 110
esse must have its esse caused by an extrinsic agent. But this cannot be true of God, because God is
the first efficient cause.
-If essence and esse are distinct in any given thing, then the esse must be caused, either by
the essence or by an extrinsic agent; but it is impossible for a thing’s essence to be the cause of its
own esse, because then the thing would be a sufficient self-cause with regard to its existence,
which cannot be admitted. Therefore God’s essence cannot be the cause of His esse. This leaves
only the possibility that God’s esse is caused by some other agent. But God is the first efficient
cause and is totally uncaused—this was established by St. Thomas in his second way of arguing for
God’s existence. Therefore, in God, essence and esse must be identical.
(2) Esse is the actuality of every form or nature: for example, goodness and humanity are
not signified in act, except insofar as we signify them to be (esse). Therefore esse must be
compared to essence, if the latter is distinct from the former, as act to potency. But in God there is
no potency, because He is pure act, and so in Him esse and essence cannot differ.
-Once again we find that the claim that God is pure act is used to establish a further claim
about the divine simplicity. Because essence-esse composition is an instance of potency-act
composition, it cannot be the case that in God there is a composition of essence and esse, and
therefore in Him essence and esse are the same.
a. 5: God is not in a genus
Having established the identity of essence and esse in God, St. Thomas proceeds in a. 5 to
argue that God is not in a genus. St. Thomas begins by distinguishing between two different ways
in which a thing can be said to be in a genus:
(a) by being contained under that genus as a species
(b) by being the principle of the genus (e.g., this is how a point is in the genus of
continuous quantity, by being the principle of extension, even though a point is not itself something
having extension) –we will leave behind specific commentary on St. Thomas’s brief argument
against this possibility
Regarding the first possibility, being contained under a genus as a species, St. Thomas
offers three arguments:
(1) Every species in a genus is constituted by the genus plus a difference. By this
composition, the relationship of the difference to the genus is a relationship of act to potency. But
God is pure act without potency, and so He cannot be contained in a genus as a species.
(2) In God essence and esse are identical. If therefore He were in a genus, His genus would
have to be ens, since the genus signifies the essence of a thing. But ens cannot be a genus, for the
reasons given by Aristotle. Therefore God is not in a genus.
(3) Everything in a given genus agrees or shares in the essence of the genus that is
predicated of them to express what they are. However, these things sharing a genus also differ in
esse from one another. Therefore in every member of a genus, esse and quiddity or essence must
differ.89 But in God essence and esse do not differ. Therefore God is not in a genus as a species.
That God is not contained in a genus has two important implications: (1) It is absolutely
impossible to offer a definition of God, because a definition is given by naming the genus and
specific difference of a thing. (2) God shares nothing in common univocally with any creature,
because every creature is in a genus. We will comment more on this latter claim later, in our
89This is an instance of what is typically called the genus argument for real distinction of essence and esse.
Carl: Metaphysics 111
discussion of the “transcendental” analogy between God and creatures.
a. 6: in God there are no accidents
Next, in a. 6, St. Thomas argues that there is no substance-accident composition in God.
We will briefly note only his first argument:
(1) A subject of accidents is related to its accidents by a relationship of potency to act. But
God is pure act without potency, and therefore He cannot have any accidents.
-Again, we find St. Thomas arguing for a kind of simplicity in God from His being pure
act without potency. There can be no substance-accident composition in God because God is pure
act.
a. 7: God is simple in every way (omnino simplex)
Summarizing and generalizing the conclusions reached in q. 3, in a. 7 St. Thomas
concludes that God is in every way simple. His first argument for this conclusion is just from the
previous articles of q. 3: he summarizes the various modes of composition or complexity that have
been excluded from God.
(1) God has no composition of quantitative parts, because He is not a body.
(2) God has no matter-form composition.
(3) There is in God no distinction between nature and suppositum.
(4) God has no essence-esse composition.
(5) God has no composition of genus and difference.
(6) God has no subject-accident composition.
St. Thomas concludes from this list that God is in every way simple. The form of argument
employed here is induction, which is valid so long as St. Thomas has provided an exhaustive or
complete list of the possible ways in which a thing can be composite. These are indeed all of the
modes of composition found in beings under ens commune, and so St. Thomas’s argument is valid.
St. Thomas then adds several other arguments for the absolute simplicity of God, which we
need not consider at this time.
a. 8: God does not enter into composition with other things
So far, it has been established that there is no composition in God himself: He is absolutely
simple, with none of the modes of composition found in creatures present in Him. But it could be
suggested that even though God is not Himself composite, perhaps He enters into composition with
other things: just as a substantial form is in itself something simple, but it nevertheless enters into
composition with prime matter.
St. Thomas notes that there have been three erroneous views connected with this
suggestion:
(a) That God is the world-soul or the soul of the outermost heavenly sphere.
(b) That God is the formal principles of all things
(c) That God is prime matter, which was “most foolishly” posited by David of Dinant.
St. Thomas then offers three arguments against any such view that God is composite with
other things. We will note only the first, which proceeds from the claim that God is an efficient
cause.
(1) Because God is the first efficient cause (as was established by the second way), He is
not the intrinsic formal cause of anything that He causes: for an efficient cause can only of the
same form specifically as the form that it causes, not numerically. Furthermore, because He is the
first efficient cause, He cannot be prime matter, which is pure potency.
Carl: Metaphysics 112
Final comments on divine simplicity
We have carefully attended to the contents of Summa theologiae I q. 3 concerning the
divine simplicity. It is important to emphasize that in itself the doctrine of divine simplicity is that
in God there is not any kind of composition whatsoever. This doctrine can be “broken down,” as it
were, according to the various kinds of composition that are found in finite beings but not in God.
It is helpful to state clearly what the doctrine of the divine simplicity is, according to St.
Thomas, because no small number of recent authors, many of them even commenting on the
thought of St. Thomas, have taken the primary meaning of divine simplicity to be the following:
that all of God’s attributes are in reality identical, so that His power is His wisdom, which is also
His esse, which is also His goodness, etc. While these claims are true (something to which St.
Thomas alludes in q. 3 a. 3), this is nevertheless not the primary meaning of simplicity: simplicity
means the absence of composition.
13.3. A Brief Metaphysics of Creation
Before proceeding to a consideration of other divine attributes, we should make some brief
remarks about the notion of creation as St. Thomas understands it. Already within q. 3, St. Thomas
has offered arguments for (a) the identity of essence and esse in God and (b) the real distinction of
essence and esse in all other things. Because in any being in which essence and esse are distinct,
esse must be caused by something extrinsic agent, God must at a minimum be the ultimate efficient
cause of all existing things. The activity according to which God causes things to exist is called
creation. We will very briefly summarize some important Thomistic claims concerning creation.
(1) In Summa theologiae I q. 45 a. 1, St. Thomas asserts that by creation he means the
emanation of all beings (those under ens commune) from subsistent esse, that is, from God.
(2) In a. 5 of this same question, St. Thomas explains that only God has the power to
create, and it is impossible for God to communicate the power to create to any creature.
(3) In a. 2 of the same question, St. Thomas explains that creation insofar as it is something
in creatures, is the relation of dependence that the creature has with respect to God. Every creature
is related to God as something caused to its efficient cause. This relation is a real relation between
creatures and God, but there is not any corresponding real relation from God to creatures.
(4) St. Thomas sharply distinguishes between creation and generation (that is, substantial
change that produces a new substance). Generation presupposes pre-existing prime matter, which
is the subject of substantial change. But God creates ex nihilo, presupposing absolutely no subject.
For this reason, it would be a most serious mistake to think of creation as presupposing essences as
already-existing things that receive esse from God. When we say that God causes esse, we do not
mean to exclude that God also causes a thing’s essence: indeed, God must cause both a thing’s esse
and its essence. Or, to put it more simply, what God causes to exist are the individuals of various
essential kinds. God does not create just esse or essences, but essence-esse composites, i.e., beings.
(5) Creation is not a “one-time” event in the past or at the beginning of the existence of a
given thing. Rather, God continually causes things to exist, sustaining all creatures in existence. If
God did not do this, then creatures would immediately cease to exist.
Carl: Metaphysics 113
14. Divine Perfection
In Summa theologiae I q. 4 and 6, St. Thomas treats the divine perfection and the divine
goodness.
a. 1: God is perfect
St. Thomas’s argument for the perfection of God in q. 4 a. 1 is stated very briefly. He notes
that some ancient thinkers did not attribute perfection to the first principle of the universe, because
they thought that the first principle was something material, which is necessarily imperfect.
However, St. Thomas asserts that the first principle, God, is not a first principle as a material cause
(which was the most foolish opinion expressed by David of Dinant), but rather as an efficient
cause, and therefore God must be most perfect. St. Thomas explains that an agent, as such, is
always in act; therefore the first agent must be most actual. But perfection is according to a thing’s
degree of actuality, and therefore God, being pure and total actuality, must be most perfect.
The notion of perfection employed here is this: to be perfect is to lack nothing of the mode
of perfection appropriate to a thing. Because God is pure act and is without any potency, it cannot
be the case that He is imperfect, i.e., that He lacks anything appropriate to Himself. Therefore, He
must be perfect.
It is absolutely essential to note that the notion of perfection expressed here is a quasinegative notion: to be perfect is not to lack any actualization that is appropriate to a thing’s mode of
perfection. As Msgr. Wippel analyzes the argumentation for divine perfection, it represents a
crucial turning point in the via negativa: the via negativa arrives at a kind of double negation when
it denies the lack of any appropriate perfection to God.90 Perfection is a negative name with, as it
were, positive implications, as we will see in the following article.
a. 2: the perfections of all things are in God
Perfection as St. Thomas argues for it in a. 1 is a negative name. In a. 2, St. Thomas draws
from this negative name some positive implications, in arguing that God is universally perfect so
as not to lack any excellence found in any genus. He argues for this in two ways:
(1) Whatever perfection exists in an effect must be found in its efficient cause, either
according to the same form (if the cause is a univocal agent) or in a more eminent degree (if the
cause is an equivocal agent). Now, whereas to pre-exist in a material cause (that is, in the principle
of potency) is to exist in a less perfect way than the effect, to pre-exist in an efficient cause is to
exist in a more perfect way. For example, the dog that is capable of causing another dog to exist is
more perfect than the dog that initially comes to exist as an effect. Therefore, because God is the
first efficient cause of everything that exists, all of the perfections of things must pre-exist in Him.
However, He is not a univocal agent, because He does not share a genus with any creature; and
therefore all perfections of creatures must pre-exist in God in a more eminent way.
-By a univocal agent, St. Thomas means an efficient cause that shares in the same species
as its effect. For example, a man causes a man through reproduction, and fire causes fire. By an
equivocal agent, St. Thomas means a higher agent that produces an effect despite not sharing in the
same species. For example, he thinks that the sun is an equivocal cause of heat: that is, he thinks
that the sun is not actually hot in the same way that things in the sublunary are hot.
(2) God is ipsum esse per se subsistens: existence itself subsisting per se. Therefore, He
must contain within Himself the entire perfection of being, just as if there were some separate,
90See Wippel 517, 529.
Carl: Metaphysics 114
subsisting heat, it would necessarily lack nothing of the entire virtue of heat. But every created
perfection is included in the perfection of being, because anything is perfect just insofar as it has
esse in some mode. That is, every perfection is a mode of esse. The being that is subsistent esse
itself therefore cannot lack the perfection of any thing.
-From the identity of essence and esse in God, St. Thomas argues that God cannot lack any
of the perfections of created things, because every perfection is just a mode of esse.
a. 3: that creatures are like God
Finally, St. Thomas argues in a. 3 that creatures possess a likeness to God, not according to
univocal agreement in some form in the same mode, but according to a diminished sharing in a
formality that is analogically common. This is the foundation of his later elaboration on the
analogical character of all divine naming.
In articulating this, St. Thomas offers a division of the ways in which one thing can be like
another:
(1) Some things are alike because they share in the same form according to the same ratio
and in the same mode. Such things are not only alike, but equal. For example, two things of equal
whiteness are equally alike in whiteness. This is the most perfect form of likeness.
(2) Some things are alike insofar as they share in a form according to the same ratio, but
not in the same mode or measure. For example, two things can both be white, but one is more
white than the other. This is an imperfect likeness.
(3) Some things are alike insofar as they share in the same form, but not according to the
same ratio. This occurs in the relationship between a univocal cause and its effect.
At this point, St. Thomas introduces two crucial axiomatic claims:
(a) Every agent produces something like itself: omne agens agit sibi simile.
(b) Everything acts according to its form: unumquodque agit secundum suam formam
From these principles St. Thomas concludes:
As we shall see in subsequent discussion of the names of God and of the analogy of being
between God and creatures, this principle that omne agens agit sibi simile is absolutely crucial. It is
because every agent produces something like itself that there will be an analogical likeness
between creatures and God.
Therefore if there is an agent not contained in any genus, its effect will even more distantly
reproduce the form of the agent, not, that is, so as to participate in the likeness of the agent’s form
according to the same specific or generic ratio, but only according to some sort of analogy; as esse
is common to all. In this way all created things, insofar as they are beings, are like God as the first
and universal principle of all being.
Carl: Metaphysics 115
15. Divine Naming: the Threefold Way
Having established the various divine attributes treated in Ia qq. 3-11, St. Thomas proceeds
in qq. 12-13 to a discussion of how God is known by us and how God is named. Since we have
already treated in part the question how God can be known by us—as a cause is known, albeit
imperfectly, from its effects—we will here only attend to some points we haven’t yet emphasized.
15.1. The Impossibility that a Creature Should Comprehend God
No creature can see the essence of God by its own natural power
No creature seeing the essence of God can comprehend Him
15.2. The Threefold Way of Knowing and Naming God
The triplex via
Res significata and modus significandi
Carl: Metaphysics 116
16. Analogy II: the “Transcendental” Analogy and the Divine Names
The doctrine of analogy in St. Thomas is most famously applied on what we earlier called
the “transcendental” level, that is, between God and creatures. We will now proceed to a
consideration of the notion of analogy between God and creatures, particularly with regard to the
analogical character of being.
With regard to the analogy between God and creatures, the thought of St. Thomas appears
to have undergone some development and modification over the course of his writing career.91 In
brief, we can trace two significant developments:92
(1) From a primary formulation of analogy early in his career as four-term proportionality
to a later primary formulation of analogy as the relation of one thing to another. We will examine
this development by comparing a text from the early De veritate with a couple of texts from later
in St. Thomas’s career.
(2) From an earlier emphasis on the exemplar formal causality of the divine essence to a
later emphasis on the efficient causality of God, with the consequent likeness between creatures
and God. This development can be helpfully examined by comparing a text from the Commentary
on the Sentences with some texts from after the period of the Summa contra Gentiles.
16.1. Analogy as Proportion(ality) and Analogy as a Relation of One to Another
Analogy as Proportionality: De veritate q. 2 a. 11
De veritate q. 2 a. 11 asks whether or not knowledge (scientia) is predicated equivocally or
univocally of God and of creatures.93 St. Thomas denies that there could be any univocal
predication of such a term with respect to God and creatures. Univocal predication occurs when the
same term is predicated of two realities according to exactly the same ratio: but because creatures
only imperfectly imitate the divine essence, it cannot be the case that their perfections—including
knowledge—could equal the perfections of God that they imitate. Therefore the perfections of
creatures and the perfection of God must be understood according to diverse rationes.
However, St. Thomas argues that such terms that are truly predicated of both God and
creatures cannot be predicated in a purely equivocal way. If there were not some likeness between
creatures and God, then God could not know creatures by knowing Himself (St. Thomas has
already established that God does know creatures in just this way earlier in q. 2). Furthermore, if
terms predicated of both creatures and God were all purely equivocal, then it would be impossible
to reason from creatures so as to arrive at some knowledge of God. Finally, if terms were purely
equivocal between God and creatures, we would not have any basis upon which to know in any
way the ratio of these terms as they are applied to God; and therefore, any name could be as
fittingly predicated of God as well as any other, which is absurd.94
St. Thomas concludes that therefore scientia must be predicated neither entirely univocally
91In my view, perhaps the single best treatment of the analogy of being, particularly on the transcendental
level, is that found in Bernard Montagnes’ The Doctrine of the Analogy of Being according to Thomas
Aquinas, tr. E. M. Macierowski (Milwaukee: Marquette, 2004). The historical developments noted in
these notes are dealt with at length in this book, as well as in Wippel 543-72.
92However, it must be noted that these are generalizations, and the issue is considerably more complicated
than this brief summary suggests.
93See Wippel 550-55.
94See Wippel 551 for his summary of these arguments.
Carl: Metaphysics 117
nor purely equivocally of God’s scientia and of ours. Instead, this term is predicated analogously:
St. Thomas here distinguishes between a two-term proportion, in which there is some
determinate relation between the two terms of the relation, and a four-term proportionality, in
which there is an agreement not in a determinate way between two things, but rather between two
proportions. The former case—proportion—is how two is related to one as double. The latter
case—proportionality—is how the relation of four and two is in agreement with the relation of six
and three or of twenty and ten.
St. Thomas then proceeds to note that the first kind of analogy of proportion occurs in the
analogical predication of the term being with respect to accidents and substance: “Being is
predicated of substance and accident because of the relation which accident has to substance.” This
is what we have previously called the horizontal analogy of the categories, and in the terminology
of De veritate q. 2 a. 11, the horizontal analogy is an analogy of proportion. The determinate
relation that exists between an accident and a substance is that the former inheres in the latter as in
its subject cause.
He now reaffirms that wherever terms are predicated analogously according to proportion,
there must be some determinate relation (aliquam determinatam habitudinem) between those
Instead it is predicated analogously, or, in other words, according to a proportion (secundum
proportionem). Since an agreement according to proportion can happen in two ways, two kinds of
community can be noted in analogy. There is a certain agreement between things having a
proportion to each other from the fact that they have a determinate distance between each other or
some other relation to each other, like the proportion which the number two has to unity in as far as
it is the double of unity. Again, the agreement is occasionally noted not between two things which
have a proportion between them, but rather between two related proportions—for example, six has
something in common with four because six is two times three, just as four is two times two. The
first type of agreement is one of proportion (proportionis); the second, of proportionality
(proportionalitatis).
those terms predicated according to the first type of analogy, there must be some definite
relation between the things having something in common analogously. Consequently, nothing can
be predicated analogously of God and creature according to this type of analogy; for no creature
has such a relation to God that it could determine the divine perfection.
Carl: Metaphysics 118
things in which there is something in common by analogy. He argues from this to the following
conclusion. Having distinguished between analogy as two-term proportion and as four-term
proportionality, St. Thomas excludes the first type of analogy as regards the common predication
of terms with respect to God and creatures. Concerning the second type of analogy, proportionality,
he continues:
St. Thomas thus allows the possibility that a term might be predicated of both God and
creatures according to analogy, but only according to an analogy of four-term proportionality. He
continues:
St. Thomas distinguishes here between metaphorical names and names that can be
properly predicated of God. What distinguishes the former names is that the very definition of a
metaphorical name there is included matter: that is, any name of the essence of something
corporeal cannot be predicated of God except metaphorically. But where a name’s definition
contains no matter, it will be possible to find between God and creatures an agreement of the
second kind indicated above, that is, of four-term proportionality.
Unfortunately, St. Thomas only gives examples of names that can be predicated
analogously—being, good, etc.—without carefully spelling out the nature of the proportionality.
He seems to mean something like this: the being of a creature is related to its goodness as the
being of God is related to His goodness. This interpretation seems confirmed by what St. Thomas
asserts in De veritate q. 23 a. 7 ad 9:
But in the other type of analogy, no definite relation is involved between the things which have
something in common analogously, so there is no reason why some name cannot be predicated
analogously of God and creatures in this manner.
this can happen in two ways. Sometimes the name implies something belonging to the thing
primarily designated which cannot be common to God and creature even in the manner described
bove. This would be true, for example, of anything predicated of God metaphorically, as when
God is called lion, sun, and the like, because their definition includes matter which cannot be
attributed to God. At other times, however, a term predicated of God and creature implies nothing
in its principal meaning which would prevent our finding between a creature and God an
agreement of the type described above. To this kind belong all attributes which include no defect
nor depend on matter for their act of existence, for example, being, the good, and similar things.
Carl: Metaphysics 119
Curiously, in this text, St. Thomas first raises the possibility that there can be a direct
proportion between creature and God, according to any of the relations that can be said to exist
between creature and God—for example, the dependence relation of creation. However, he
qualifies that this is an extended sense of the term proportion, rather than its proper meaning. He
then proceeds to explain, as an alternative solution to the objection, the way in which there can be
a proper proportionality between creatures and God: as a creature stands to what is its own, so God
stands to those things which belong to Him. This implies that our suggestion above was correct:
Because man is infinitely distant from God, there cannot be a proportion between him and God in
the proper sense of proportion as found among quantities, consisting of certain measure of two
quantities compared to each other. Nevertheless, in the sense in which the term proportion is
transferred to signify any relationship of one thing to another. . ., nothing prevents our saying that
there is a proportion of man to God, since man stands in a certain relationship to Him inasmuch as
He is made by God and subject to Him.
Or the answer could be given that although there cannot be between the finite and the infinite a
proportion properly so called, yet there can be a proportionality or the likeness of two
proportions. . . . Although the finite and the infinite cannot be proportioned, they can be
proportionable, because the finite is equal to the finite just as the infinite is to the infinite. In this
way there is a likeness of the creature to God, because the creature stands to the things which are
its own as God does to those which belong to Him.
Carl: Metaphysics 120
the analogy between creatures and God means that as creaturely being is to creaturely goodness (or
creaturely truth, or creaturely scientia), so is the divine being to the divine goodness (or truth or
scientia), etc.
Having suggested this four-term proportionality as what is meant by the analogy between
creatures and God in the De veritate (and having rejected analogy of proportion), St. Thomas
seems to have almost immediately abandoned this suggestion, as it does not appear in any of his
later writings.95 Even by the time that he finished the De veritate, he has backed off from the strong
claim that no proportion is possible between creatures and God, instead saying that there is
proportion, but just not in the strict sense of mathematical proportion. I would offer the suggestion
(following Montagnes’ account of the development in St. Thomas’s thinking) that the theory of
four-term proportionality was not St. Thomas’s definitive solution to the question of the analogy
between creatures and God. It was instead a solution that he advanced in an early writing, but later
abandoned. We will now turn to a consideration of what replaced the four-term proportionality as
St. Thomas’s account of the analogical character of the divine names.
Summa contra Gentiles cc. 32-34
We will now consider texts from a later writing, the Summa contra Gentiles I cc. 32-34. As
in the De veritate, St. Thomas begins by excluding both totally univocal and purely equivocal
predication of names with regard to God and creatures.96 Two points concerning the arguments
against univocal predication and equivocal predication should be made:
(1) The final argument offered against univocal predication in c. 32 introduces some
important language.
95There are some texts where analogy understood as four-term proportionality is mentioned, but this kind of
analogy is not applied to the common predication of terms with respect to God and creatures.
96See Wippel 555-60 for his careful analysis of the arguments in cc. 32 and 33.
Then, too, what is predicated of some things according to priority and posteriority is certainly not
predicated univocally. For the prior is included in the definition of the posterior, as substance is included
in the definition of accident according as an accident is a being. If, then, being were said univocally of
substance and accident, substance would have to be included in the definition of being in so far as being
is predicated of substance. But this is clearly impossible. Now nothing is predicated of God and creatures
as though they were in the same order, but, rather, according to priority and posteriority. For all things
are predicated of God essentially. For God is called being as being entity itself, and He is called good as
being goodness itself. But in other beings predications are made by participation, as Socrates is said to
be a man, not because he is humanity itself, but because he possesses humanity. It is impossible, therefore,
that anything be predicated univocally of God and other things.
Carl: Metaphysics 121
St. Thomas indicates that nothing that is said “according to priority and posteriority” is
predicated univocally. He gives the example of substance and accident, saying that being is
predicated primarily of substance and secondarily of accident, because accident depends upon
substance and contains substance within its own ratio or definition. Similarly, he says, being and
goodness are predicated of God essentially, because He is ipsum esse and goodness itself; but other
beings are beings and goods by participation. Therefore these terms are not said univocally of God
and creatures. The point to be noted here is that St. Thomas draws a direct comparison between the
horizontal analogy and the transcendental analogy: both are instances of predication “according to
priority and posteriority.” It will be important to recall this later.
(2) In the arguments against purely equivocal predication in c. 33, there is an emphasis on
the relation and likeness that must exist between creatures and God.
Relation:
In this first argument, he says that in purely equivocal predication, “there is no order or
reference of one to another, but it is entirely accidental that one name is applied to diverse things.”
This cannot be admitted in the predication of terms with regard to both God and creatures, because
“we note in the community of such names the order of cause and effect.” That is, there is a relation
of creatures to God, the relation of an effect to the cause, and it is this relation that excludes purely
equivocal predication.
Likeness:
St. Thomas in this next argument says that purely equivocal predication excludes a
likeness between the things named (or at least any likeness having anything to do with the common
name). But creatures are like God (as St. Thomas had proven earlier in the discussion of divine
perfection, just as he does later in the Summa theologiae I q. 4 a. 3). Therefore pure equivocation
can be ruled out.
For in equivocals by chance there is no order or reference of one to another, but it is entirely accidental
that one name is applied to diverse things: the application of the name to one of them does not signify
that it has an order to the other. But this is not the situation with names said of God and creatures, since
we note in the community of such names the order of cause and effect, as is clear from what we have
said. It is not, therefore, in the manner of pure equivocation that something is predicated of God and other
things.
urthermore, where there is pure equivocation, there is no likeness in things themselves; there is only the
unity of a name. But, as is clear from what we have said, there is a certain mode of likeness of things to
God. It remains, then, that names are not said of God in a purely equivocal way.
Carl: Metaphysics 122
In c. 34’s treatment of the analogy between creatures and God, St. Thomas offers a division
of the kinds of analogical predication, but one that is different from that found in the De veritate.
The division of analogy is as follows:
(1) “As many things have reference to something one. For example, with reference to one
health, an animal is healthy as the subject of health, medicine is healthy as its cause, food as its
preserver, urine as its sign.”
(2) “As the order or reference of two things is not to something else but to one of them.
Thus, being is said of substance and accident according as an accident has a reference to a
substance, and not according as a substance and accident are referred to a third thing.”
St. Thomas excludes analogical predication in the first way with regard to the names said
of God and creatures. Instead, he explains that analogy is according to the second mode, that of
analogy according to the reference or relation of one to another. What St. Thomas means to
exclude here is the possibility that God and creatures could share, even by analogical community,
in some perfection that is distinct from both of them: as if there were a being or a goodness distinct
from God and creatures in which both God and creatures could share. This is impossible, because
God is being itself and goodness itself. St. Thomas also means to exclude that God could be said to
participate in some abstracted perfection; there is no tertium quid between God and creatures in
which both commonly participate by analogy.
St. Thomas then explains that although being and goodness belong primarily to God in
reality (because He is esse itself and goodness itself) and to creatures secondarily or in a posterior
way, nevertheless we first know creaturely being and creaturely goodness (and all the other
creaturely perfections from which we name God). Therefore these names are primary to creatures
in the order of discovery (in which we come to name God from His effects), but primary to God in
the order of reality. Similarly, medicine is the cause of health, but it is called healthy from its
effect.
A significant worry: extrinsic denomination
That St. Thomas here draws a comparison between the example of health and the
analogical predication of names such as being and goodness of God has occasioned commentators
to worry that this kind of analogical predication does not reflect any intrinsic similarity between
the various realities. That is, medicine’s being healthy involves no intrinsic likeness to the health of
the body that it causes: this example of analogy is a case of what is called extrinsic denomination,
the naming of something from something extrinsic and not necessarily similar to it. Those thinkers
that have historically favored an interpretation of St. Thomas influenced by Cajetan (which
privileges four-term proportionality as the only analogy that preserves a connection between God
and creatures that speaks to something intrinsic rather than something merely extrinsic) have done
so out of a worry about whether the analogy of one to another can preserve an intrinsic connection
between the being and goodness of a creature and the being and goodness of God.
To answer this concern, we should turn to our next theme, the development in St. Thomas’s
thought from an emphasis on exemplar formal causality as the foundation of analogy, to his
emphasis on efficient causality and its consequent likeness.
Carl: Metaphysics 123
16.2. The Causal Relationship at the Heart of Analogy
Commentary on the Sentences
In In Sent. 1.35.1.4 asks the same question as DV 2.11, whether divine scientia is univocal
with creaturely scientia. Having offered arguments against univocity and pure equivocation, St.
Thomas draws a distinction between two kinds of analogical predication, just as he did in the texts
we have already considered.
In this case there is a distinction between:
(1) Analogical predication according to a common form possessed according to the prior
and the posterior (per prius et posterius). This is how St. Thomas explains the predicamental
analogy of the categories elsewhere in the Sentences Commentary; but here he denies that the
analogy between creatures and God is according to the prior and the posterior.
(2) Analogy according to participation based on an imperfect likeness. This is how St.
Thomas characterizes the transcendental analogy between creatures and God.
Why does St. Thomas exclude analogy according to the prior and posterior in this text?
Here he describes this kind of analogy as “sharing in something one which belongs to both;” this
sounds rather like the analogy of many to one as St. Thomas later distinguishes it in the Summa
contra Gentiles. This suggests that, in the Sentences Commentary St. Thomas does not think that
analogy between God and creatures is according to the prior and the posterior, because he is
concerned to exclude that God and creatures would be thought to share in some common third
thing. St. Thomas later addresses this concern by explicitly distinguishing between the analogy of
many to one and the analogy of one to another, as we saw in the Summa contra Gentiles 1.34:
By his preference for what Montagnes has called analogy according to participation based
on an imperfect likeness, in the Commentary on the Sentences St. Thomas establishes the exemplar
formal causality of the divine essence as the foundation for analogical predication of names. It is
because creatures imperfectly imitate the divine exemplar that certain names can be predicated
analogically of both. Montagnes’ thesis is that DV 2.11 serves to address the quite reasonable fear
that such a comparison according to formal causality would imperil the divine transcendence: a
comparison according to formal likeness would seem to be like the determinate, definite relation
But analogy is twofold. One according to sharing in something one which belongs to them per
prius et posterius; and this analogy cannot be between God and creature, just as univocation
cannot. The other analogy is insofar as one is imitated by another so far as it can, not perfectly
following it; and this is the analogy of a creature to God.
Thus, therefore, because we come to a knowledge of God from other things, the reality in the
names said of God and other things (res nominum de Deo et rebus aliis dictorum) is in God per
prius according to His mode of being, but the meaning of the name (ratio nominis) belongs to Him
per posterius. And so He is said to be named from His effects.
Carl: Metaphysics 124
between two quantities in a mathematical proportion. DV 2.11 offers a solution according to which
imperfect formal likeness can be understood without undermining the divine transcendence.
Omne agens agit sibi simile and consequent likeness
In his later writings, however, St. Thomas emphasizes not the exemplar formal causality of
the divine essence in order to ground analogy, but rather the efficient causality by which God
produces creatures from nothing. According to the principle omne agens agit sibi simile, there is a
likeness between creatures and God necessarily consequent to the act of creation; and thus the
relation and likeness established by efficient causality is what allows the analogical predication of
certain names. There is a relation of one to another that grounds the transcendental analogy: this is
the dependence of creatures upon God as their creating cause.
Unlike the view favored in the Sentences commentary, the relation or proportion grounding
analogy is not directly the comparison between the formal characteristics of God and the imperfect
likeness of those characteristics in creatures; but rather the relation or proportion of efficient
causality is what grounds analogy. That is, against the doctrine of the De veritate, there is a
proportion of God to creatures: that which is established by His being the efficient cause of the
creature. We can briefly cite several texts in which St. Thomas contradicts DV 2.11’s denial that
there is a proportion between creatures and God, by citing the relationship established by efficient
causality as a proportion:97
In DT 1.2 ad 3:
“There is a proportion of creature to God, as caused to cause.”
SCG 3.53:
“Nothing prohibits there being a proportion of the creature to God . . . according to the
relation of effect to cause.”
ST 1.12.1 ad 4:
“There can be a proportion of creature to God, insofar as it is related to Him as an effect to
the cause.”
Montagnes’ theory regarding the developments in St. Thomas’s doctrine of analogy can be
summarized in these stages:
(1) The analogy by participation according to imperfect formal likeness can give rise to the
concern that God’s transcendence is nullified, because analogy seems to consist in a direct
proportion between the perfections of a creature and the perfections of God. That is, analogy can
be said to express just the comparison made between creatures and God, which seems to
undermine the divine infinity and transcendence.
(2) Therefore, St. Thomas proposed the theory of the De veritate to preserve the divine
transcendence. By saying that analogy is based upon a likeness of proportions (the infinite is to the
infinite as the finite is to the finite), St. Thomas can preserve the infinite distance between God and
creatures.
(3) But the solution of the De veritate presents the danger of agnosticism, because it turns
out that there is no direct analogy of being between creatures and God: there is instead an analogy
that compares the relation of God’s knowledge to His infinite being to the relation of creaturely
knowledge to finite creaturely being. Therefore, St. Thomas reverted back in part to the doctrine of
97Cited by Montagnes, 76.
Carl: Metaphysics 125
the Sentences commentary, the analogy by reference to one, but by finding a way that allowed him
to characterize the analogy between God and creatures as one according to priority and
posteriority: the key to this solution is the emphasis on efficient rather than formal causality. As
Montagnes puts it: “Unlike formal causality, efficient causality establishes a relation between
beings and God by which the latter is most intimately present to all that is without ceasing to be
transcendent.”98 By efficient causality (understood with the principle that omne agens agit sibi
simile), St. Thomas can hold both to direct proportion or relation between creatures and God and to
the infinite transcendence of God.
As for this claim that efficient causality establishes a relation by which God is most
intimately present to creatures, while infinitely exceeding them, we should consider the following
from ST 1.8.1 on the divine omnipresence:
From the thesis that God is the proximate efficient cause of esse in creatures, St. Thomas
concludes that God must be most intimately present to all of His creatures: this is because esse is
the act of all acts, the perfection of all perfections, and the most formal and actual principle.
98Montagnes 79.
God is in all things; not, indeed, as part of their essence, nor as an accident, but as an agent is
present to that upon which it works. For an agent must be joined to that wherein it acts
immediately and touch it by its power; hence it is proved in Physics VIII that the thing moved and
the mover must be joined together. Now since God is very being by His own essence, created being
must be His proper effect; as to ignite is the proper effect of fire. Now God causes this effect in
things not only when they first begin to be, but as long as they are preserved in being; as light is
caused in the air by the sun as long as the air remains illuminated. Therefore as long as a thing has
being, God must be present to it, according to its mode of being. But being is innermost in each
thing and most fundamentally inherent in all things since it is formal in respect of everything found
in a thing, as was shown above. Hence it must be that God is in all things, and innermostly.
Carl: Metaphysics 126
16.3. Cajetan on Analogy
It is fitting, both in the study of Thomistic metaphysics in general, but also in particular in
the study of St. Thomas at a Dominican studium, to consider at least briefly the account of analogy
given by Tommaso de Vio Cardinal Cajetan, the great commentator on St. Thomas. With regard to
the issue of analogy, Cajetan’s account of analogy (in De nominum analogia) has had a tremendous
impact on Thomists for centuries. The position on analogy that we have sketched so far—
influenced primarily by Montagnes—is in no small part a reaction against the central elements of
Cajetan’s theory of analogy.
The context and purpose of the De nominum analogia
As Joshua Hochschild emphasizes in The Semantics of Analogy (his extremely helpful
book on Cajetan’s De nominum analogia), generally speaking Thomist critics of Cajetan in the 20th
century took it to be the case that the right question to bring to bear on Cajetan’s account is this: Is
Cajetan’s account of analogy faithful to the writings and thought of St. Thomas himself? Is it the
right interpretation? However, Hochschild argues that this is the wrong question, the wrong
criterion for judging Cajetan’s treatise on analogy. Rather, one must read Cajetan’s account as a
relatively independent attempt to offer a semantic, logical account of analogy that is sufficient to
answer two objections to analogy that are rooted in the thought of Scotus. These two objections
can be roughly stated as follows.
Objections against analogy inspired by Scotus:99
1) At the core of any so-called analogical predication, there must be some element of
univocity, or else there will only be equivocation. That is, the claim that analogy is a proper mean
between univocity and equivocation cannot be maintained. (For this reason, on the Scotistic
account, there must be a univocal concept of being and of any other “transcendental” notions.)100
2) Any use of non-univocal terms will cause the fallacy of equivocation when those terms
are employed in reasoning. That is, analogical terms as St. Thomas conceives of them will cause
the fallacy of equivocation; and since metaphysics employs analogical terms almost exclusively,
metaphysics will not be a science.
It is not our purpose here, however, to consider how it is that Cajetan’s account is an
attempt to answer these objections. One can and should look to Hochschild’s work to consider this
issue—and as Hochschild emphasizes, this is the most appropriate way to approach Cajetan’s
treatise insofar as one is interested in evaluating his work.
Cajetan’s theory and the background in St. Thomas
All that being said, the historical question of whether Cajetan’s account is also the best
interpretation of St. Thomas’s understanding of analogy can still be asked—it should only be borne
in mind that any negative answer would not necessarily be a criticism of Cajetan himself. As
Hochschild himself notes, this is the primary question that has been asked by Thomists since the
mid-20th century, in reaction against the general acceptance of Cajetan’s theory by previous
Thomists. It is not the best question for evaluating Cajetan’s thought—but it is a question to be
considered, nevertheless.
My intention here is only to offer a brief sketch of what might called the standard
interpretation of Cajetan’s theory as an interpretation of St. Thomas, even though we must
99 Hochschild, 39 ff.
100 Scotus’s notion of a “transcendental” is different from St. Thomas’s, at least terminologically: for Scotus,
any term that is predicated in common of both God (the infinite) and creature (the finite) is
transcendental.
Carl: Metaphysics 127
acknowledge with Hochschild that this was not Cajetan’s primary purpose in the De nominum
analogia. To do this, we must first cite a key text from St. Thomas’s Commentary on the Sentences
1.19.5.2 ad 1. This article asks whether or not all things are true by virtue of uncreated truth (utrum
omnia sint vera veritate increata). The first objection argues:
The objection contends that it follows immediately from analogical predication that there
is one primary instance from which all the analogates are denominated; and so if true is an
analogous term, then there must be one primary instance of truth whereby all true things are called
true.
In his reply to this objection, St. Thomas draws a threefold distinction among cases or
ways in which something can be said according to analogy:
The three-fold division of analogy in In Sent. 1.19.5.2 ad 1
(a) according to notion but not according to being (secundum intention tantum, et non
secundum esse)
-This occurs when one notion is related to several things per prius et posterius, which
notion nevertheless only has being (esse) in one of these things.
-For example, the notion of health is related to animal, urine, and a diet in diverse ways,
according to priority and posteriority; and yet this predication is not secundum esse,
because the being of health (esse sanitatis) is present only in the animal (its subject).
(b) according to being but not according to notion (secundum esse et non secundum
intentionem)
-This occurs when several things share equally in some common notion, but that notion
does not have being according to the same ratio in all of these things.
-For example, one can consider all bodies as sharing equally in body taken as a genus (as
one does in the Porphyrian tree), even though in being the celestial bodies and sublunary
bodies do not have being according to the same ratio.
-St. Thomas goes on to explain that in this case, whereas the logician treats body
univocally, the metaphysician recognizes that body is said analogically of these different
kinds of body: this is because the metaphysician considers things secundum esse.
(c) according to notion and according to being (secundum intentionem et secundum esse)
-This occurs when things share equally neither in a common notion nor in being.
-For example, being (ens) is said of substance and accident in this way. Also, it is in this
way that truth, goodness, and other names of this kind are said analogically of God and
creatures.
-In this case it is necessary that the common nature (natura communis) named
For . . . true is said analogically of those things in which there is truth, just as health [is said
analogically] of all healthy things. But one in number is the health from which animal is
denominated healthy as [health’s] subject, and medicine healthy as its cause, and urine healthy, as
its sign. Therefore it seems that one is the truth by which all things are called true.
Carl: Metaphysics 128
analogically have some being in each of the things of which it is said, but differing
according to greater and lesser perfection.
St. Thomas concludes the response to the objection by arguing that truth has being in all of
the analogates (and not just in God, understood as the primary analogate), but not being according
to the same perfection. Therefore, there are diverse truths, and not just one truth from which all
other things are denominated true (in a purely extrinsic fashion).
Now, Cajetan’s presentation of analogy mirrors this threefold presentation, and the famous
Cajetanian names for the kinds of analogy are names that replace the formulas found in In Sent.
1.19.5.2 ad 1: Cajetan calls these analogy of attribution (analogia attributionis), analogy of
inequality (analogia inaequalitatis), and analogy of proportionality (analogia proportionalitas).101
Cajetan’s examples of each of these kinds of analogy are the same as the examples found in In
Sent. 1.19.5.2 ad 1, and in each case he references this text of St. Thomas, citing the Thomistic
formula.
Cajetan’s fundamental division of analogy:102
(a) analogy of attribution: this is the kind of analogy according to which healthy is said of
the animal, medicine, and urine. It is parallel to St. Thomas’s analogy secundum intentionem
tantum, et non secundum esse.
-Cajetan emphasizes that in this analogy, the primary analogate is a part of the definition of
the secondary analogates: the health that is in the animal as its subject is part of the
definition of healthy when it is predicated of medicine or urine.
-Cajetan contends that it is analogy of attribution that is divided into analogy of two to a
third (analogia duorum ad tertium) and analogy of one to another (analogia unius ad
alterum) by St. Thomas.103
-Cajetan does not consider this to be analogy except in an abusive sense, because the
common nature is present intrinsically in only one of the analogates. Medicine and urine
are not healthy, intrinsically, but are only denominated as healthy because of their relations
(as cause and sign) to health. He notes that from the logician’s perspective (which
Hochschild argues is Cajetan’s own perspective in De nominum analogia) analogy of
attribution is equivocation.
(b) analogy of inequality: this is the kind of analogy according to which body is said of
both celestial bodies and sublunary bodies. It is therefore parallel to St. Thomas’s analogy
secundum esse et non secundum intentionem.
-From the perspective of the logician, as St. Thomas himself says, this kind of analogy is
really univocity. Therefore, while on the one hand this kind of analogy does not raise, for
Cajetan, the troubling worries about equivocation in reasoning; on the other hand, there’s
no reason to give any extended treatment to this kind of analogy in a treatise on analogy
from a semantic or logical perspective.
(c) analogy of proportionality: this is what Cajetan offers as parallel to St. Thomas’s
analogia secundum intentionem et secundum esse. Interpreting Cajetan’s theory as an interpretation
101 De nominum analogia, c. 1 (4).
102 Cajetan treats analogy of inequality first, because he does not think it is really analogy at all; I have
reordered the treatment to reflect the parallels with In Sent. 1.19.5.2 ad 1, which, again, Cajetan himself
cites.
103 DNA, c. 2 (19).
Carl: Metaphysics 129
of St. Thomas, this identification would fatefully combines the account of analogy from DV 2.11
with the division of analogy in In Sent. 1.19.5.2 ad 1.
-As an initial example, Cajetan offers the following: bodily vision and intellectual vision
are both called vision, because as the intellect is comparable to the eye, insofar as the
intellect is related to its object in a manner similar to how the eye is related to its object.
-It is only this kind of analogy that is analogy properly speaking, for Cajetan. It is a true
mean between equivocation and univocity, and he defends the claim that one can employ
terms analogous in this way in one’s reasoning without committing the fallacy of
equivocation.
-Following the suggestion of In Sent. 1.19.5.2 ad 1, Cajetan treats the analogy of being on
both the “horizontal” and the “transcendental” levels according to the analogy of
proportionality.
Carl: Metaphysics 130
17. Divine Operations: Knowledge, Will, Power
Just as we offered some brief commentary on the meaning of the various divine names
treated from Ia qq. 6 – 11 in the Summa theologiae, so now we will offer some brief commentary
on the names treated by St. Thomas in connection with the divine operation.
St. Thomas introduces this section of the Summa theologiae (Ia qq. 14 – 26) in the
following way, in the prologue to q. 14:
These latter divine names are discussed under the heading of divine operations. Now, in
finite creatures, operations are accidents that are distinct from the substances in which they exist.
In God, there is no substance-accident composition, and therefore each of these names of divine
operations names the divine essence itself, but understood according to a distinct ratio.
14.1. Divine Knowledge
How it is established that there is knowledge in God
Concerning argumentation for knowledge in God in q. 14 a. 1, it should be noted that
curiously St. Thomas does not base any argument upon the claim that God is perfect or possesses
in a more eminent way the perfections of all things. (St. Thomas does offer this sort of argument
for divine intelligence in the Summa contra Gentiles I c. 44). Instead, he simply argues that God’s
having knowledge follows from His absolute immateriality: to be an immaterial substance is to be
an intellectual substance, because an intelligent being is one that can naturally possess the form of
something besides itself. Immateriality is the cause of intelligence. Since God is immaterial in the
highest degree, it follows that He also is the highest in knowledge.
In the subsequent articles of q. 14, St. Thomas explains that God primarily knows and
comprehends Himself, because in God there is no distinction between His intellect and His
essence: therefore the primary object of the divine intellect is just the divine essence itself. God
comprehends Himself because the power of His intelligence is equal to the infinite perfection of
His essence, because He is pure act without any potency or principle of limitation.
The divine ideas
As regards the knowledge of things besides Himself—that is, the things that He creates—
St. Thomas explains that God knows other things by knowing Himself, insofar as He is the cause
After consideration of those things that pertain to the divine substance, remaining to be considered
are those things that pertain to His operation. And since one kind of operation is that which
remains in the one operating, but another is that which proceeds to an exterior effect; first we will
deal with knowledge and will (for to understand is in the one understanding, and to will is in the
one willing); and afterward about the power of God, which is considered as the principle of the
divine operation proceeding into exterior effects. . .
Carl: Metaphysics 131
of other things that are like Him as various imperfect imitations of His essence. In q. 15, St.
Thomas discusses the notion of the divine ideas. The divine ideas are the exemplar forms of the
things that God creates, the “plans,” as it were, according to which God creates particular things:
the divine ideas are thus analogous to the ideas of artisans and builders.
The divine ideas are many, because God can create many different kinds of things. The
divine ideas are just this: God’s understanding of the various ways in which His essence can be
imperfectly imitated by creatures. Every creature is unlike and falls short of God, but some are
unlike God in more ways or to a greater degree than others. For example, a lion is less unlike God
than a rock; and a human being is less unlike God than a lion.
It should also be noted that the divine ideas according to which God creates are not His
ideas of genera or species (although He does have such ideas), but rather His ideas of individuals.
The individual essence of a given corporeal substance includes not just its matter taken universally,
but its particular matter. God understands the individual essence of a corporeal substance in a way
that no human intellect can, by understanding its particular matter as well as its form.
14.2. Divine Will
Divine will is treated in Summa theologiae I q. 19. That God has will is argued for from
the fact that will naturally follows upon intellect, because will is nothing but the intellectual
appetite, where appetite is understood as inclination towards the good. Because God is the supreme
and most perfect good, He primarily wills His own goodness. Everything else that God wills is
ordered to Himself as an end, so as to allow creatures to share in His infinite goodness.
One of St. Thomas’s central concerns (in aa. 3 and 5) is to argue that God’s will is free: it is
not the case that God wills whatever He wills necessarily. God does will His own goodness
necessarily, but all of those things that He wills for the sake of His goodness He wills freely. (In a
similar way, freedom in the human will concerns the election of the means by which an intended
end is pursued.) Indeed, St. Thomas affirms that no cause can be assigned for the divine will,
because just as God understands all things in understanding Himself, so He wills what He wills in
willing His goodness. That is, by the same simple act God wills both Himself and whatever else He
wills. Another way of recognizing the same claim, then, is to remember that God’s intellect and
will are in reality both identical with the divine essence, and the divine essence cannot be related to
itself as a cause.
14.3. Divine Power and Omnipotence
Although there is no passive power in God—that is, a capacity to be acted upon by
something else—there is active power, the capacity to produce an effect distinct from Himself.
Because God is pure act, it belongs to Him to be capable of acting as an efficient cause—indeed, it
should be recalled that the foundation for establishing God’s existence and many of His attributes
was the recognition that there must be a first efficient cause of all things. The notion of active
power is the principle of an external effect. Because God is the principle of external effects, as an
efficient cause, He is said to be active power. Indeed, just as with His other attributes, God is
identical with His power.
St. Thomas also argues for the two very closely related claims that God’s power is infinite
and that He is omnipotent. These are slightly distinct claims: God is said to possess infinite power
because His power is identical with His infinite essence. It is the infinite character of God’s power
that serves to explain why God is capable of the act of creation, whereas no other being is capable
of creating anything ex nihilo. That is, the claim that God’s power is infinite is primarily a claim
Carl: Metaphysics 132
concerning the degree of the divine power: by His power God is capable of doing something that
requires unlimited power.
By contrast, to say that God is omnipotent means that God is capable of doing absolutely
anything that is possible, i.e., anything that does not involve a contradiction. In articulating the
notion of absolute possibility in this way, St. Thomas is dependent upon Aristotle’s Metaphysics,
which he references in q. 25 a. 3. God can do anything that does not involve or imply a
contradiction. To say that God cannot do what involves a contradiction is not to place any limit on
God’s power, because what is contradictory simply cannot be.
Significance of the late treatment of divine power
It is worth taking note of the fact that St. Thomas treats the notion of divine power and
omnipotence virtually last in the order of the divine names. That is, power or omnipotence is not
the first thing to be established concerning God (even though one could establish it much earlier in
the order of the attributes, since the arguments for God’s power depend upon His being an efficient
cause and pure act, things established by Ia q. 3 a. 1). In contrast to later theology of the early 14th
century, St. Thomas does not place a central emphasis on the notions of divine will and power. He
does argue both that God is free and that God is omnipotent, but these are not the first things to be
said concerning the divine essence.
By contrast, theologians such as Ockham afford such a central place to the notion of divine
omnipotence that it becomes as it were one of the absolutely first principles of theology and
philosophy. For example, Ockham argues from the divine omnipotence—which implies that God is
capable of producing immediately by His power any effect that can be produced by any secondary
(i.e., creaturely) cause—to metaphysical conclusions, such as the denial of the reality of any
categories of being besides substance and quality. In St. Thomas, although divine omnipotence is
affirmed, it is not the first or most important thing to be said concerning the divine essence. After
all, it concerns more what God can hypothetically do, rather than what He does in fact will to do.

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Carl: Metaphysics 1
Metaphysics: Fall 2020
Brian Thomas Carl, Ph.D.
Center for Thomistic Studies
Schedule of Topics & Readings
A. What is Metaphysics?
0. Introduction to the Study of Metaphysics: Wippel 3-22, In Met. pr.
1. The knowledge of being: Wippel 23-44, In DT 5.3
2. Separatio and the knowledge of being as being: Wippel 44-62, In DT 5.3
B. Being and beings: Analogy and Participation
3. The one and the many: Wippel 65-73
4. Analogy I: the meaning of analogy and the “horizontal” analogy: Wippel 73-93
5. Participation: Wippel 94-131
C. The Composite Character of Ens Commune
6. Real composition and distinction of essence and esse: Wippel 132-161
7. Substance-accident composition: Wippel cc. 7-8, esp. pp. 197-228, 253-61
8. Matter-form composition in corporeal substances: Wippel c. 9, esp. 312-327, 351-75
9. Comparison and coordination of the modes of composition: potency and act
D. Transcendentals
10. The transcendentals: DV 1.1; In Met. 4.2, 10.3; ST 1.16.1-4; ST 1.5.1-4
E. Natural Theology I: God’s Existence
11. How God is known through natural reason: ST 1.2.1-2
12. Argumentation for God’s existence: the first way: ST 1.2.3, Wippel 444-59
F. Natural Theology II: Knowing and Naming God
13. Simplicity: God as ipsum esse per se subsistens: ST 1.3.1-8
14. Establishing divine perfection: ST 1.4.1-3
15. Divine naming: the threefold way: ST 1.12
16. Analogy II: “transcendental” analogy and divine names: ST 1.13
17. Divine operations: intellect, will, power: ST 1.14, 1.19, 1.25
Carl: Metaphysics 2
ABBREVIATIONS
CT Compendium theologiae
De ente De ente et essentia
De prin. De principiis naturae
De malo Quaestiones disputatae de malo
De pot. Quaestiones disputatae de potentia Dei
De spirit. creat. Quaestio disputata de spiritualibus creaturis
De ver. Quaestiones disputatae de veritate
In De an. Sententia libri De anima
In DN In librum Beati Dionysii De divinis nominibus expositio
In DT / SBDT Super Boetium de Trinitate
In Ethic. Sententia libri Ethicorum
In Meta. In duodecim libros Metaphysicorum Aristotelis expositio
In Per. Expositio libri Peryermenias
In Phys. In octos libros Physicorum Aristotelis expositio
In Post. Expositio libri Posteriorum
In Sent. Scriptum super libros sententiarum magistri Petri Lombardi
LR Lectura romana in primum Sententiarum Petri Lombardi
Quodl. Quodlibeta
Resp. (108) Responsio ad magistrum Ioannem de Vercellis de 108
articulis
SCG Summa contra Gentiles
ST Summa theologiae
Carl: Metaphysics 3
1. The Knowledge of Being
As already indicated, metaphysics is the philosophical science that studies being, or, to be
more precise, being as being. What does this mean? It will be the purpose of the first two sections
of the course to begin to address this question. We will begin with a consideration of the following
question: how is being known by human beings?
1.1. Background: Apprehension and Judgment
In order to understand the Thomistic position concerning the knowledge of being, it is
necessary first to recall the distinction, drawn in logic (as well as in the study of human nature and
in epistemology), between apprehension and judgment as two of the three operations (along with
reasoning) of the human intellect.
Apprehension
By the act of apprehension, the human intellect grasps the quiddity or essence of a
(corporeal) reality: this is to say that the intellect grasps what something is. We can consider a text
from St. Thomas’s early De ente et essentia, c. 1, for a treatment of what he means by the term
quiddity:
Et quia illud per quod res constituitur in proprio
genere vel specie est hoc quod significatur per
diffinitionem indicantem quid est res, inde est
quod nomen essentiae a philosophis in nomen
quidditatis mutatur; et hoc est etiam quod
Philosophus frequenter nominat quod quid erat
esse, id est hoc per quod aliquid habet esse quid.
Dicitur etiam forma, secundum quod per formam
significatur certitudo uniuscuiusque rei, ut dicit
Avicenna in II Metaphisicae suae. Hoc etiam alio
nomine natura dicitur, accipiendo naturam
secundum primum modum illorum quatuor quod
Boetius in libro De duabus naturis assignat:
secundum scilicet quod natura dicitur omne illud
quod intellectu quoquo modo capi potest, non enim
res est intelligibilis nisi per diffinitionem et
essentiam suam; et sic etiam Philosophus dicit in V
Metaphysicae quod omnis substantia est natura.
Tamen nomen naturae hoc modo sumptae videtur
significare essentiam rei secundum quod habet
ordinem ad propriam operationem rei, cum nulla
And since that through which a thing is constituted
in its proper genus or species is what is signified
through the definition indicating what the thing is,
therefore the name of essence was changed by
philosophers to the name “quiddity”; and this is
also what the Philosopher frequently calls “the
what it was to be,” that is, that through which
something has a [certain] kind of being. It is also
called form, inasmuch as through form the reality
of any thing is signified, as Avicenna says in Book
II[I] of his Metaphysics. This is also by another
name called the nature, taking nature according to
the first meaning of the four which Boethius
assigns in the book Of [the Person and] the Two
Natures: according to the way, namely, that
everything which can be received in any way by
the intellect is called nature, for a thing is not
intelligible except through its definition and
essence; and thus the Philosopher also says in
Book V of the Metaphysics that every substance is
a nature. Nevertheless the name of nature taken in
Carl: Metaphysics 4
res propria operatione destituatur; quidditatis vero
nomen sumitur ex hoc quod per diffinitionem
significatur. Sed essentia dicitur secundum quod
per eam et in ea ens habet esse.
this way seems to signify the essence of a thing
insofar as it has an order to the proper operation of
the thing, since no thing lacks its proper operation;
but the name of quiddity is taken from what is
signified through the definition. But it is called
essence insofar as through it and in it a being has
[the act of] being.
-Quiddity comes from quid est, what-it-is
-Essence is the term used to translate Aristotle’s to ti en einai, the what-it-was-to-be (also
sometimes rendered in Latin as quod quid erat esse)
-form and nature are other terms that can signify what is signified by the term quiddity, but
they do so with different connotations
The quiddity or essence that is grasped by the act of apprehension is expressed through a
definition: that is, a definition is the sign of what is grasped in the act of apprehension, just as a
single word is a sign of something understood. Unlike a single word, a definition is complex in the
sense that it is composed of several words: nevertheless, a definition is simple in the sense that it
expresses one apprehended quiddity. So, for example, one expresses what one grasps in the
apprehension of the quiddity of a triangle through the definition, “three sided planar figure.” In
apprehending a quiddity, one knows a thing as it is distinct from other things, and this is why
knowledge of a quiddity is expressed through a definition, which takes the typical form of a genus
and difference.1
The apprehension of a given quiddity can be more or less distinct, as for example one
might know a horse or a dog only as an animal rather than as distinct from other animals. St.
Thomas observes that in such a case, one knows the quiddity “animal” less distinctly too, because
one knows a universal whole more distinctly when one knows its parts, i.e., the species contained
within it (ST 1.85.3):
Manifestum est autem quod cognoscere aliquid in
quo plura continentur, sine hoc quod habeatur
propria notitia uniuscuiusque eorum quae
continentur in illo, est cognoscere aliquid sub
confusione quadam. . . . Cognoscere autem
distincte id quod continetur in toto universali, est
habere cognitionem de re minus communi. Sicut
cognoscere animal indistincte, est cognoscere
animal inquantum est animal, cognoscere autem
But it is manifest that to know something in which
many things are contained, without having a proper
knowledge of each of those things which are
contained in it, is to know something under a
certain confusion. . . . But to know distinctly that
which is contained in a universal whole is to have
knowledge of a less common thing. Just as to know
animal indistinctly is to know animal insofar as it
is animal; but to know animal distinctly is to know
1SCG 3.46: “But through knowing about a thing what it is, the thing is known just as it is distinct from other
things: therefore also a definition, which signifies what a thing is, distinguishes the definitum from all
other things.” [“Per hoc autem quod scitur de re quid est, scitur res prout est ab aliis distincta: unde et
definitio, quae significat quid est res, distinguit definitum ab omnibus aliis.”]
Carl: Metaphysics 5
animal distincte, est cognoscere animal inquantum
est animal rationale vel irrationale, quod est
cognoscere hominem vel leonem. Prius igitur
occurrit intellectui nostro cognoscere animal quam
cognoscere hominem, et eadem ratio est si
comparemus quodcumque magis universale ad
minus universale.
animal insofar as it is rational or irrational animal,
which is to know man or lion: therefore it first
happens to our intellect to know animal before it
knows man: and it will be the same if we compare
whatever is more universal to what is less
universal.
In general, human knowledge proceeds from the more universal to the less universal: one
distinguishes animal before one distinguishes particular species of animal.2 There is thus progress
in one’s apprehension of any given quiddity, as one proceeds from a more universal and confused
grasp of that quiddity to a clearer knowledge of that quiddity as it is distinct from others.
Judgment
By the act of judgment—also called composition and division—the human intellect
combines and separates the indivisible intelligibles known through the act of apprehension. For
example, the judgment that the dog is white involves both the quiddity “dog” (a substance) and the
quiddity “white” (a quality). Judgment as an act thus depends upon the act of apprehension: one
cannot judge that something is such and such without some apprehensive grasp of the parts of the
judgment. In this instance, as in others, what is complex must be reduced to what is simple.
According to Aristotle, truth and falsity arise only in judgment, rather than in the
apprehension of indivisibles. By apprehension, one only knows what something is, and to fail to
know what something is is to be in a state of ignorance rather than falsity. But when one judges
that something is the case, then there can be truth or falsity about one’s intellectual act.3
In addition to the quiddities that are linked or divided in a judgment, there is the verb
copula itself—is or is not—which expresses the very composition or division of the judgment. In
speech, the most common use of the verb to be is in order to express the intellectual act of
judgment. This provides an important clue concerning the answer to our question about how it is
that the intellect knows being: we will now examine an answer to this question.
1.2. The Knowledge of Being (or Existence)
Given the distinction between apprehension and judgment as operations of the human
intellect, the question arises whether the human intellect knows being through the former or the
latter. As indicated above, the apprehension of a thing’s quiddity can be more or less distinct,
according to a greater or lesser degree of universality. A dog can be understood more generally as
an animal, or as a living thing, or as a body, or as a substance. These levels of increasingly greater
universality about the knowledge of one being, a dog, might suggest that the knowledge of being is
itself acquired through apprehension: according to this suggestion, being would be the most
general quiddity or essence, a most general universal under which all the objects known by the
human intellect would fall.
2See Physics 1.1: “Similarly a child begins by calling all men ‘father,’ and all women ‘mother,’ but later on
distinguishes each of them.”
3This will be explored in greater depth in our treatment of truth (during our study of the transcendentals) later
in the semester.
Carl: Metaphysics 6
However, there is a problem with this suggestion that being is simply the most universal
object of the act of apprehension. As we will explain below (among other places, in discussion of
the analogical character of being), it cannot be the case that being is a genus.4 But if being cannot
be a genus, then it cannot be the case that one arrives at one’s knowledge of being just through the
kind of abstraction involved in the act of apprehension. How then does a human being know
being?
To prepare for our consideration of this question, it will be helpful to briefly consider some
of the Latin terminology used by St. Thomas. Several different Latin terms associated with the
verb esse, which might all be translated into English as ‘being,’ have subtly distinct meanings in the
Latin. In this instance, an awareness of the Latin terminology serves to enrich understanding in a
crucial way. Therefore, throughout this course I will make frequent reference to these terms in the
Latin. It should be noted that even in this first section of the notes, the term being has already been
used in ways that are distinguished in Latin.
esse – the infinitive, “to be”; can be translated as being, the act of being, or existence
ens – the present participle of esse; typically used to refer to a concrete being
essentia – almost exclusively translated as essence, although sometimes as being
St. Thomas’s answer to the question raised is that it is through the intellect’s second act that
being, in the sense of a thing’s actual existence, is known. Or, to put it in another way, it is through
the intellect’s second act that there is a grasp of real being: the judgment expressed as “the thing is”
is the expression of the mind’s grasp of the real being of the thing. St. Thomas sets forth this view
in a number of texts. For example, in DT, 5.3, he begins by stating the distinction between
apprehension and judgment, the intellect’s first and second operations:
Sciendum est igitur quod secundum philosophum
in III de anima duplex est operatio intellectus. Una,
quae dicitur intelligentia indivisibilium, qua
cognoscit de unoquoque, quid est. Alia vero, qua
componit et dividit, scilicet enuntiationem
affirmativam vel negativam formando.
Et hae quidem duae operationes duobus, quae sunt
in rebus, respondent. Prima quidem operatio
respicit ipsam naturam rei, secundum quam res
intellecta aliquem gradum in entibus obtinet, sive
sit res completa, ut totum aliquod, sive res
incompleta, ut pars vel accidens. Secunda vero
We must realize, therefore, that as the Philosopher
says (De anima III) the operation of the intellect is
twofold: one, which is called the “understanding of
indivisibles,” by which it knows what a thing is.
But another, by which it composes and divides,
that is, by forming affirmative and negative
statements.
And these two operations correspond to two
[principles] in things. The first operation concerns
the nature of a thing, in virtue of which the thing
understood holds a certain rank among beings,
whether it be a complete thing, like some whole, or
an incomplete thing, like a part or an accident. But
4As will be discussed below, the reason for this is that any genus must be divided by differences taken from
outside the genus. If being were a genus, therefore, it would need to be divided by differences taken from
outside of being: but this is impossible, because whatever would be outside the genus of being would be
non-being, which is nothing.
Carl: Metaphysics 7
operatio respicit ipsum esse rei, quod quidem
resultat ex congregatione principiorum rei in
compositis vel ipsam simplicem naturam rei
concomitatur, ut in substantiis simplicibus.
the second operation concerns the very being of a
thing, which results from the union of the
principles of a thing in composite [substances], or
accompanies the thing’s simple nature, as in simple
substances.
The crucial claim here is that it is the intellect’s second operation that concerns the very
being of a thing: secunda operatio respicit ipsum esse rei. How should we understand this claim?
We need to consult a text in which St. Thomas comments on the meaning of the term esse. In In
Sent. 1.33.1.1 ad 1, St. Thomas explains that the term esse can be understood in three ways:
Sed sciendum, quod esse dicitur tripliciter. Uno
modo dicitur esse ipsa quidditas vel natura rei,
sicut dicitur quod definitio est oratio significans
quid est esse; definitio enim quidditatem rei
significat. Alio modo dicitur esse ipse actus
essentiae; sicut vivere, quod est esse viventibus,
est animae actus; non actus secundus, qui est
operatio, sed actus primus. Tertio modo dicitur
esse quod significat veritatem compositionis in
propositionibus, secundum quod “est” dicitur
copula: et secundum hoc est in intellectu
componente et dividente quantum ad sui
complementum; sed fundatur in esse rei, quod est
actus essentiae, sicut supra de veritate dictum est.
But it must be known that esse is said in three
ways. In one way esse expresses the very quiddity
or nature of a thing, as it is said that a definition is
an expression signifying what a being (esse) is; for
a definition signifies the quiddity of a thing. In
another way esse expresses the very act of an
essence; such as “to live,” which is esse in living
things, is the act of the soul; not second act, which
is operation, but first act. In a third way esse is said
as what signifies the truth of composition in
propositions, according to which “is” is called the
copula; and in this sense [esse] with regard to its
completion is in the intellect composing and
dividing; but this [esse in the mind] is founded
upon the esse of a thing, which is the act of an
essence, as was said above about truth.
Esse can mean:
(1) the quiddity of a thing
(2) the act of an essence
(3) the truth of composition as expressed in a proposition by the copula, “is”
So, in the text from the De Trinitate, when St. Thomas says that the intellect’s second
operation concerns the very esse of a thing, in which of these three senses should ipsum esse rei be
taken? It is evident by that by this St. Thomas does not mean a thing’s quiddity, because he has just
clarified that the quiddity of a thing is known by the intellect’s first operation. But he also cannot
mean by esse the truth of composition, because esse in this sense is in the intellect rather than in
things. Furthermore, as St. Thomas indicates in this text from the Sentences Commentary, esse in
the third sense is founded upon esse in the second sense, the act of an essence.
Carl: Metaphysics 8
Thus, by ipsum esse rei, St. Thomas must mean what he has called the act of an essence.
But what is it for an essence to be actual? This is just for it to be, in the sense of existence. It is for
this reason that many recent Thomistic scholars understand the ipsum esse rei that is grasped by the
mind’s second operation to be the existence of the thing.5
We can further clarify this claim, that judgment concerns the esse of a thing, by noting that
there are two kinds of judgments: (1) judgments of attribution and (2) judgments of existence.6 The
example of judgment given earlier—the dog is white—is an example of the former, in which
something is predicated of (or divided from) a subject through the verb copula. But one can also
form the judgment the dog is, that is, the dog exists. This is a judgment of existence, in which
nothing other than the actual existence of the subject is expressed. That a judgment of existence is
possible should serve as an indication that esse in the sense of existence is grasped through the
second operation of the mind.7
Resolution/Analysis and the Apprehensive Grasp of Being
Complementing this text from the Super Boetium De Trinitate 5.3, in many other places St.
Thomas speaks of the knowledge of being (ens) in terms of apprehension, frequently citing
Avicenna, as in the following example from DV 21.4 ad 4:
Cuius ratio est, quia illud quod primo cadit in
apprehensione intellectus, est ens. . . .
The reason for this is because that which first falls
into the apprehension of the intellect is being. . . .
It should be noted that Thomas cites this same principle early in the Super Boetium De
Trinitate itself (DT 1.3 obj. 3), so that it should not in itself be interpreted as contradicting what has
been said about the role of judgment in knowing being in the sense of esse. Just what does St.
Thomas means by this primacy of being (ens) in the order of apprehension? We can turn to another
text in which Thomas cites this Avicennian axiom (ST 1-2.94.2):
In his autem quae in apprehensione omnium
cadunt, quidam ordo invenitur. Nam illud quod
primo cadit in apprehensione, est ens, cuius
intellectus includitur in omnibus quaecumque quis
apprehendit. Et ideo primum principium
indemonstrabile est quod non est simul affirmare et
negare, quod fundatur supra rationem entis et non
entis, et super hoc principio omnia alia fundantur,
ut dicitur in IV Metaph.
But among those things that fall under the
apprehension of all [men], a certain order is found.
For that which first falls into the apprehension is
being, the understanding of which is included in
everything whatsoever that someone apprehends.
And therefore the first indemonstrable principle is
that there is not simultaneous affirmation and
negation, which is founded upon the meaning of
being and non-being; and upon this principle are
founded all the other [principles], as is said in
Metaphysics IV. (ST 1-2.94.2)
5For example, this is the position of Gilson, Fabro, Owens, and Wippel, and their various followers.
6For St. Thomas’s acknowledgment of this distinction, see In Per. 2.2.
7As we will see later in the course, a judgment of attribution also grasps the esse of the thing, according to its
composite character. St. Thomas claims that truth obtains in the intellect’s second operation because
Carl: Metaphysics 9
Here St. Thomas relates the primacy of the principle of non-contradiction to the primacy of
the apprehension of being (ens). What does this text mean by the primacy of the apprehension of
being? Does this not contradict the claim made in DT 5.3 that it is the intellect’s second operation
that grasps ipsum esse rei? To answer this question, we need to do two things: (1) give an account
of the relationship between the terms ens and esse, and (2) briefly discuss the notion of resolution
or analysis (resolutio).
(1) Regarding ens and esse: St. Thomas typically uses the term ens to refer to a being (in
the sense of a concrete being), and he with some frequency clarifies or explains the notion of ens as
id quod est (that which is) or habens esse (something having existence) or quod habet esse (what
has existence).8 It can be said that ens taken in this sense is the most indistinct and universal way in
which any existing thing can be apprehended. That is, it is always possible to apprehend a given
thing as a being (ens)—but it should be noted that one’s grasp of any existing thing known through
sense experience will always have some quidditative content more specific than “being.” In other
words, it will never the case that one can only say (about a given concrete thing known through
sense experience) that it is a being (ens).
However, this apprehensive grasp of ens depends upon the prior grasp of esse through the
intellect’s second operation: this is why the notion of ens is rightly explained as quod habet esse.
The concept of ens can therefore be called a complex concept, insofar as the apprehension of ens
depends upon the intellect’s grasp of esse through its second operation.
(2) Regarding the notion of resolution: whatever is complex and posterior must, according
to St. Thomas, be resolved into that which is simple and prior. Resolutio is the intellectual process
according to which one moves from the posterior to the prior. It is for this reason that it is often
translated into English as analysis. Insofar as the whole project of Aristotelian science is to proceed
from that which is posterior and better known to us to that which is prior and more knowable in
itself, science itself can be characterized as a project of resolution.
St. Thomas distinguishes resolution into two kinds: (a) resolution secundum rem and (b)
resolution secundum rationem. As Msgr. Wippel explains, according to the former kind of
resolution one seeks the extrinsic causes of a given thing; while according to the latter kind of
resolution one examines the intrinsic causes (particularly the formal cause) of the thing, proceeding
from the less universal to the more universal. It is therefore in the order of resolution secundum
rationem that one arrives at being (ens) as the most universal concept according to which a given
thing may be understood.
When it is said that something is first or prior, one must always ask the following question:
Is this priority in time, or in causality, or in the order of resolution, or in some other way? That is,
just because something is said to be first or to be before something else, this does not mean that it
is first temporally or even causally. In the case of the Avicennian axiom that being is what first falls
into the apprehension of the intellect, the “first” here should not be interpreted in a strictly
temporal way; rather, as Msgr. Wippel argues, St. Thomas seems to be referring to priority in the
order of resolution. Being (ens) is that into which whatever the intellect conceives can be resolved.
8See Wippel 33 n. 35 for a selection of references.
Carl: Metaphysics 10
2. Separatio and the Discovery of Being as Being
What we have established up to this point is that, for St. Thomas, esse in the sense of
existence is grasped through the second operation of the intellect. This grasp of esse through
judgment is attained by virtually all human beings: anyone who can understand the meaning of a
proposition of the form “x exists” grasps esse in the sense of actual existence. We have said before
that metaphysics is the science that studies being as being: is esse in the sense of existence—or,
alternatively, ens as that which is—what we mean by this expression, “being as being?”
2.1. The Distinction of the Subject of a Speculative Science: Division of the Sciences
To answer this question, we need to consider the character of the subject of a speculative
science. Every science studies being, because whatever can be known by the human intellect is
always a being.9 The subject of each of the chief speculative sciences (physics, mathematics, and
metaphysics) is distinguished by the mind as a general object of speculation. “Being” taken
generally is not in any way a distinct object of speculation, because every object of human
speculation is a being. Whether one studies dogs, triangles, or words—distinct objects of
speculation—whatever one studies must be a being. So it cannot be that being, either in the sense
of existence (esse) or in the sense of that which is (ens), is the precise subject of metaphysics.
How are the subjects of the chief speculative sciences distinguished? St. Thomas explains
in Super Boetium De Trinitate 5.1 that “the speculative sciences must be divided according to
differences between objects of speculation, considered precisely as such.”10 Now, whenever the
intellect knows an object of speculation, it does so by virtue of an immaterial likeness of the
known existing in the intellect: fundamentally, the activity of intellectual cognition is immaterial in
character.11 This leads St. Thomas to observe that an object of speculation “considered precisely as
such” is separate from matter and motion; and thus the differences among objects of human
speculation will be established by the differing degrees according to which those objects are
separate from matter and motion.
St. Thomas therefore characterizes the distinction among the objects of the chief
speculative sciences in the following way:
science object’s degree of separation from matter
physics can neither exist without matter nor be understood without matter
mathematics can not exist without matter, but can be understood without matter
metaphysics can exist without matter
The objects studied by philosophical physics (i.e., natural philosophy) can neither exist
without matter nor be understood without matter. For example, it pertains to natural philosophy to
study human nature, and: (1) human beings do not exist except in matter, and (2) one does not
understand what a human being is without knowing that a human being has flesh and bones, i.e.,
particular kinds of matter. As a science, natural philosophy does abstract from particular matter (for
example, this flesh and these bones) but not from matter taken universally. It is for this reason that
9The philosophical thesis positing the connection between being and intelligibility can be traced through
Plato to Parmenides. It is a position generally taken for granted by Aristotle.
10In DT 5.1 [Leon. 50.138]: “. . . et ideo oportet scientias speculativas dividi per differentias speculabilium in
quantum speculabilia sunt.”
11This will be a claim familiar to students who have taken courses in the Thomistic philosophy of human
nature or in Thomistic epistemology.
Carl: Metaphysics 11
St. Thomas characterizes the degree of abstraction peculiar to natural philosophy as the abstraction
of the universal from the particular rather than as the abstraction of form from matter.
By contrast, mathematics studies objects that cannot exist without matter, even though they
can be understood without matter. For example, extension (continuous quantity) or a triangle
(which is a shape, a quality) can only actually exist in a material substrate. Nevertheless, one’s
study of such mathematical objects need not make any reference to matter: in other words,
mathematics as a study makes no reference to material causes. Mathematical objects are abstracted
in this way just because they do not exist only in a particular kind of matter: for example, a triangle
can be made of bronze or of wood, without any difference in its properties qua triangle. Because of
the more abstract character of mathematical objects, St. Thomas characterizes this degree of
abstraction as the abstraction of form from matter.
The objects studied in metaphysics are separate from matter to a greater degree, in that
they are capable of existing without matter. St. Thomas lists among the objects studied by
metaphysics such examples as substance, quality, act, potency, one and many. The objects studied
by metaphysics are immaterial in this precise sense: they need not exist in matter. For this reason
the objects studied by metaphysics can be said to be negatively or neutrally immaterial, as opposed
to what is positively immaterial (as for example angels or God).12
2.2. Separatio and the Discovery of the Subject of Metaphysics
From what has been said, it is clear that esse taken in the sense of actual existence is not
the subject of metaphysics. A person can grasp the notion of existence without grasping being as
something that does not depend upon motion and matter: but it is being understood in just this
latter way that is the subject of metaphysics. How then is the subject of metaphysics known? The
objects of physics are known by abstraction of the universal from the particular; the objects of
mathematics are known by the abstraction of form from matter. What of the subject of
metaphysics?
According to St. Thomas, being as being is not known through just any judgment, but
rather through a special kind of judgment which he terms separation (separatio). In this section of
our course, we will examine his comments concerning this judgment. This will effectively be an
extended commentary on the closing section of the In DT 5.3. (I am providing Fr. Armand Maurer’s
translation of this key text.)
Sic ergo intellectus distinguit unum ab altero aliter
et aliter secundum diversas operationes; quia
secundum operationem, qua componit et dividit,
distinguit unum ab alio per hoc quod intelligit
unum alii non inesse. In operatione vero qua
intelligit, quid est unumquodque, distinguit unum
ab alio, dum intelligit, quid est hoc, nihil
intelligendo de alio, neque quod sit cum eo, neque
quod sit ab eo separatum. Unde ista distinctio non
Accordingly, through its various operations the
intellect distinguishes one thing from another in
different ways. Through the operation by which it
composes and divides, it distinguishes one thing
from another by understanding that the one does
not exist in the other. Through the operation,
however, by which it understands what a thing is, it
distinguishes one thing from another by knowing
what one is without knowing anything of the other,
12This is the language used by Msgr. Wippel. See Wippel 44.
Carl: Metaphysics 12
proprie habet nomen separationis, sed prima
tantum. Haec autem distinctio recte dicitur
abstractio, sed tunc tantum quando ea, quorum
unum sine altero intelligitur, sunt simul secundum
rem.
either that it is united to it or separated from it. So
this distinction is not properly called separation,
but only the first. It is correctly called abstraction,
but only when the objects, one of which is known
without the other, are one in reality.
Separation is the act by which one understands “that one does not exist in the other.” It
therefore differs from abstraction, properly speaking, because abstraction always involves the
mental separation of things that are one in reality (such as the universal and the particular, or form
and matter). While abstraction in this strict sense13 is according to the intellect’s first operation
(because to name a universal abstracted from the particular or a form abstracted from matter is to
state what something is), separation in the strict sense delineated here is according to the intellect’s
second operation, which is judgment. St. Thomas elaborates on this claim about separation as
opposed to abstraction later in q. 5 a. 3:
In his autem quae secundum esse possunt esse
divisa, magis habet locum separatio quam
abstractio. Similiter autem cum dicimus formam
abstrahi a materia, non intelligitur de forma
substantiali, quia forma substantialis et materia sibi
correspondens dependent ad invicem, ut unum sine
alio non possit intelligi, eo quod proprius actus in
propria materia fit. Sed intelligitur de forma
accidentali, quae est quantitas et figura, a qua
quidem materia sensibilis per intellectum abstrahi
non potest, cum qualitates sensibiles non possint
intelligi non praeintellecta quantitate, sicut patet in
superficie et colore, nec etiam potest intelligi esse
subiectum motus, quod non intelligitur quantum.
Substantia autem, quae est materia intelligibilis
quantitatis, potest esse sine quantitate; unde
considerare substantiam sine quantitate magis
pertinet ad genus separationis quam abstractionis.
But in the case of things that can exist separately,
separation rather than abstraction obtains.
Similarly, when we say form is abstracted from
matter, we do not mean substantial form, because
substantial form and the matter correlative to it are
interdependent, so that one is not intelligible
without the other, because the appropriate act is in
its appropriate matter. Rather, we mean the
accidental forms of quantity and figure, from
which indeed sensible matter cannot be abstracted
by the intellect, because sensible qualities cannot
be understood unless quantity is presupposed, as is
clear in the case of surface and color. And neither
can we understand something to be the subject of
motion unless we understand it to possess quantity.
Substance, however, which is the intelligible
matter of quantity, can exist without quantity.
Consequently, the consideration of substance
without quantity belongs to the order of separation
rather than to that of abstraction.
13I add the qualification “in the strict sense” here because at times St. Thomas uses the term abstraction more
generally so as to include both abstraction in the strict sense (which is according to the intellect’s first
operation) and separation (which is according to the intellect’s second operation).
Carl: Metaphysics 13
St. Thomas begins by discussing the abstraction of mathematical objects. He notes that
when it is said that one abstracts form from matter, this does not mean that one abstracts the
substantial form from matter—such an abstraction is not possible, because a corporeal substance is
not intelligible apart from its appropriate matter. Rather, what one abstracts in mathematics are
quantities and figures (a kind of quality), which do not depend upon a particular kind of matter for
their existence. (That is, they can exist in bronze, in wood, etc., which are different kinds of
substance.)
These quantitative and qualitative forms are therefore abstracted from what St. Thomas
calls sensible matter, by which he means material things insofar as they are known through their
sensible qualities. It is possible to abstract quantity and figure from sensible matter because the
latter presupposes the former for its very intelligibility: for example, one cannot understand color
(a sensible quality) without knowing that it is an accident of a surface. However, one does not
abstract quantity or figure from matter absolutely, because quantity and figure are always accidents
of a substance. By the phrase intelligible matter, St. Thomas means the matter that “exists in
sensible things, but not insofar as they are sensible.”14 Intelligible matter is grasped only by the
intellect, which grasps substance as what underlies all accidents. When one abstracts mathematical
objects (such as a triangle), one does not abstract from matter absolutely, but only from sensible
matter.
Thus, although quantity cannot exist without an underlying substance15, substance can
exist without quantity. However, one does not recognize this truth by virtue of any abstraction by
the intellect. Rather, it is by virtue of what St. Thomas above called separation—an instance of the
intellect’s second operation—that one judges that substance is not of itself quantified. To consider
substance in this way, as without quantity, “belongs to the order of separation rather than to that of
abstraction.”
Sic ergo in operatione intellectus triplex distinctio
invenitur. Una secundum operationem intellectus
componentis et dividentis, quae separatio dicitur
proprie; et haec competit scientiae divinae sive
metaphysicae. Alia secundum operationem, qua
formantur quiditates rerum, quae est abstractio
formae a materia sensibili; et haec competit
mathematicae. Tertia secundum eandem
operationem quae est abstractio universalis a
particulari; et haec competit etiam physicae et est
communis omnibus scientiis, quia in scientia
praetermittitur quod per accidens est et accipitur
quod per se est. Et quia quidam non intellexerunt
differentiam duarum ultimarum a prima, inciderunt
We conclude that there are three kinds of
distinction in the operation of the intellect. There is
one through the operation of the intellect joining
and dividing which is properly called separation;
and this belongs to divine science or metaphysics.
There is another through the operation by which
the quiddities of things are conceived which is the
abstraction of form from sensible matter; and this
belongs to mathematics. And there is a third
through the same operation which is the
abstraction of a universal from a particular; and
this belongs to physics and to all the sciences in
general, because science disregards accidental
features and treats of necessary matters. And
14In Metaphysicorum Bk. 7 lec. 10, no. 1496.
15Except by the power of God, as in the Eucharistic species.
Carl: Metaphysics 14
in errorem, ut ponerent mathematica et universalia
a sensibilibus separata, ut Pythagorici et Platonici.
because certain men (for example, the
Pythagoreans and the Platonists) did not
understand the difference between the last two
kinds of distinction and the first, they fell into
error, asserting that the objects of mathematics and
universals exist separate from sensible things.
Here St. Thomas draws his conclusion, associating the two kinds of abstraction with
mathematics and physics and separation with metaphysics, which is also called the divine science.
The objects studied by metaphysics are not abstracted in the strict sense, but are distinguished
through the judgment of separation, in which one negatively judges that being (substance, act,
potency etc.) need not be quantified or material.
The prerequisites for separation
By a careful reading of In DT 5.3, we have established that the objects studied by
metaphysics are grasped by the mind not through abstraction but through a special form of
judgment called separation. In this famous text, however, St. Thomas leaves untreated the question
of how one comes to make the judgment of separation. Among Thomists in the 20th century, the
question of the prerequisites necessary for making the judgment of separation was a source of
significant disagreement. We will sketch here two rival positions.
(1) The River Forest Thomists hold that in order to make the judgment of separation and
begin metaphysics, one must first demonstrate by philosophical argument that positively
immaterial being exists. This can be accomplished by establishing the existence of an immaterial
first cause of motion (as Aristotle establishes in the Physics) or perhaps by proof of the
immateriality of the human soul (as Aristotle takes up in the De Anima). In general, therefore, the
River Forest position is that the study of natural philosophy is not only pedagogically preparatory
for metaphysics, but that it is in fact strictly necessary: on this view, one cannot reasonably study
metaphysics until one knows that positively immaterial being exists, by virtue of previous
philosophical study.
(2) The view favored by authors such as Gilson, Klubertanz, Owens, and Wippel is instead
that one can be in a position to make the judgment of separation without having demonstrated the
existence of the positively immaterial. For example, Msgr. Wippel contends that one already makes
the judgment of separation when one recognizes that a given physical being can be examined
insofar as it is living, or insofar as it is mobile, or insofar as it is material, or simply insofar as it is
a being. That is, what the judgment of separation entails is just that a given being—something that
exists—can be examined just insofar as it is a being, rather than insofar as it is a particular kind of
being. On Msgr. Wippel’s view, St. Thomas’s point in In DT 5.3 is just that the kind of distinction
involved in taking up this perspective—seeing a being qua being—belongs to the order of
separation rather than to the order of abstraction.
It is not my intention to attempt at this point to settle this dispute between River Forest
Thomism and the position generally favored among those, for other reasons, often called
“existential” Thomists, although on this question my opinion tends to favor the latter view. I agree
with Msgr. Wippel that a demonstration in natural philosophy can provide the basis upon which
Carl: Metaphysics 15
one makes the judgment of separation.16 The question is whether or not such a demonstration is the
only way to ground the judgment of separation. However one settles this question about the
prerequisites necessary for the act of separation, it can be held that what this judgment establishes
is that being can be examined simply insofar as it is being. This is what St. Thomas says is the
subject matter of metaphysics.
This being said, in my view, it is possible to begin the project of metaphysics without
having demonstrated the existence of positively immaterial being. That is, one can do just what
Msgr. Wippel claims, which is to consider a being simply insofar as it is a being, even if one has
never demonstrated the existence of the positively immaterial. If one insists that what St. Thomas
calls the judgment of separation can only be justified by a demonstration of the existence of the
positively immaterial, then in my view one could also reasonably conclude that the judgment of
separation is not what establishes the subject of metaphysics; rather, it is a judgment that belongs
to the order of metaphysics.
2.3. Being as Being as the Subject of Metaphysics
The meaning of being as being
As stated above, the subject of metaphysics is being as being or being in general (ens
commune). In his Metaphysics, Aristotle distinguishes the various ways in which being can be
understood in order to clarify the notion of being as being. In Metaphysics 5.7, Aristotle first
distinguishes between accidental being and essential being; he then subdivides essential being into
being in the categories, being as true, and being as actual and potential. I will present these
distinctions as St. Thomas characterizes them in his Commentary on the Metaphysics.
(1) By accidental being (ens per accidens), Aristotle does not mean the being of an
accident, for example the quality white or the relation paternity. Rather, accidental being is that to
which one refers when one predicates something accidentally. For example, that a man is white is
accidental, because it does not belong to the essence of man to be white. The “being” that is
accidental here is what is signified by the underlined is. Aristotle holds that the causes of accidental
being are themselves accidental, such that there cannot be science about this kind of being, since
science is knowledge about the necessary through essential causes.
Essential being (ens per se) is then divided as follows:
(2) Being in the ten categories (or predicaments): St. Thomas calls this being outside the
mind (ens extra animam) and complete being (ens perfectum). Substances and the nine kinds of
accidents are all instances of ens per se, and indeed this is the most important division of essential
being. We will say more about being in the categories in a moment.
(3) Being as true: this is the being of a proposition as composed by the mind. For example,
if I form the judgment that “the apple is red,” this proposition insofar as it is a product of the mind
has being in the mind. St. Thomas explains that it is also the only way in which such things as
privations and negations have being. For example, one can judge that “the dog is blind,” but
blindness is not a real accident of the dog; blindness is rather just the privation of the exercise of
the power of sight in the dog, which is a being that should normally be able to exercise this power.
For this reason being as true is also often referred to as being in the mind.
Being in the categories is then divided as follows:
(4) Being as actual and potential: being in the categories can itself be subdivided in this
16See Wippel 61-62.
Carl: Metaphysics 16
way, into the actual and the potential. For example, a seed is potentially a tree (a substance), and
pale skin is potentially tan (a quality). It is important to note that potential being is an instance of
ens per se extra animam, essential being outside the mind. That is, potential being is not just an
instance of being in the mind, the way that a privation is a being in the mind.17
Of the above divisions of being, Aristotle excludes both accidental being and being as true
from consideration as the subject-matter of metaphysics: these are not being as being or ens
commune as it is studied by metaphysics. This leaves being in the categories, which is further
subdivided into actual and potential being, as the subject-matter of metaphysics. By ens commune
therefore we mean being in the categories, both actual and potential.
God and the subject of metaphysics
In addition to the assertion that metaphysics studies being as being, Aristotle also considers
the possibility that metaphysics studies the highest or best instances of being—these are, for
Aristotle, the separate substances. Aristotle’s attempt at a solution to this question is still a matter of
considerable controversy in scholarly discussions today; what concerns us here is how St. Thomas
answers this question. How is the subject of metaphysics related to the highest being, that is, God?
We can profitably consider St. Thomas’s position on this question in relation to the answers given
previously by the Muslim philosophers Avicenna and Averroes.
Avicenna contends that God (the highest separate substance) is not the subject of
metaphysics, but rather being as being is this science’s subject.18 For Avicenna, metaphysics proves
the existence of God, identifying Him as the first and necessary cause of contingent being. By
contrast, Averroes holds that God’s existence is not established by metaphysics, but rather by
physics (or natural philosophy). According to this latter view, God is the subject of metaphysics as
the first and primary instance of substance: it is because metaphysics studies being as being (which
Averroes takes as primarily meaning substance) that it must study the highest substance in
particular, i.e., God.19
Understanding the positions of Avicenna and Averroes in this way, St. Thomas clearly sides
with the former: St. Thomas contends that the subject-matter of metaphysics is being as being (ens
inquantum est ens) or what he will call being in general (ens commune). Metaphysics primarily
concerns itself with the study of everything that is common to every being, as opposed to the study
of the features that belong only to this or that kind of being. Although God is not the subject of
metaphysics for St. Thomas, nevertheless God is considered by metaphysics—not as its subject,
but as the first cause of being. In other words, metaphysics has as its subject what was termed
above the negative or neutrally immaterial—what is common to all beings—but ultimately
identifies as the cause of its subject what is positively immaterial (God and the separate
substances).
Finally, as we shall explain again and in greater detail later, it is crucially important to note
that God is not a part of the subject of metaphysics: He does not fall under what we will call ens
commune.
17This is a key to Aristotle’s response to the dilemma of Parmenides, who asserted a distinction between
being and non-being that would not allow for the possibility of change. Accepting potential being as real
being serves to defuse this aspect of the Parmenidean dilemma.
18See Wippel 13.
19See Wippel 13-14.
Carl: Metaphysics 17
4. Analogy I: the “Horizontal” Analogy of the Categories
It has become common among contemporary Thomists, following the presentation of
Cornelio Fabro, to distinguish two different levels according to which one can discuss analogy, and
in particular the analogical character of being. We will begin with the notion of analogy that
pertains to ens commune considered in itself; this can be distinguished from the analogy that
obtains between creatures and God.20
4.1. The Notion of Analogy
Univocity and equivocity
To understand the notion of analogy, we must first distinguish between univocity and
equivocity, which are the two basic different ways in which a given term or concept can be related
to two distinct realities. Aristotle draws the distinction between univocal and equivocal terms at the
beginning of his Categories.
A term is used univocally when it is used to name two things, with the same meaning or
definition in each case. For example, when I say that I am a man and that Fr. James is a man, the
term man is used univocally: in each instance that the term is used, it means precisely the same
thing.
By contrast, a term is used equivocally when it is used to name two things, with a different
meaning or definition in each case. For example, bank can refer both to a place where money is
deposited for safe-keeping and the boundary of a river.
Now, according to Aristotle, it cannot be the case that being is a univocal term when it is
taken to refer to substances and to accidents.
Pros hen equivocation
Aristotle distinguishes a third way in which a term can be used, which he calls pros hen
(towards one) equivocation. Strictly speaking, pros hen equivocation is a species of equivocation,
because the same term is used to name two things according to different meanings or definitions.
However, unlike the purely equivocal use of bank or pen to name totally unrelated things, some
terms are used equivocally to name things that are different but closely related to each other.
Aristotle’s most famous example of this kind of equivocation is the term healthy. Consider
the following examples:
(1) The man is healthy.
(2) Exercise is healthy.
(3) Salad is healthy.
(4) The urine is healthy.
The term healthy is used to describe these four things. The use of the term is not univocal. For a
man to be healthy means that his body is generally in good condition, with order and good
operation of his organs. But exercise, salad, and urine do not even have bodily organs: for each of
these things to be healthy cannot be the same thing as for a man to be healthy. Rather, exercise and
salad are called healthy insofar as they are causes of health in a man; and urine is called healthy
insofar as it is a sign of health in a man. This is pros hen equivocation because the meaning of each
of the secondary analogates includes, in its definition, the primary analogate: for example, salad is
20It should be noted that most of the controversy concerning the interpretation of St. Thomas’s thought about
analogy concerns this latter analogy between creatures and God.
Carl: Metaphysics 18
healthy in that it causes the health of a man.
Analogy
Although it is not possible for us to consider at this time the historical background for St.
Thomas’ notion of analogia, we can note that the Thomistic doctrine of analogy has as its most
important precursor the Aristotelian doctrine of pros hen equivocation, but as this was treated and
developed by later Greek and Arabic commentators on Aristotle. Aristotle himself does discuss the
notion of analogia, but for him this term means what it typically means in arithmetic or geometry.
How it is, historically, that pros hen equivocation and analogia came to be intertwined notions is
beyond our present concern. It should only be noted that this historical background helps to explain
some of the developments in St. Thomas’s personal doctrine concerning analogy. However, we will
concern ourselves here only with his mature doctrine.
Just as pros hen equivocation is compared to univocation and equivocation by Aristotle, so
St. Thomas compares analogical predication to both univocal and equivocal predication. In his
early De principiis naturae, c. 6, St. Thomas characterizes these three modes of predication as
follows:
Ad huius intelligentiam sciendum est quod
tripliciter aliquid predicatur de pluribus: univoce,
equivoce et analogice. Univoce predicatur quod
predicatur secundum idem nomen et secundum
rationem eandem, id est diffinitionem, sicut animal
predicatur de homine et de asino: utrumque enim
dicitur animal, et utrumque est substantia animata
sensibilis, quod est diffinitio animalis. Equivoce
predicatur quod predicatur de aliquibus secundum
idem nomen et secundum diversam rationem, sicut
canis dicitur de latrabili et de celesti, que
conveniunt solum in nomine et non in diffinitione
sive significatione; id enim quod significatur per
nomen est diffinitio, sicut dicitur in IV
Metaphysice. Analogice dicitur predicari quod
predicatur de pluribus quorum rationes diverse
sunt, sed attribuuntur uni alicui eidem, sicut sanum
dicitur de corpore animalis et de urina et de
potione, sed non ex toto idem significat in
omnibus: dicitur enim de urina ut de signo
sanitatis, de corpore ut de subiecto, de potione ut
de causa. Sed tamen omnes iste rationes
attribuuntur uni fini, scilicet sanitati.
To understand this it must be known that
something is predicated of several things in three
ways: univocally, equivocally, and analogically.
That is predicated univocally which is predicated
according to the same name and according to the
same intelligible content, which is a definition. In
this way animal is predicated of man and of
donkey: for each is called animal, and each is an
animate sensible substance, which is the definition
of animal. That is predicated equivocally which is
predicated of several things according to the same
name and according to diverse intelligible content.
In this way dog is said of what barks and of a
heaven[ly body], which agree only in name and not
in definition or signification; for that which is
signified through a name is the definition, as is said
in Metaphysics IV. That is said to be predicated
analogically which is predicated of several things
whose intelligible contents are diverse, but are
related to one and the same thing. In this way
healthy is said of the body of an animal and of
urine and of medicine, but it does not signify
entirely the same thing in all of them: for it is said
Carl: Metaphysics 19
of urine as of the sign of health, of the body as of
[its] subject, [and] of medicine as of [its] cause.
Nevertheless all these intelligible contents are
related to one end, namely health.
Whenever something is predicated analogically, it is predicated primarily (per prius) of
one thing and secondarily (per posterius) of other things. The key to understanding St. Thomas’s
notion of analogy is that the secondary analogates are related to the primary analogate according to
some mode of causality: it is causality that provides the connection among the analogates.21 This
causality can be final causality (as it is in the example of health, where the secondary analogates
are ordered to health as an end); it can be efficient causality (as we shall see later in our treatment
of the analogy between God and created being); and it can be material or subject causality.
In commenting on Metaphysics 4.1, St. Thomas offers an important point of development:
Sed sciendum quod aliquid praedicatur de diversis
multipliciter: quandoque quidem secundum
rationem omnino eamdem, et tunc dicitur de eis
univoce praedicari, sicut animal de equo et bove.
Quandoque vero secundum rationes omnino
diversas; et tunc dicitur de eis aequivoce
praedicari, sicut canis de sidere et animali.
Quandoque vero secundum rationes quae partim
sunt diversae et partim non diversae: diversae
quidem secundum quod diversas habitudines
important, unae autem secundum quod ad unum
aliquid et idem istae diversae habitudines
referuntur; et illud dicitur “analogice praedicari,”
idest proportionaliter, prout unumquodque
secundum suam habitudinem ad illud unum
refertur.
Item sciendum quod illud unum ad quod diversae
habitudines referuntur in analogicis, est unum
numero, et non solum unum ratione, sicut est unum
illud quod per nomen univocum designatur.
But it must be known that something is predicated
of diverse [things] in several ways: sometimes
according to entirely the same intelligible content,
and then it is said to be predicated of them
univocally, as animal [is predicated] of horse and
ox. But sometimes according to intelligible
contents in every way diverse: and then it is said to
be predicated of them equivocally, as dog of a star
and of an animal. But sometimes according to
intelligible contents which are partly diverse and
partly not diverse: diverse insofar as they imply
diverse relations, but one insofar as these diverse
relations are referred to something one and the
same; and that is said “to be predicated
analogically,” that is, proportionally, as each of
them according to its own relation is referred to
that one [thing].
Furthermore it must be known that that one, to
which the diverse relations are referred among the
analogates, is one in number, and not only one in
intelligible content, as is the one which is
designated by a univocal name.
21See Wippel 77; Montagnes 26.
Carl: Metaphysics 20
In this text, St. Thomas emphasizes that the primary referent of analogical predication is
always something that is one not merely in ratio (that is, notion or intelligible content) but is also
numerically one: that is, the primary referent of analogical predication is one thing. For example,
in the case of healthy, it is the health (understand as a singular thing, a quality) of the animal that is
the primary referent in relation to which all of the secondary analogates are called healthy.
4.2. The analogy of being on the predicamental level
Although application of the notion of analogy is not restricted to being, nevertheless the
analogy of being is its most famous and most important application in the thought of St. Thomas.
The analogy of being can be formulated on two distinct levels: (1) on the “horizontal” or
predicamental level, according to which being is said analogically of accidents and of substances;
and (2) on the “vertical” or transcendental level, according to which being is said analogically of
God and creatures.22 We will treat the second level of the analogy of being later in our course; for
now, we are concerned with the analogy of being on the predicamental level.
In brief, the theory of Aristotle is that being is a pros hen equivocal term in which the
secondary analogates are the beings in the categories of accidents and the primary analogate is
being in the category of substance.23 St. Thomas holds the same view, but he articulates this claim
in terms of analogy. We will now consider, at length, St. Thomas’s commentary on Metaphysics
4.1.
Dicit ergo primo, quod ens sive quod est, dicitur
multipliciter. . . .
Et ideo dicit quod ens etsi dicatur multipliciter, non
tamen dicitur aequivoce, sed per respectum ad
unum; non quidem ad unum quod sit solum ratione
unum, sed quod est unum sicut una quaedam
natura. . . .
Sed tamen omne ens dicitur per respectum ad
unum primum. Sed hoc primum non est finis vel
efficiens sicut in praemissis exemplis, sed
subiectum. Alia enim dicuntur entia vel esse, quia
per se habent esse sicut substantiae, quae
principaliter et prius entia dicuntur. . . .
Sciendum tamen quod praedicti modi essendi ad
Therefore he says first that being (ens) or what is is
said in many ways. . . .
And therefore he says that being (ens) even if it is
said in many ways, is nevertheless not said
equivocally, but with respect to one; indeed not
[with respect] to a one that is one only in
intelligible content, but which is one as a certain
single nature. . . .
Nevertheless every being (ens) is called [being]
with respect to one first [thing]. But this first
[thing] is not an end or an efficient [cause] as in the
previous examples, but is a subject. For some
things are called beings (entia) or esse, because
they have esse in themelves, such as substances,
which are principally and primarily called beings
(entia).
Nevertheless it must be known that the
22See Wippel 73-74 for this language.
23See Metaphysics 4.1.
Carl: Metaphysics 21
quatuor possunt reduci. Nam unum eorum quod est
debilissimum, est tantum in ratione, scilicet
negatio et privatio, quam dicimus in ratione esse,
quia ratio de eis negociatur quasi de quibusdam
entibus, dum de eis affirmat vel negat aliquid.
Secundum quid autem different negatio et privatio,
infra dicetur.
Aliud autem huic proximum in debilitate est,
secundum quod generatio et corruptio et motus
entia dicuntur. Habent enim aliquid admixtum de
privatione et negatione. Nam motus est actus
imperfectus, ut dicitur tertio Physicorum.
Tertium autem dicitur quod nihil habet de non ente
admixtum, habet tamen esse debile, quia non per
se, sed in alio, sicut sunt qualitates, quantitates et
substantiae proprietates.
Quartum autem genus est quod est perfectissimum,
quod scilicet habet esse in natura absque
admixtione privationis, et habet esse firmum et
solidum, quasi per se existens, sicut sunt
substantiae. Et ad hoc sicut ad primum et
principale omnia alia referuntur. Nam qualitates et
quantitates dicuntur esse, inquantum insunt
substantiae; motus et generationes, inquantum
tendunt ad substantiam vel ad aliquid
praedictorum; privationes autem et negationes,
inquantum removent aliquid trium praedictorum.
aforementioned modes of being can be reduced to
four. For one of these which is the weakest [mode
of being], is [being] only according to reason,
namely negation and privation, which we say exist
according to reason, because [our] reason is
concerned with them as if with certain beings when
it affirms or denies something of them. But in what
way negation and privation differ will be discussed
below.
But another [mode of being] is close to [the first
mode of being] in weakness, insofar as generation
and corruption and motion are called beings
(entia). For they have something admixed with
privation and negation. For motion is the act of the
imperfect, as is said in Physics III.
But the third [mode of being] is called that which
has nothing of non-being admixed, but has weak
being, because [they have esse] not in themselves,
but in another, such as qualities, quantities, and the
properties of substance.
But the fourth kind is that which is most perfect,
which namely has esse in [its] nature without
admixture of privation, and has stable and
complete esse, existing as it were in itself, as are
substances. And to this as to the first and principal
all the others are referred. For qualities and
quantities are said to exist insofar as exist in
substances; motion and generation, insofar as they
tend to substance or to something of the [other]
mentioned [modes of being]; but privations and
negations insofar as they remove something from
the [other] three mentioned [modes of being].
Carl: Metaphysics 22
St. Thomas distinguishes here four modes of being:
(1) The being of privations and negations. -being only according to reason
(2) The being of generation, corruption, and motion. -admixed with non-being
(3) The being of accidents. -being in another
(4) The being of substance. -stable and complete being per se
It is the fourth mode of being distinguished here to which the other three modes are
ultimately referred. Beings of the first mode (privations and negations) are beings of reason, in that
a privation or negation serves to remove or deny being in one of the other three modes (rest is the
negation or privation of motion; blind is the privation of sight; non-substance is the negation of
substance). Beings of the second mode (generation, corruption, and motion) are beings insofar as
they terminate in being in the third or fourth modes—according to Aristotle and St. Thomas,
generation, corruption, and motion occur in the categories of substance, quantity, quality, and
place. Beings of the third mode are related to being of the fourth mode insofar as they exist in
substances as in their subject.
As noted above, for St. Thomas the analogical predication of a term depends upon some
causal relationship that exists among the analogates. In the case of the analogical predication of
being on the predicamental level, the causal relationship between substance and accidents is that
substance is the subject or quasi-material cause of accidents: accidents exist in substances and are
therefore dependent beings. That is, an accident is a being (a habens esse) because it inheres in a
substance, which is being in the primary sense. For this reason, being (ens) is predicated primarily
(per prius) of substance and secondarily (per posterius) of accidents, and the predication of being
as regards accidents is by relation to the category of substance.
Being is not a genus24
Because being is not a univocal term, it is not the case that being is a genus. Every generic
and specific universal term is predicated univocally of the many individuals that fall under these
universals. If being is not a univocal term, then it cannot be a generic or specific universal. Thus,
being is not a genus.25
This conclusion can also be confirmed, as Aristotle argues, by noting that every genus is
divided by differences that are taken from outside the genus.26 Therefore, if being were a genus, it
would have to be divided by non-being. But a difference is always some positive characteristic,
and therefore non-being cannot divide being as if it were a univocal genus.
Therefore, instead of saying that the ten categories are the ten species of being taken as a
genus, St. Thomas prefers to say that the ten categories are ten modes of being. St. Thomas takes it
that when something is divided into various modes, it is not divided in the same way as a genus is
divided into species. The ten categories are therefore better thought of as the ten different ways in
which things can exist extra animam, rather than as ten kinds of being.
Is being ever predicated univocally?27
Given that being is not a genus divided into the ten categories, the next question to arise is
whether being can ever be said univocally of two things that are the same in some way. For
24See Wippel 87-90.
25There are texts in which St. Thomas speaks of being as a genus—in these texts, we must conclude that the
term genus is itself being used in an analogical sense.
26See Metaphysics 998b21-27.
27See Wippel 90-93.
Carl: Metaphysics 23
example, are two members of the same genus or of the same species called beings univocally?
St. Thomas’s answer to this question can be articulated at three different levels:
(1) St. Thomas holds that different levels or grades of substance are not beings univocally;
by this he means that incorporeal substances (i.e., the angels) do not share being univocally with
corporeal substances (e.g., you and me). His reasoning for this claim is beyond what we can fully
explain at the present, but it involves his claims about the composition of esse and essence in every
created substance.
(2) Among substances of the same level or grade but of distinct species (e.g., a dog and a
man), St. Thomas holds that once again being is not predicated univocally. Again the reason for
this view is beyond our present attention.
(3) It can also be asked whether or not being is predicated univocally of two substances of
the same species (e.g., of two men). As Msgr. Wippel notes, Thomists have differed historically on
this question: John of St. Thomas rejects analogical predication of being in this case, but Msgr.
Wippel offers reasons for holding that even this predication of being will be analogical.28 If his
view on this point is correct, then it will never be the case that being is predicated univocally of
any two distinct things.
Concluding remarks concerning predicamental analogy
It should be noted that what we have called the predicamental analogy of being—the
analogy according to which being is said of both accidents and of substance—is not the only type
of analogy of being in the thought of St. Thomas, and indeed it is far less commented upon than the
other kind of analogy of being, that which obtains between created being and uncreated being. The
Aristotelian theory according to which being is said primarily of substance and secondarily of
accidents is accepted by St. Thomas in a straightforward way, with relatively little need for
extensive clarification by scholarship. What we will later call the transcendental analogy between
God and creatures requires much more careful consideration.
28See Wippel 93. The reason Msgr. Wippel offers is that St. Thomas asserts that esse understood as the act of
existing (actus essendi) is present in only one thing and is only analogically common to two things. But
since being (ens) is understood as what has being (quod habens esse), it follows that ens too can only be
analogically common even to two members of the same species.
Carl: Metaphysics 24
5. Participation
A theme in the thought of St. Thomas that has received much greater attention since the
mid-20th century is that of participation. That the notion of participation deserves sustained
attention should be clear simply from the frequency with which St. Thomas employs the language
of participation in his writings.29 Even if one should conclude that participation is not a notion that
is fundamental to St. Thomas’s metaphysical thought, still one must contend with what St. Thomas
means by the language of participation.
As we shall see, St. Thomas frequently uses the language of participation to express his
doctrine of the real composition of esse and essence in (created) beings. We have not yet addressed
any of St. Thomas’s reasoning in support of this position; for now, our purpose is only to
understand the meaning of this language of participation. Following the presentation of Msgr.
Wippel, we will begin by considering what St. Thomas means by participation in general, with a
quick consideration of St. Thomas’s attitude towards the Platonic theory of participation.
5.1. St. Thomas’s Attitude Towards Plato on Participation
The historical background for the notion of participation is primarily Platonic: one finds in
the dialogues of Plato the famous claim that individual sensible realities participate in the eternal,
immaterial Forms. In this way, Socrates is supposed to be a man by his participation in the separate
Form, man-itself. Concerning this theory, in addition to his more substantive critiques, Aristotle is
famously dismissive of the very language of participation (Metaphysics 1.6):
In his Commentary on this text, St. Thomas shifts the blame for not considering the
meaning of participation exclusively onto the Pythagoreans (In Meta. 1.10):
Hoc autem nomen participationis Plato accepit a
Pythagora. Sed tamen transmutavit ipsum.
Pythagorici enim dicebant numeros esse causas
rerum sicut Platonici ideas, et dicebant quod
huiusmodi existentia sensibilia erant quasi
quaedam imitationes numerorum. Inquantum enim
numeri qui de se positionem non habent,
accipiebant positionem, corpora causabant. Sed
quia Plato ideas posuit immutabiles ad hoc quod de
Now Plato took this name of participation from
Pythagoras. But he altered it. For the Pythagoreans
said that numbers are the causes of things, just as
the Platonists [say that] the ideas [are]; and they
said that sensible existents of this kind are certain
imitations of numbers. For insofar as numbers,
which of themselves do not have position, received
position, they caused bodies. But because Plato
held the ideas [to be] immutable in order that there
29Quick searches on the Index Thomisticus reveal that St. Thomas’s use of the language of participation is in
fact more common than his use of the (explicit) language of analogy.
For according to [Plato], it is impossible that there should be a common definition of any one of these
sensible things which are always changing. Such entities, then, he called Ideas or Forms (species); and
he said that all sensible things exist because of them and in conformity with them; for there are many
individuals of the same name because of participation in these Forms. With regard to participation, he
[merely] changed the name; for while the Pythagoreans say that things exist by imitation of numbers,
Plato says that they exist by participation, changing the name. Yet what this participation or imitation of
Forms is they commonly neglected to investigate.
Carl: Metaphysics 25
eis possent esse scientiae et definitiones, non
conveniebat et in ideis uti nomine imitationis. Sed
loco eius usus est nomine participationis. Sed
tamen est sciendum, quod Pythagorici, licet
ponerent participationem, aut imitationem, non
tamen perscrutati sunt qualiter species communis
participetur ab individuis sensibilibus, sive ab eis
imitetur, quod Platonici tradiderunt.
could be science and definitions about them, he did
not agree [with the Pythagoreans] in using the
name of imitation. But in its place he used the
name of participation. But it must be known that
the Pythagoreans, although they posited
participation or imitation, nevertheless they did not
scrutinize how a common species is participated or
imitated by sensible individuals; [but] the
Platonists did treat this.
Whereas Aristotle seems to blame Plato along with the Pythagoreans for failing to
carefully consider the meaning of participation, St. Thomas preserves the Platonists from this
criticism: even if, as we shall see, he sides with Aristotle rather than the Platonists concerning the
reality of separate Forms, and he expresses the Aristotelian position concerning the relationships
between particulars and universals in the language of participation.
5.2. The Meaning of Participation in General
St. Thomas’s most careful presentation of the meaning of participation is found in his
Commentary on the De Hebdomadibus of Boethius, lec. 2.30 He begins with an etymological
explanation of the meaning of participare:
Est autem participare quasi partem capere. Et ideo
quando aliquid particulariter recipit id quod ad
alterum pertinet universaliter, dicitur participare
illud, sicut homo dicitur participare animal quia
non habet rationem animalis secundum totam
communitatem; et eadem ratione Sortes participat
hominem.
But to participate is, as it were, to take a part. And
therefore when something receives in a particular
way that which belongs to another in a universal
way, it is said to participate that, as man is said to
participate animal since [man] does not possess the
intelligible content of animal according to [its]
entire community; and in the same way Socrates
participates man.
To participate is “to take a part” of something, to receive and possess in a particular or
partial way what belongs to something else in a universal or total way. Consequently, a species
is said to participate (in) its genus, and an individual is said to participate (in) its species (and its
various genera). When it is said that a species participates its genus and that an individual
participates a universal, in both cases we can take this to mean that the former does not exhaust the
intelligible content of the latter. For example, man is but one particular kind of animal.
Consequently, there are things belonging to animal taken as a universal whole (namely, the things
belonging to non-human animals according to their differentiating characteristics) that do not
30It is worth noting that Boethius, in general, was committed to the harmony between the thought of Plato
and the thought of Aristotle. He expresses this view early in the Consolation of Philosophy, and he
characterizes the defense of this view as a central aim of his own philosophical exertions.
Carl: Metaphysics 26
belong to man. Similarly, Socrates does not exhaust the intelligible content of humanity; by being
this man, with this flesh and these bones, Socrates is one limited instantiation of the universal man.
Now, because the distinction between man and animal and the distinction between
Socrates and man are logical or intentional distinctions, this participation of a species in its genus
or of a particular in a universal can be rightly characterized as a logical or intentional participation
rather than as an instance of real participation.31
To summarize, to receive in a particular way what belongs to something else in a universal
way is the general meaning of the term participation for St. Thomas, and it is exemplified by the
participation of a species in its genus and of a particular in the universal. St. Thomas then extends
the meaning of participation to a second set of cases, which involve composition:
Similiter etiam subiectum participat accidens et
materia formam, quia forma substantialis vel
accidentalis, que de sui ratione communis est,
determinatur ad hoc vel illud subiectum.
And similarly, a subject participates [its] accident
and matter [participates its] form, since a
substantial or accidental form, which is common
from its intelligible content, is determined to this
or that subject.
A subject—i.e., a substance—is said to participate (in) its accident, and matter participates
(in) form. These are both instances of composition that we will treat in greater detail later in the
course, in our consideration of the various ways in which ens commune is composite. As we will
see in these later treatments, St. Thomas will analyze both subject-accident composition and
matter-form composition as the composition of a principle of potency with an actualizing principle.
Again, what is fundamentally at issue in calling these cases participation is that the receiving
subjects—substance and matter—do not share in the character of the forms that they receive in an
exhaustive way. Because these examples of participation concern instances of real composition,
one can refer to this as real (or ontological) participation rather than logical participation—
although the claim that these are instances of real composition is something we will defend later in
the course.
Now, one might ask what the relationship is between the participation of an individual in a
universal and the participation of matter in form, since there seem to be examples that are closely
related: Socrates participates in man, and the matter of Socrates participates in the form or nature
of humanity. In the Commentary on the Metaphysics 1.10, immediately prior to the comments
about Pythagoras and Plato that we cited earlier, St. Thomas makes the following remarks:
Individuum autem est homo per participationem,
inquantum natura speciei in hac materia designata
participatur. Quod enim totaliter est aliquid, non
participat illud, sed est per essentiam idem illi.
Quod vero non totaliter est aliquid habens aliquid
aliud adiunctum, proprie participare dicitur. Sicut
But the individual is man by participation, insofar
as the nature of the species is participated in this
designated matter. For that which is something in a
total way, does not participate that [something], but
is that same thing by essence. But what is
something not totally, [rather] having something
31See Wippel 97 and his reference to Fabro and Geiger in n. 9 for this point.
Carl: Metaphysics 27
si calor esset calor per se existens, non diceretur
participare calorem, quia nihil esset in eo nisi
calor. Ignis vero quia est aliquid aliud quam calor,
dicitur participare calorem.
else joined [to it], is properly said to participate.
For example, if heat were a heat existing per se, it
would not be said to participate heat, since there
would be nothing in it but heat. But fire, since it is
something other than heat, is said to participate
heat.
The context for these remarks is that St. Thomas is presenting, so far as possible, the
Platonic account of participation in separate Forms in a positive light. We will return to this text in
its complete context later when we discuss the principle of individuation (the designated matter
that St. Thomas refers to in this text). For now, I only want to highlight that St. Thomas grounds
the participation of the individual in the universal in the participation of matter in form: the former
logical or intentional participation is grounded in a real participation and a real composition. For
this reason, here St. Thomas characterizes participation in the proper sense as the characteristic of
something that is joined to (i.e., composed with) something else.
We should also highlight as important the contrasting of what is per participationem with
what is per essentiam: one will find that St. Thomas frequently makes appeal to this distinction in
his writings.
Returning to our consideration of the Commentary on the De hebdomadibus, lec. 2, St.
Thomas then adds a third use of the term participation:
Et similiter etiam effectus dicitur participare suam
causam, et precipue quando non adequat virtutem
suae causae, puta si dicamus quod aer participat
lucem solis quia non recipit eam in claritate qua est
in sole.
And similarly too an effect is said to participate its
cause, and especially when [the effect] is not equal
to the power of its cause, as for example if we say
that air participates the light of the sun, since it
does not receive [light] with the brilliance it has in
the sun.
When something receives from its efficient cause a perfection that belongs to that cause,
but it receives that perfection in a limited or determinate way relative to the more complete
existence of that perfection in the cause, then that thing can be said to participate (in) the perfection
of the cause. St. Thomas does not offer any elaboration on this third case of participation, but it is a
usage that we will want to recall later.
To summarize, these are the cases or kinds of participation described by St. Thomas:
1) the participation of a species in a genus or of an individual in a species
2) the participation of substance in accident and of matter in form
3) the participation of an effect in its cause
5.3. Participation and Being
Conveniently enough, in the very text that we have considered as a source for St. Thomas’s
understanding of the notion of participation, St. Thomas is concerned with commenting on remarks
made by Boethius about participation and being. We can address ourselves to two questions in
Carl: Metaphysics 28
order: (1) does being participate in anything? (2) In what sense can beings (entia) be said to
participate in being (esse)? We will not at this time address either of these questions in full detail.
As mentioned before, some of the following comments will presume St. Thomas’s thesis that there
is real composition of essence and esse in created beings—this thesis will be considered as our
next major topic in this course.
To begin, it will be helpful to consider the text of Boethius about which St. Thomas is
commenting. The numbers here indicate the numbers of the seven axioms presented by Boethius:32
Does being participate in anything?
As we have seen before, one can understand being as that-which-is (id quod est, ens) or as
the existence or being (esse) that is the act of an essence. We find this very distinction articulated
in the first axiom of Boethius: esse and id quod est are diverse. St. Thomas comments on this
distinction as follows:
Dicit ergo primo quod diversum est esse et id quod
est, quae quidem diversitas non est hic referenda
ad res de quibus adhuc non loquitur, sed ad ipsas
rationes seu intentiones. Aliud autem significamus
per hoc quod dicimus esse et aliud per id quod
He says first therefore that esse and id quod est are
diverse, which diversity is not here referred to the
realities, of which he has not yet spoken, but to the
notions or intentions themselves. But we signify
one thing when we say esse and another when we
32The translation here is a translation of the text of Boethius as found in the Leonine edition of St. Thomas’s
Commentary. The translation is that of Janice Schultz and Edward Synan in their An Exposition of the
“On the Hebdomads” of Boethius (Washington, DC: The Catholic University of America Press, 2001),
xxxi & 15.
(1) Being (esse) and that-which-is (id quod est) are diverse. For being itself (ipsum esse) as yet is not.
That-which-is, however, once the form of being has been taken on, is and stands together.
(2) What-is (quod est) can participate in something, but being itself (ipsum esse) in no way participates
in anything. For participation occurs when something already is. Something is, however, when it has
received being (esse).
(3) That-which-is can possess something other than what it itself is. Being itself, however, has nothing
else outside itself as an admixture.
(4) However, to be something, and to be something in this, that [a thing] is, are diverse. For by the
former, accident is signified; by the latter, substance.
(5) Everything that is (omne quod est) participates in that which is being (eo quod est esse) with the
result that it be (ut sit). It participates in something else with the result that it be something. And
through this, that-which-is participates in that which is being with the result that it be. It is, however,
with the result that it can participate in anything else whatever.
(6) In every composite, being (esse) is other than the item itself. Every simple item possesses its being
(esse) and that-which-is (id quod est) as one.
(7) All diversity is discordant, whereas similitude must be sought. And what seeks something else is
shown to be itself by nature such as that which it seeks.
What we have set down as preliminaries, therefore, suffice. Each one will be applied in argumentation
by the prudent interpreter of their meaning.
Carl: Metaphysics 29
dicimus id quod est, sicut et aliud significamus
cum dicimus currere et aliud per hoc quod dicitur
currens. Nam currere et esse significatur in
abstracto sicut et albedo; sed quod est, id est ens et
currens, significatur in concreto velut album.
say id quod est, just as we also signify one thing
when we say “to run” and another when we say
“running.” For to run and to be (esse) are signified
in the abstract, like whiteness; but what is, that is, a
being (ens) and [one] running, are signified in the
concrete, like white [thing].
The distinction between esse and id quod est or ens is not initially to be construed as a real
distinction, but instead should be construed as a distinction in notion or intention—i.e., as a logical
distinction. Similarly, one can draw a logical distinction between “one running” and “to run,” or
between “white thing” and “whiteness,” as between the concrete and the abstract. Considered in
this way, therefore, the distinction between ens and esse is just the logical distinction between an
existent in the concrete and existence in the abstract.
Given this distinction between esse and id quod est, the question of whether being
participates in anything can therefore be understood in two ways: (a) Does esse participate in
anything? (b) Does that-which-is participate in anything?
Does esse participate in anything?
In his Commentary, following the preceding elaboration of the distinction between esse
and id quod est, St. Thomas immediately comments on the question of whether esse participates
anything:
Deinde cum dicit: Ipsum enim esse etc., manifestat
praedictam diversitatem tribus modis.
Quorum primus est quia ipsum esse non
significatur sicut subiectum essendi, sicut nec
currere significatur sicut subiectum cursus. Unde
sicut non possumus dicere quod ipsum currere
currat, ita non possumus dicere quod ipsum esse
sit; sed id quod est significatur sicut subiectum
essendi, velut id quod currit significatur sicut
subiectum currendi; et ideo sicut possumus dicere
de eo quod currit sive de currente quod currat in
quantum subicitur cursui et participat ipsum, ita
possumus dicere quod ens sive id quod est sit in
quantum participat actum essendi.
Then when he says: For being itself, etc., he shows
the aforementioned diversity in three ways.
Of these, the first is that being (esse) itself is not
signified as the subject of being, as “to run” is not
signified as the subject of running. Wherefore, just
as we cannot say that “to run” itself runs, so we
cannot say that being (esse) itself is; but that which
is (id quod est) is signified as the subject of being,
just as that which runs is signified as the subject of
running; and therefore just as we can say of that
which runs or of the runner that he runs insofar as
he is the subject of running and participates it, so
we can say that being (ens) or that which is (id
quod est) is insofar as it participates the act of
being (actus essendi).
Given only the logical distinction between ens and esse as the distinction between the
concrete and the abstract, it cannot be said that esse participates ens; rather, ens participates esse
insofar as it is the subject of esse, just as the runner is the subject of and participates running, rather
Carl: Metaphysics 30
than vice versa. St. Thomas proceeds to explain that it is for this reason that Boethius next says
being itself as yet is not (ipsum esse nondum est): ens is, because ens is the subject of esse, but esse
is not the subject of anything, and so it cannot be said that esse is any more than it is said that to
run runs.
After providing the threefold explanation of the notion of participation that we considered
above, St. Thomas proceeds to offer more comments concerning the (im)possibility that esse
should participate in anything:
Praetermisso autem hoc tertio modo participandi,
impossibile est quod secundum duos primos
modos ipsum esse participet aliquid. Non enim
potest participare aliquid per modum quo materia
vel subiectum participat formam vel accidens quia
ut dictum est ipsum esse significatur ut quiddam
abstractum. Similiter autem nec potest aliquid
participare per modum quo particulare participat
universale; sic enim etiam ea quae in abstracto
dicuntur participare aliquid possunt sicut albedo
colorem, sed ipsum esse est communissimum,
unde ipsum quidem participatur in aliis, non autem
participat aliquid aliud.
But this third mode of participating set aside, it is
impossible that being (esse) itself participate
something according to the first two modes. For it
cannot participate something through the mode by
which matter or a subject participates form or
accident, since as was said being (esse) itself is
signified as something abstract. Nor similarly can
it participate something through the mode by
which a particular participates a universal; for in
this way too those things which are said in the
abstract can participate something, as whiteness
participates color, but being (esse) itself is most
common, indeed such that it is participated by
others, but it does not participate something else.
Without commenting at this moment on the third mode of participation, St. Thomas
excludes the first two modes of participation with regard to esse itself as that which participates.
However, in his explanation, he has noted that esse is most common (communissimum), with the
consequence that other things participate in esse, but esse does not participate in anything else.33
Does that-which-is participate in anything?
Thus, it will come as no surprise that St. Thomas defends the view that that-which-is does
participate in something else. First, and most importantly, it can be said that ens participates in
esse. Our purpose for now is to sketch only a general sense in which such a claim may be
articulated: fuller clarity about participation in esse will come only after we have discussed the real
composition of essence and esse in created substances and the existence of God, to Whom St.
Thomas will refer as ipsum esse per se subsistens.34 St. Thomas continues, in the text we have been
studying as follows:
33As we will discover later, this is a way of saying that esse is a transcendental term. St. Thomas often refers
to the transcendentals as the communissima.
34It must suffice for now to note that the qualification per se subsistens serves to distinguish the divine esse
from ipsum esse in the sense of esse commune (the act of [created] being in general). Esse commune is
signified in the abstract, as something that is not per se subsistens.
Carl: Metaphysics 31
Sed id quod est sive ens, quamvis sit
communissimum, tamen concretive dicitur, et ideo
participat ipsum esse, non per modum quo magis
commune participatur a minus communi, sed
participat ipsum esse per modum quo concretum
participat abstractum. Hoc est ergo quod dicit quod
id quod est, scilicet ens, participare aliquo potest;
sed ipsum esse nullo modo participat aliquo; et
hoc probat ex eo quod supra dictum est, quod
scilicet ipsum esse nondum est. Manifestum est
enim quod id quod non est non potest aliquo
participare, unde consequens est quod participatio
conveniat alicui cum iam est; sed ex hoc aliquid
est quod suscipit ipsum esse sicut dictum est. Unde
relinquitur quod id quod est aliquid possit
participare, ipsum autem esse non possit aliquid
participare.
But that-which-is or being (ens), although it is
most common, nevertheless is said concretely, and
therefore it participates being (esse) itself, not
through the mode by which the more common is
participated by the less common, but [that-whichis] participates being (esse) itself through the mode
by which the concrete participates the abstract.
This, therefore, is what he says, that that-which-is,
namely being (ens), can participate in something;
but being (esse) itself in no way participates in
anything; and he proves this from what was said
above, namely that being (esse) itself as yet is not.
For it is manifest that that-which-is-not cannot
participate in anything, whence it follows that
participation belongs to something when it already
is; but something is by this that it receives being
(esse) itself, as was said. Wherefore, it remains that
that-which-is can participate something, but being
(esse) itself cannot participate anything.
It is important to emphasize that the participation of ens in esse as articulated here
presumes only the logical distinction between the concrete and the abstract: ens participates esse
just as a runner participates in “to run,” and a white thing participates in whiteness. As St. Thomas
is careful to point out, the participation of ens in esse is not even a case of participation of the less
common in the more common, because both ens and esse are communissimum, most common.
Nevertheless, as we shall see in consideration of our next major topic (real composition of essence
and esse in created substances), St. Thomas is here paving the way for an argumentation for a real
distinction rather than a merely logical distinction between that-which-is and esse itself.
We will comment more in a moment on the claim that that-which-is (ens) can be said to
participate being (esse). For now, we should note another sense in which ens is said to participate
in something. We have already observed that a substance can be said to participate an accident.
According to the analogical character of ens, which is predicated primarily of substance, the
participation of substance in accident is the participate of ens in something. St. Thomas speaks
about substance-accident participation as the participation of ens in something later in the same
text we have been considering at length, Exp. De heb. lec. 2.
First, it should be noted that just as St. Thomas characterizes the participation of ens in
esse at first according to the participation of the concrete in the abstract, so too does he note that
human participates humanity and that white participates whiteness.
Ex hoc autem quod homo habet humanitatem vel
album albedinem, non prohibetur habere aliquid
But from this that man has humanity or white
whiteness, it is not precluded [that it] have
Carl: Metaphysics 32
aliud quod non pertinet ad rationem horum, nisi
solum quod est oppositum hiis; et ideo homo et
album possunt aliquid aliud habere quam
humanitatem vel albedinem; et haec est ratio quare
albedo et humanitas significantur per modum
partis et non praedicantur de concretis sicut nec
aliqua pars de suo toto. Quia igitur, sicut dictum
est, ipsum esse significatur ut abstractum, id quod
est ut concretum, consequens est verum esse quod
hic dicitur quod id quod est potest aliquid habere
praeter quam quod ipsum est, id est praeter suam
essentiam, sed ipsum esse nihil aliud habet
admixtum praeter suam essentiam.
something other that does not pertain to the
intelligible content of these, except only that which
is opposed to these; and therefore man and white
can have something other besides humanity or
whiteness; and this is the reason why whiteness
and humanity are signified in the manner of a part
and are not predicated of concrete [items], just as a
part [is] not [predicated] of its whole. Since
therefore, as was said, being (esse) itself is
signified as abstract, [and] that-which-is as
concrete, it follows that what is said here is true,
that that-which-is can have something other than
what it itself is, that is, outside its essence, but
being (esse) itself has nothing else admixed outside
its essence.
This possibility of ens receiving something not contained in its own essence is articulated
in two ways by St. Thomas: (1) in terms of the reception of esse, which is not contained in the
content of a thing’s essence; and (2) in terms of the reception of an accident, which is also not
contained in the content of a thing’s essence. To discuss the first kind of reception by ens of
something not contained in its essence will be the next major topic of discussion—the real
composition of essence and esse—to which we will turn shortly. For now, we want to consider the
participation of ens in accident, which St. Thomas considers in the same text:
Si vero sit talis forma quae sit extranea ab essentia
habentis eam, secundum illam formam non dicitur
habens esse simpliciter, sed esse aliquid, sicut
secundum albedinem homo dicitur esse albus. . . .
Dicit quod ad hoc aliquid sit simpliciter subiectum
participat ipsum esse, sed ad hoc quod sit aliquid,
oportet quod participet aliquo alio, sicut homo ad
hoc quod sit albus participat non solum esse
substantiale sed etiam albedinem.
But if the form be such that it is extraneous to the
essence of what possesses it, according to that
form it is not called something having being
(habens esse) without qualification, but [something
having] to-be-something (esse aliquid), as
according to whiteness man is said to be white. . . .
He says that for this that something be a subject
without qualification it participates being (esse)
itself, but for those that it be something, it is
necessary that it participate something else, as
man, for this that he be white, participates not only
substantial being (esse) but also whiteness.
The participation of a substance in accident is thus a kind of participation of ens or id quod
est in something else, because it does not pertain to this or that subject to include in its essence this
Carl: Metaphysics 33
or that accidental characteristic. In this way, then, ens can be said to participate in something.
To summarize, then, ens or that-which-is can be said to participate in two general ways: it
participates in esse, and it participates in accident. With regard to the former, so far we have
articulated only a logical or intentional way in which ens participates esse: we will now turn to the
distinct senses in which the participation of ens in esse can be understood.
In what distinct senses can beings (entia) be said to participate being (esse)?
We have already indicated that ens participates esse as the concrete participates the
abstract, just as white participates whiteness. So, it will be no surprise at this point that St. Thomas
does affirm that beings (entia) participate being (esse). However, by such an expression St.
Thomas typically means more than just the expression of a logical or intentional distinction
between the concrete being and its act of being taken in the abstract (which can be compared to the
concrete runner and his act of running taken in the abstract). We will here comment briefly on a
subject to which Msgr. Wippel devotes considerable attention (pp. 110-24): what does it mean to
say that beings participate esse? Following Msgr. Wippel’s presentation, we can distinguish three
senses in which this claim can be taken. Because the following comments will presuppose both the
real composition of essence and esse in finite realities and the existence of God, Who is ipsum esse
per se subsistens, what we are considering can be said to be usages of the phrase “participation in
esse” that will only be justified by virtue of arguments that will be given later in the course.35
(1) To participate in esse can be understood as to participate in esse commune, which is
esse understood as an analogically common perfection in which all finite or composite realities
share. This esse commune is not to be identified with God; rather, as will be discussed later in the
course, esse commune is caused by God. When we say that esse commune is an analogically
common perfection, we mean to exclude that esse commune be understood as a separate form
distinct from the individuals that participate it. That is, esse commune is not a Platonic Form.
Rather, each concrete ens possesses its own esse or act of existence, and insofar as one considers
esse to be a perfection shared in common, one calls this esse commune.
(2) To participate in esse can be understood as to participate in ipsum esse per se
subsistens, that is, in divine esse. This is not St. Thomas’s preferred mode of expression, but he
does speak in this way on occasion. This can only be understood as the participation of an effect in
its cause: one must exclude any notion that the divine esse itself is somehow communicated or
diversified in created beings. As Msgr. Wippel details, for this reason more often says that finite
beings participate a likeness of the divine esse, by which he means that they participate their own
esse, which is caused by and bears some likeness to the divine esse. Alternatively, St. Thomas will
say that beings participate esse from God. As Msgr. Wippel notes, the participation of beings in
esse commune is therefore ultimately grounded in their participation in divine esse, understood as
the participation of an effect in its cause.
(3) A being can be said to participate in esse insofar as it participates its own act of
existence: this is like the participation in esse commune, but one considers this concrete being’s act
of existence in particular rather than considering esse as a perfection that is analogically common
to many. What does it mean to say that this being participates its own actus essendi? The answer to
this question can only be given by answering a much more difficult question, to which we will
given only limited attention in this course: What is it that accounts for the limited or finite
character of a created reality? The claim that a finite being participates its own actus essendi can be
well understood, if one accepts the claim that it is primarily a thing’s essence rather than its esse
35See Msgr. Wippel’s summary remarks on pp. 120-21.
Carl: Metaphysics 34
that should be taken as the principle according to which it is finite and limited.36
36For Msgr. Wippel’s preliminary remarks on this point of dispute, see pp. 124-31.
Carl: Metaphysics 35
6. Real Composition of Essence and Esse in Finite Beings
Having noted that being in general (ens commune) is a common subject of study according
to analogical rather than univocal unity, we can proceed to a consideration of ens taken in its
primary referent, which is substance. What the predicamental analogy of being allows us to do, in
our consideration of ens commune (the subject of metaphysics), is to justify this initial focus on
substance. Because of the analogy of being, we understand that whatever we say about substance
will have implications for what we will say about accidents.
The central note of St. Thomas’s analysis of finite being, and particularly of substance, is
that finite being is composite, in various ways. We will begin with what is perhaps St. Thomas’s
most famous metaphysical thesis, the real distinction and composition of esse and essence in finite
beings.
6.1. Background: Relation of Concepts to Reality; Real and Logical Distinction
Medieval philosophers and theologians generally recognized a distinction between esse
(existence) and essence in created things, but it was a matter of significant dispute whether this
distinction is a real distinction or merely a logical or conceptual distinction. That is, is this
distinction between esse and essence a real feature of the world even apart from the consideration
of the mind? Or is it a distinction that only exists in the mind, in the way that (for example) the
distinction between dog and animal is a logical distinction that is not really present in a dog?37
To understand the question posed, we should draw two related distinctions. First, St.
Thomas distinguishes between three ways in which a concept of the intellect can be related to
things outside the mind, as follows:38
(1) What is conceived by the intellect can be a similitude (i.e., a likeness) of something
existing outside the mind. For example, one’s concept of man is a likeness of a thing existing
outside the mind, that is, of a man. Such a concept has an immediate foundation in the thing
outside the mind, insofar as the concept of man is a likeness of the essence of man; and this
likeness comes to exist as the product of the act of understanding.39
(2) What is conceived by the intellect is sometimes not a likeness of anything outside the
mind, but is rather something that arises from the activity of understanding. For example, the
concept of a genus is not a similitude of anything existing outside the mind; rather, it is a concept
that arises is consideration of the relationship between the essence animal and the various kinds of
things that possess this essence. The concept of genus has its foundation in things outside the mind;
this is not an immediate foundation, but a remote foundation. (These intentions, such as genus or
species, are typically called second intentions, as distinguished from first intentions, which are
concepts of the first kind distinguished above.)
(3) Finally, what is conceived by the intellect can fail to be a likeness of anything outside
37That is, in reality, a dog is not “composed” of animal and dog. This can be recognized from the fact that the
ratio of dog includes the ratio of animal.
38In Sent. 1.2.1.3.
39It should be noted that the concept taken in this sense is distinct from the intelligible species that is
abstracted from the phantasm. The intelligible species is the formal principle of the act of understanding,
whereas the concept is the terminus or product of the act of understanding. Both the intelligible species
and the concept are likenesses of the thing outside the mind, but one does not possess any awareness of
an intelligible species, while one is aware of one’s concept.
Carl: Metaphysics 36
the mind, such as the concept of a chimera. Such a concept has no foundation except the mind
itself.
Now, one can also draw a related distinction between two kinds of distinction: this is the
distinction between a real distinction and a distinction of reason.
(a) In a real distinction, one distinguishes two items that are distinct in reality even apart
from the consideration of the mind, because the two items are not identical in reality. For example,
a man is really distinct from a dog, even prior to the consideration of the mind. This is obviously a
case of a real distinction, because a dog and a man possess independent existence as substances.
(b) In a distinction of reason (or a logical or conceptual distinction), one draws a
distinction between things that are not absolutely distinct apart from the consideration of the mind.
That is, one considers a single thing according to distinct concepts. An obvious example of a
distinction of reason is the distinction between the morning star and the evening star (which are
identical in reality: they are both the planet Venus). St. Thomas will also say (as we will see later in
our course) that the divine attributes are not really distinct but are only distinct according to reason.
Indeed, the texts where St. Thomas brings up the difference between real and logical distinction are
almost exclusively concerned with theological questions: he affirms on the one hand that the
distinction between the divine Persons is a real distinction40, whereas the distinction between the
divine attributes is a distinction of reason.41
A number of later authors (such as Ockham) will understand real distinction exclusively as
the distinction between one thing (res) and another thing (res) which exist or can exist
independently from one another, such as a man and a dog or a man and his arm. If this is what is
meant by a real distinction, then a real distinction always implies the possible separate existence of
the items distinguished. This is not, however, how St. Thomas understands a real distinction: it is
not a requirement for a real distinction that the items distinguished be capable of existing
independently from one another.
For example, as we will explain below, for St. Thomas the distinction between substantial
form and prime matter is a real distinction, because these are two principles that enter into real
composition in a corporeal substance: but neither the matter nor the form is capable of existing
independently of the composite. (The only exception to this is the human soul, which is a
substantial form that survives the corruption of the human substance.) Substantial form and matter
are really distinct, according to St. Thomas’s understanding of real distinction, despite the fact that
neither the substantial form (except for the human soul) nor the prime matter is capable of
independent existence as a thing.
Much of the controversy about whether the distinction between essence and esse is a real
distinction or only a distinction of reason hinges on what one understands as the implications of a
real distinction with regard to the possible independent existence of the items distinguished.
Therefore, when we argue that essence and esse are really composite and really distinct in created
things, we do not mean to imply (absurdly) that an essence could exist apart from its esse.
6.2. Argument for Real Composition of Essence and Esse
One can distinguish in St. Thomas’s writings a variety of ways of arguing for the claim that
40See In Sent. 1.2.1.5.
41See In Sent. 1.2.1.3.
Carl: Metaphysics 37
esse and essence are really distinct and composite in finite beings. With our limited time, we will
begin by considering St. Thomas’s comments concerning real composition in the context of the
long text to which we have given significant attention under the heading of participation, Exp. De
heb., lec. 2. In this place, St. Thomas writes:
Deinde cum dicit: Omni composito etc., ponit
conceptiones de composito et simplici, quae
pertinent ad rationem unius, et est considerandum
quod ea quae supra dicta sunt de diversitate ipsius
esse et eius quod est, est secundum ipsas
intentiones. Hic ostendit quomodo applicetur ad
res; et primo ostendit hoc in compositis, secundo
in simplicibus, ibi: Omne simplex etc.
Est ergo primo considerandum quod sicut esse et
quod est differunt secundum intentiones, ita in
compositis differunt realiter. Quod quidem
manifestum est ex praemissis. Dictum est enim
supra quod ipsum esse neque participat aliquid ut
eius ratio constituatur ex multis, neque habet
aliquid extrinsecum admixtum ut sit in eo
compositio accidentalis; et ideo ipsum esse non est
compositum; res ergo composita non est suum
esse; et ideo dicit quod in omni composito aliud est
esse ens et aliud ipsum compositum quod est
participando ipsum esse.
Then when he says: In every composite etc., he
posits conceptions about the composite and the
simple, which pertain to the character of unity, and
it must be considered that those things said above
about the diversity of being (esse) itself and of
what-is (quod est), is according to the intentions
themselves. Here he shows how [this] is applied to
things; and first he shows this about composites,
second about simples, where [he says]: Every
simple etc.
Therefore first it must be considered that just as
being (esse) and what is (quod est) differ according
to intention, so also in composite [things] they
differ really. Indeed this is manifest from what
preceded. For it was said above that being (esse)
itself neither participates anything as though its
ratio were constituted from many, nor does it have
something extrinsic admixed with it as though
there were in it accidental composition; and
therefore being (esse) itself is not composite;
therefore a composite thing is not its esse; and
therefore he says that in every composite it is one
thing to be a being (esse ens) and another to be the
composite itself, which is, by participating ipsum
esse.
The most famous text concerning the distinction of essence and esse, that found in c. 4 of
the De ente et essentia.42 We can distinguish two stages in the argument presented in this text. The
first stage presents a version of what is often called St. Thomas’s intellectus essentiae
(understanding of an essence) argument. The context of this passage is that St. Thomas is
commenting on the characteristics of simple, intelligible essences (i.e., angels).43
42See Wippel 137-150 for
43All quotations are from the Goodwin translation.
Carl: Metaphysics 38
Stage 1: intellectus essentiae argument
Even though intelligences are simple (or non-composite) insofar as they are not composed
of matter and form, nevertheless St. Thomas wants to argue that there is some potency in them,
such that they are not pure act. (As we will explain later, St. Thomas holds that God alone is
absolutely pure act without any admixture of potency). St. Thomas now begins to offer his
argument for the claim that intelligences are composite in some way:
St. Thomas’s argument begins with the assertion that a given essence includes as
intelligible parts all of those things without which that essence cannot be understood. For example,
rational, animal, flesh, and bones are all intelligible parts of the essence of man: one does not
understand what a man is without knowing these parts of the essence. Anything that belongs to a
particular man besides these essential notes does so because of some kind of composition with
something extraneous to the essence of man. For example, that a man is white or tall or educated is
a matter of composition with these accidental forms.
Now St. Thomas notes that the esse of a thing is not one of these intelligible parts of an
essence, because one can understand what an essence or quiddity is without having an
understanding of its existence. One can know what a man is or what a phoenix is without knowing
whether these essences exist. Therefore esse is not a part of the essence of either of these things,
and in general St. Thomas reaches the conclusion that esse is not a part of any essence of which
human beings have some understanding.
Concerning the phoenix
What are we to take St. Thomas to mean by this example of the phoenix? One common
way of interpreting this passage is to treat the phoenix as an instance of a chimera, that is, of a
possible essence that does not actually exist. On this reading, St. Thomas is asserting that one can
understand the essence of something that does not, never has, and never will actually exist.
Understanding St. Thomas’s example in this way, a number of commentators have offered the
criticism that it seems problematic to say that we can possess understanding of such a non-existent
possible essence. It seems impossible that we should know the essence of a thing that does not
exist. Furthermore, it seems problematic to reason from an assertion about the understanding of
On the other hand, every essence or quiddity can be understood without its esse being understood.
I can understand what a man or phoenix is, and yet not know whether or not it exists in the nature
of things. Therefore, it is evident that the act of existing is other than essence or quiddity.
Although substances of this kind are simply forms without matter, nonetheless they are not in
every way simple, as pure acts are. They do have an admixture of potency, which is evident in the
following way.
Whatever is extraneous to the concept of an essence or quiddity is adventitious, and forms a
composition with the essence, since no essence can be understood without those things which are
its parts.
Carl: Metaphysics 39
non-existent possibles to a claim about the metaphysical structure of real being.
We can articulate the problem posed by this interpretation in terms of Aristotle’s scientific
questions, which are treated at the beginning of Posterior Analytics II.
(1) an est – if it exists / does the subject exist / whether it is
-The first scientific question concerns whether the subject to be studied exists.
Typically, in the case of the chief sciences, this question is answer not by
argument, but immediately from sense experience.
-In order to answer this question, one must first possess a nominal understanding
of what the thing in question is: that is, one must understand what the thing’s name
signifies.
(2) quid est – what is it / what is the essence or quiddity
-The second scientific question concerns the essence or quiddity of the subject
studied. The answer to the question quid est is expressed through terms that can be
essentially predicated of the subject (i.e., genera, species, and difference), and most
properly through the real definition of its species.
-Aristotle and St. Thomas both emphasize that once one knows that something
exists (answering an est affirmatively), one always asks what it is (quid est).
Furthermore, they also claim that one must know that something exists before one
can reasonably inquire into what it is, in this strict sense. This requirement is
grounded in their epistemological thesis that all human knowledge is derived
ultimately from the senses.
[(3) utrum est / quia – whether it is such and such / that it is so
-The third scientific question concerns the predication of something about the
subject studied. That is, this question possesses a more complex structure than the
first two questions. One can best understand this question as pertaining to the
properties of the subject, as distinct from its essence, which is expressed in the
definition as an answer to the question quid est.
(4) propter quid – why is it such and such
-The fourth question is the proper question of science in the strict sense: it is the
question answered by the demonstration, in which one expresses in a syllogism the
relationship of cause to effect, answering why it is that a subject possesses a
property (the answer to the question utrum est) with an argument that employs the
essence of the subject (the answer to quid est) as a middle term.]
The example of the phoenix, if interpreted as a chimera (i.e., as something that never
actually exists but that only exists as a being of reason), suggests that we could know the answer to
the question quid est without having previously established an affirmative answer to the question
an est. It seems much more reasonable to say that while we may know what the name phoenix
signifies (i.e., a mythical bird, of which there is only one, that is consumed by fire at death and is
later reborn from the ashes), this does not count as quidditative knowledge (i.e., as a grasp of what
the phoenix really is in itself).
However, the example need not be taken in this way at all (i.e., as asserting that we possess
quidditative knowledge of a non-existent entity), given what a phoenix is supposed to be. A
phoenix is a mythical bird possessing the following characteristics: (1) there is only one phoenix;
(2) the phoenix lives for a period of time, and at the end of its life it is consumed by fire and
Carl: Metaphysics 40
reduced to ashes; (3) for a period of time, the phoenix no longer exists, until it is reborn from the
ashes.
Although it is not necessarily the case that St. Thomas himself believed that the phoenix is
real, there were many among medieval Christians who did think that the phoenix was real. In any
event, in picking the example of the phoenix, St. Thomas has not selected a mere chimera; he has
selected a chimera that some people thought to be real, and a chimera that has various
characteristics relevant for its use as an example in this context. That is, a phoenix is an animal that
is supposed to exist at some times and not at others; and since there is only one phoenix, if the one
phoenix does not exist, then no phoenix exists.44 Thus one could understand what a phoenix is
without knowing anything about whether it exists. Therefore, St. Thomas concludes, it cannot be
the case that esse is included as an intelligible part of the essence of the phoenix. It seems, then,
more reasonable to think that St. Thomas included the example of the phoenix not insofar as it is a
chimera, but as a supposed essence that at certain times does not exist.
What is established by the first stage of this argument?
Even taking the example of the phoenix as we have just suggested, the question arises as to
what exactly this argument establishes. That the understanding of an essence does not include esse
at a minimum establishes that there is a distinction between essence and esse, between what
something is and its actual existence. However, is this distinction necessarily a real distinction in
an extramental thing, even apart from the consideration of the mind?
On the one hand, it seems that St. Thomas may understand even this first stage of his
argument to establish real composition of essence and esse: he contends that “whatever is
extraneous to the concept of an essence or quiddity is adventitious, and forms a composition with
the essence.” However, many recent Thomistic scholars have called into question whether the
intellectus essentiae argument can truly establish a real distinction and composition between
essence and esse.45 In particular, Msgr. Wippel brings up that St. Thomas is very clear elsewhere in
asserting that we cannot possess quidditative knowledge of separate substances (the subject under
direct examination in this text from the De ente), and he also expresses serious reservations about
our capacity for comprehensively grasping even the quiddities of corporeal substances.46 If we
cannot comprehensively grasp either simple essences or the essences of corporeal substances, then
the fact that esse is not included in our understanding of any essence does not necessarily mean
that esse is not a part of that essence: it may just be that we know that essence (and every essence)
imperfectly. As Msgr. Wippel points out, the intellectus essentiae argument disappears from St.
Thomas’s later writings, and so perhaps St. Thomas himself came to recognize that it could not
establish a real distinction and composition, but only a logical distinction.
Stage 2: the impossibility of more than one being in which essence and esse are the same
Having given an initial argument for the composition and distinction of essence and esse in
44Jean Buridan, a later critic of St. Thomas’s arguments in favor of real distinction of essence and esse,
understands the purpose of the example of the phoenix in the way suggested here; in his analysis of the
intellectus essentiae argument, he replaces the phoenix with the rose and thunder, two realities that exist
only some of the time. I take this comparison between Buridan and St. Thomas from Gyula Klima,
“Parvus Error in Principio Magnus est in Fine,” a paper given at The Metaphysics of Aquinas and the
Modern Retrieval of Medieval Thomism, March 26, New York, NY. The paper’s publication is
forthcoming.
45See Wippel 140-43.
46Wippel 142.
Carl: Metaphysics 41
simple substances, St. Thomas proceeds to a second stage in his argument, in which he
acknowledges the possibility of a being in which essence and esse are not distinct:
That essence and esse are distinct in all things is true unless, perhaps, there is something
whose very quiddity is its esse. If such a thing exists, it would have to be unique and primary (or
first). To argue for this conclusion, St. Thomas offers an account of the various ways in which a
reality can be multiplied.
Ways in which something can be multiplied:
(1) By the addition of a difference, as a genus is multiplied into various species. What
distinguishes the species of a genus are the differences of those species.
(2) By the reception of a form into diverse matter, as a species (such as man) is multiplied
in distinct individuals. (We will examine this claim later, that a species is individuated by matter.)
(3) By being something absolute so as to be distinguished from what is received in
something else. St. Thomas suggests an example: if there were a separate heat that was not the heat
of anything, then it would be distinct from the heat that is an accident of something. However,
there could only be one such separate heat, since nothing would serve to distinguish a separate heat
from another separate heat. St. Thomas’s point with this kind of multiplicity is that two things can
be diverse even without belonging to a common genus or species. (As we will see, this is how St.
Thomas will explain God’s being distinct from other things: He is distinct from other things even
without sharing in a genus or species with them).
St. Thomas then proceeds to explain why a being in which essence and esse are identical
could not be multiplied in any of the ways indicated above.
This is true, unless, perhaps, there is something whose quiddity is its very esse. This thing would
have to be unique and primary, since it would be impossible for anything to be multiplied except
by the addition of some difference, as the nature genus is multiplied into species; or by a form
received in diverse matters, as the nature species is multiplied in different individuals; or by one
being absolute, and the other being received in something. For example, if there were a certain
separated heat it would be distinct, in virtue of its very separation from the heat which is not
separated.
If, however, something is posited which is simply its own act of existence such that it would be
subsistent existence itself, this existence cannot receive the addition of a difference, because then it
would not be simply an act of existing, but an act of existing plus this certain form. Even less
would it receive the addition of matter, because then it would not be subsistent existence, but
material existence. Hence, there remains only one such thing that is its own act of existing.
Carl: Metaphysics 42
It is not possible for the suggested subsistent esse to be multiplied in either of the first two
ways distinguished above. The first way, multiplication by the addition of a difference, is not
possible, because then the essence of the being in question would no longer be simply esse, but
esse plus the difference. (Similarly, a dog is not merely or simply an animal, precisely because its
essence is differentiated from the genus animal.)
The second way, multiplication of a species by reception of form into matter, would
similarly make the suggested subsistent esse to be no longer simply or purely esse, but esse plus
matter. This is an even more difficult suggestion, because then the esse in question would be
material being: but esse is not restricted to material being, as is established by the judgment of
separation.
As for the third way in which something can be multiplied, St. Thomas does not offer any
direct commentary concerning whether this kind of multiplication could occur in the case of
subsistent esse, but implicitly he accepts that subsistent esse would be distinguished from all other
things just be being esse absolutely, while esse in everything else is something distinct from its
essence and received in it. As noted above, this third mode of multiplication allows only for one
instance of the separate and absolute form, and this is precisely what St. Thomas intends to
establish concerning subsistent esse: there can only be one such being. This allows St. Thomas to
conclude his argument in favor of real distinction and composition of essence and esse:
There can be at most one being in which essence and esse are identical, so that its essence
is its very act of existence. In every other thing, esse (understood as the act of existence) and the
essence or quiddity must be distinct. St. Thomas then applies this conclusion to the intelligences,
concluding that in them act of existence must be distinct from form. We can add a point that St.
Thomas makes explicit elsewhere, that the act of existence is related as a principle of actuality to
the essence, which is in potency to receive the act of existence.
Does this argument presuppose God’s existence?
Among those scholars who acknowledge that St. Thomas posits a real distinction and
composition of esse and essence in created things, there is a dispute about whether St. Thomas’s
arguments for this thesis depend upon previously having demonstrated the existence of God. There
is in particular disagreement about the text from the De ente et essentia treated above. As we have
interpreted the argument, it does not depend upon any previously established claim concerning
God’s existence. The suggestion of a being in which essence and esse are identical is, at this point
in the argument, only a hypothetical. Nevertheless, in other contexts (such as Summa contra
Accordingly, in anything other than it, the act of existing must necessarily be other than its
quiddity or nature or form. Hence, among the intelligences, their acts of existing must be other than
their forms.
Carl: Metaphysics 43
Gentiles II c. 52, which Msgr. Wippel treats in his book, pp. 151-53), St. Thomas does take God’s
existence for granted (and the identity of essence and esse in God) in arguing for the real
distinction and composition of essence and esse in creatures.
6.3. The Suggestion of God’s Existence from the Real Composition of Essence and Esse
Not only is it the case that the argument for real distinction given in the De ente et essentia
c. 4 does not presume God’s existence; instead, St. Thomas uses the distinction between essence
and esse in creatures in order to immediately offer a brief argument for the existence of God:
This section of the De ente et essentia (which Msgr. Wippel also calls the third stage of the
argumentation concerning essence and esse) presents an argument for the existence of the being in
which essence and esse are identical. The argument proceeds from the assertion that whatever a
thing has must be caused either by the intrinsic principles of the thing or by some extrinsic agent. If
this assertion is accepted, then it follows that whatever has esse (the act of existing) but is not
identical with it must have its esse caused by something, either by its own intrinsic principles or by
an extrinsic agent. But it is impossible that a thing’s esse should be caused by its intrinsic
principles, because then a thing would be the cause of its own existence, which is absurd, because
something must exist in order to be a cause.47 It remains, then, that anything in which essence and
47St. Thomas clarifies that this claim about causing existence is restricted to efficient causality, because he
Whatever belongs to something is either caused by the principles of its nature, like risibility in
man, or accrues to it from some extrinsic principle, like the light in the air, which is caused by the
sun. It is impossible that the act of existing itself be caused by the form or quiddity—and by
“caused” I mean as by an efficient cause—for then something would be the cause of itself and
produce itself in existence, which is impossible. It is therefore necessary that everything whose act
of existing is other than its nature have its act of existing from another. And because everything
which exists through another is reduced to that which exists through itself, as to a first cause, there
must be something which causes all things to exist, inasmuch as it is subsistent existence alone.
Otherwise we would proceed to infinity in causes, since everything which is not a subsistent act of
existing has a cause for its act of existing, as we have just said. It is evident, therefore, that an
intelligence is a form and an act of existing and that it has its act of existing from the First Being
which is existence only; and this is the First Cause, God.
Carl: Metaphysics 44
esse are really distinct must have its act of existence caused by some extrinsic efficient cause. One
must therefore arrive at some first cause of the existence of all other things, a being in which
essence and esse are identical, and St. Thomas remarks that this First Being and First Cause is
God.
does hold that a thing’s substantial form is a cause of its esse—but a formal cause rather than an efficient
cause.
Carl: Metaphysics 45
6.4. Other Ways of Arguing for Essence-Esse Composition
Besides the forms of argument that we have identified in the two stages of c. 4 of the De
ente et essentia (the intellectus essentiae argument and the argument from the impossibility of
there being more than one being whose essence is its very esse), St. Thomas offers a number of
other arguments in favor of essence-esse composition in finite substances. We will consider at least
one textual example for each of the three other varieties of argument identified by Msgr. Wippel.
The “genus” argument48
As Msgr. Wippel explains, St. Thomas frequently claims and argues that whatever belongs
to a genus must be composed of essence or quiddity and esse. Most often, this sort of claim
appears in the context of argumentation supporting the thesis that God is not in any genus. For
example, in ST 1.3.5, St. Thomas argues as follows:
Tertio, quia omnia quae sunt in genere uno,
communicant in quidditate vel essentia generis,
quod praedicatur de eis in eo quod quid est.
Differunt autem secundum esse: non enim idem est
esse hominis et equi, nec huius hominis et illius
hominis. Et sic oportet quod quaecumque sunt in
genere, different in eis esse et quod quid est, idest
essentia. In Deo autem non differt, ut ostensum est.
Unde manifestum est quod Deus non est in genere
sicut species.
Third, since all those that are in one genus share in
the quiddity or essence of the genus, which is
predicated of them as what-it-is. But they differ
with regard to being (esse): for the being (esse) of
a man is not the same as [that] of a horse, nor [the
being] of this man and of that man. And thus it
must be that whatever [things] are in a genus, in
them being (esse) and what-it-is (quod quid est),
that is essence. But in God it does not differ, as
was shown. Wherefore it is manifest that God is
not in a genus as a species.
Being—in the sense of existence or the act of being—is not the same in man or in horse,
nor in this man and in that man. If one needs an argument for this claim, one need only consider
that a man can continue to exist even if a horse or another man should cease to exist: and what is
separable in this way is not the same.49 But the many men and the many horses do share in the
quiddity or essence of the genus animal (just as they each also share in their respective species).
Therefore, esse and essence must differ in them.
It might be questioned whether this formulation of the argument establishes a real
distinction between esse and essence, since it depends upon the essence of the genus in which
members of a given genus share—and the distinction of the genus itself from the individual is a
logical distinction rather than a real distinction.50
48Wippel 157-61.
49Whereas we want to emphasize that real distinction (or composition) does not imply separability (i.e., the
possible existence of one item without the other), nevertheless separability always implies real
distinction. In this case, that a man can exist independently of a horse serves to indicate that the existence
or act of being of the man is not the same as the existence or act of being of the horse.
50See Wippel 161, in which Msgr. Wippel gives his evaluation of the “genus” argument, judging that as this
argument is formulated by St. Thomas, it is not sufficient to establish a real composition or distinction of
esse and essence; rather, it needs support from other metaphysical theses against objections. My purpose
in these next few paragraphs is to indicate some possible ways of supporting the “genus” argument
Carl: Metaphysics 46
To this objection, it can be replied that although the genus animal itself does not exist
outside the mind, and although animal is only logically distinct from Alexander or Bucephalus,
nevertheless Alexander and Bucephalus are generically identical in reality. The logical distinction
of the genus animal has its foundation in what this individual animal and that individual animal
really share in common. So, when it is argued that the essence of animal is the same in Alexander
and Bucephalus, this is not to be understood as a claim about sameness that is merely logical,
intentional, and posterior to the activity of the mind. Therefore, that Alexander and Bucephalus
really share in the essence of animal (or that Aristotle and Alexander really share in the species
man), but differ in their existences or acts of being, seems sufficient to establish the real distinction
of these principles in these individuals.
Yet, it might still be objected that this formulation of the “genus” argument does not
concern the individual essence—that is, the essence of this individual—but only concerns essence
taken as a universal, as what is common to many. Even if Alexander and Bucephalus are
generically the same (or Alexander and Aristotle are specifically the same), still they differ
numerically: and perhaps existence or the act of being (esse) is part of the individual essence of
each of these individuals, without it being the case that esse really differs from or is composed with
the individual essence.
To answer this objection, we need to make reference to two theses that we will articulate in
full and defend later. The first concerns the principle of individuation—that is, the principle that
serves to diversify a species into its many individuals. As we shall later see, St. Thomas holds that
the principle of individuation is designate matter. According to this thesis, Socrates differs from
Plato, because Socrates has this flesh and these bones, whereas Plato has that flesh and those
bones. Flesh and bones, taken universally, belong to the essence of man taken universally; but the
individual essence of Socrates includes his designate matter, as distinguished from matter in the
abstract. The second thesis concerns the character of form as a principle: according to St. Thomas,
a thing’s form gives it its esse, because the formal cause is by definition that which makes a thing
to be (esse) what it is.
Now, according to the first of these theses, the essence of man taken as a universal is
contracted to the individual by designate matter, which is a principle of potency relative to the
human form. According to the second thesis, it is by virtue of a thing’s form that it exists or has
esse. To conclude that esse is a part of the individual essence would therefore suggest that esse (or
the act of being) is the designate matter of a thing; but it is form and not matter that gives esse, and
so it cannot be the case that esse is a part of the individual essence. Therefore, the individual
essence and esse must differ really.
That St. Thomas understands the “genus” argument to establish a real distinction and
composition of essence and esse is clear from a second text in which he employs this form of
argumentation, DV 27.1 ad 8. In this context, St. Thomas employs a form of the “genus” argument
in a different context, in order to argue that grace can be something created and accidental, despite
the fact that grace is a simple form. Although this text’s purpose is explicitly theological, the
presentation of the “genus” argument is itself philosophical in character. In this text, St. Thomas
writes:
Ad octavum dicendum, quod omne quod est in
genere substantiae, est compositum reali
To the eighth it is said that whatever is in the genus
of substance is composed by a real composition;
against objection.
Carl: Metaphysics 47
compositione; eo quod id quod est in
praedicamento substantiae est in suo esse
subsistens, et oportet quod esse suum sit aliud
quam ipsum, alias non posset differre secundum
esse ab illis cum quibus convenit in ratione suae
quidditatis; quod requiritur in omnibus quae sunt
directe in praedicamento: et ideo omne quod est
directe in praedicamento substantiae, compositum
est saltem ex esse et quod est.
Sunt tamen quaedam in praedicamento substantiae
per reductionem, ut principia substantiae
subsistentis, in quibus praedicta compositio non
invenitur; non enim subsistunt, ideo proprium esse
non habent. Similiter accidentia, quia non
subsistunt, non est eorum proprie esse; sed
subiectum est aliquale secundum ea; unde proprie
dicuntur magis entis quam entia.
Et ideo, ad hoc quod aliquid sit in praedicamento
aliquo accidentis, non requiritur quod sit
compositum compositione reali, sed solummodo
compositione rationis ex genere et differentia: et
talis compositio in gratia invenitur.
because that which is in the predicament of
substance is subsisting in its act of being (esse),
and it must be that its act of being (esse) is other
than [the thing] itself; otherwise it could not differ
in the act of being (esse) from those [things] with
which it shares in the intelligibility (ratio) of its
quiddity, which is necessary in all those which are
directly in the predicament: and therefore whatever
is directly in the predicament of substance, is
composed at the least of the act of being (esse) and
what-is (quod est).
But there are some things in the predicament of
substance by reduction, such as the principles of a
subsistent substance, in which the aforementioned
composition is not found; for they do not subsist,
and therefore do not have their own act of being.
Similarly accidents, because they do not subsist, of
them there is not their own act of being; but the
subject is some way because of them; wherefore
they are more properly said [to be] “of a being”
rather than beings.
And therefore, for this that something be in some
predicate of accident, it is not required that it be
composite by a real composition, but only by a
composition of reason from genus and difference:
and such a composition is found in grace.
St. Thomas begins with a version of the “genus” argument that avoids some of the
difficulty suggested by the formulation found in ST 1.3.5: in this text from the De veritate, he
offers his argument in terms of what belongs to the category of substance and therefore shares in
the ratio of the quiddity of substance. He explicitly states that the composition of what-is and esse
in all members of the category of substance is a real composition, and this is distinguished in the
third paragraph from a composition of reason by genus and difference.
Once again, the “genus” argument itself proceeds from the sameness in essence but
difference in esse among members of a genus, but in this case the argument is restricted to the
genus of substance. Because a given substance is the same as another substance insofar as both
share in the intelligible content of the quiddity of substance, but one substance differs in its esse
Carl: Metaphysics 48
from another substance, it must be that in each substance there is a composition of quiddity and
esse—or as St. Thomas expresses it here, of what-is (being in the sense of ens) and esse.
In the second paragraph of this text, St. Thomas adds some helpful points of clarification.
By the principles of a substance, St. Thomas means its form and its matter (at least for those
substances that are composed of form and matter): this substance’s substantial form and prime
matter belong to the category of substance by reduction, but form and matter are not themselves
composed of essence and esse. As we will explain later, in our discussion of form-matter
composition, for St. Thomas the essence of a corporeal substance includes both form and matter,
whereas the essence of a separate substance is form alone. Furthermore, accidents do not admit of
the same composition of essence and esse, because they exist insofar as they modify substance,
rather than subsisting independently.
Arguments based on participation51
We have already seen one example of an argument in which St. Thomas proceeds from the
participation of ens in esse to a claim about the real composition of ens, in Exp. De ebd. lec. 2, a
text that we can consider anew:
Deinde cum dicit: Omni composito etc., ponit
conceptiones de composito et simplici, quae
pertinent ad rationem unius, et est considerandum
quod ea quae supra dicta sunt de diversitate ipsius
esse et eius quod est, est secundum ipsas
intentiones. Hic ostendit quomodo applicetur ad
res; et primo ostendit hoc in compositis, secundo
in simplicibus, ibi: Omne simplex etc.
Est ergo primo considerandum quod sicut esse et
quod est differunt secundum intentiones, ita in
compositis differunt realiter. Quod quidem
manifestum est ex praemissis. Dictum est enim
supra quod ipsum esse neque participat aliquid ut
eius ratio constituatur ex multis, neque habet
aliquid extrinsecum admixtum ut sit in eo
compositio accidentalis; et ideo ipsum esse non est
compositum; res ergo composita non est suum
esse; et ideo dicit quod in omni composito aliud est
esse ens et aliud ipsum compositum quod est
Then when he says: In every composite etc., he
posits conceptions about the composite and the
simple, which pertain to the character of unity, and
it must be considered that those things said above
about the diversity of being (esse) itself and of
what-is (quod est), is according to the intentions
themselves. Here he shows how [this] is applied to
things; and first he shows this about composites,
second about simples, where [he says]: Every
simple etc.
Therefore first it must be considered that just as
being (esse) and what is (quod est) differ according
to intention, so also in composite [things] they
differ really. Indeed this is manifest from what
preceded. For it was said above that being (esse)
itself neither participates anything as though its
ratio were constituted from many, nor does it have
something extrinsic admixed with it as though
there were in it accidental composition; and
therefore being (esse) itself is not composite;
therefore a composite thing is not its esse; and
51Wippel 161-70.
Carl: Metaphysics 49
participando ipsum esse. therefore he says that in every composite it is one
thing to be a being (esse ens) and another to be the
composite itself, which is, by participating ipsum
esse.
This argument is restricted to composite things (that is, to composites of matter and form).
St. Thomas argues that being (esse) itself is not composite in any way, and so there must be a lack
of real identity between the composite being (ens) and its existence or act of being (esse). Having
given this argument, St. Thomas proceeds to consider an argument that will also pertain to simple
substances (i.e., to angels):
Deinde cum dicit: Omne simplex etc., ostendit
qualiter se habeat in simplicibus in quibus necesse
est quod ipsum esse et id quod est sit unum et idem
realiter. Si enim esset aliud realiter id quod est et
ipsum esse, iam non esset simplex sed
compositum. Est tamen considerandum quod, cum
simplex dicatur aliquid ex eo quod caret
compositione, nihil prohibet aliquid esse secundum
quid simplex, in quantum caret aliqua
compositione, quod tamen non est omnino
simplex; unde et ignis et aqua dicuntur simplicia
corpora, in quantum carent compositione quae est
ex contrariis quae invenitur in mixtis, quorum
tamen unumquodque est compositum, tum ex
partibus quantitativis, tum etiam ex forma et
materia. Si ergo inveniantur aliquae formae non in
materia, unaqueque earum est quidem simplex
quantum ad hoc quod caret materia, et per
consequens quantitate quae est dispositio materiae.
Quia tamen quaelibet forma est determinativa
ipsius esse, nulla earum est ipsum esse, sed est
habens esse; puta secundum opinionem Platonis,
ponamus formam immaterialem subsistere quae sit
idea et ratio hominum materialium, et aliam
formam quae sit idea et ratio equorum, manifestum
erit quod ipsa forma immaterialis subsistens, cum
Then when he says: Every simple etc., he shows
how it is in simple [things] in which it is necessary
that being itself and that-which-is be one and the
same really. For if that-which-is and being (esse)
itself were other, then it would not be simple but
composite. Nevertheless it must be considered that,
since something is called simple from this that it
lacks composition, nothing prohibits something
from being simple in a qualified way (secundum
quid), insofar as it lacks some composition, which
is nevertheless simple in every way; whence both
fire and water are called simple bodies, insofar as
they lack the composition from contraries which is
found in mixed [bodies]; nevertheless each of these
[(fire and water)] is composite, both from
quantitative parts and also from form and matter. If
therefore there be found some forms not in matter,
each of these is indeed simple insofar as it lacks
matter, and consequently quantity, which is a
disposition of matter. Nevertheless since each form
is determinative of being (esse) itself, none of
these is being (esse) itself, but is [something]
having being (habens esse); for instance according
to the opinion of Plato, should we posit as
subsisting an immaterial form which is the idea
and intelligibility of material men, and another
Carl: Metaphysics 50
sit quiddam determinatum ad speciem, non est
ipsum esse commune, sed participat illud. Et nihil
differt quantum ad hoc si ponamus alias formas
immateriales altioris gradus quam sint rationes
horum sensibilium ut Aristoteles voluit;
unaquaeque enim illarum, in quantum distinguitur
ab alia, quaedam specialis forma est participans
ipsum esse, et sic nulla earum erit vere simplex. Id
autem solum erit vere simplex quod non participat
esse, non quidem inherens sed subsistens. Hoc
autem non potest esse nisi unum, quia, si ipsum
esse nihil aliud habet admixtum praeter id quod est
esse, ut dictum est, impossibile est id quod est
ipsum esse multiplicari per aliquid diversificans,
et, quia nihil aliud praeter se habet adiunctum,
consequens est quod nullius accidentis sit
susceptivum. Hoc autem simplex, unum et sublime
est ipse Deus.
form which is the idea and intelligibility of horses,
it would be obvious that the subsisting immaterial
form itself, since it is determined to a species, is
not common being itself (ipsum esse commune),
but participates it. And nothing would change
about this if we should posit other immaterial
forms of a higher grade than the intelligibilities of
these sensible [things], as Aristotle wished; for
each of those, insofar as it is distinguished from the
others, is a certain special form participating being
(esse) itself, and thus none of these will be truly
simple. But that alone will be truly simple which
does not participate being (esse), indeed not
inhering but subsisting. But this cannot be but one,
if being (esse) itself has nothing else admixed
besides what-it-is-to-be, as was said, it is
impossible that what-it-is-to-be be multiplied
through something diversifying [it], and since
nothing else is adjoined to it, consequently it is
susceptible to no accidents. But this simple, one
and sublime, is God Himself.
In this argument, St. Thomas combines elements of what we above called the argument
from the impossibility of there being more than one thing in which essence and esse are identical
with the language of participation. He distinguishes between what is absolutely simple (omnino
simplex) and what is simple in a qualified or relative way (simplex secundum quid). As he proceeds
to explain, God alone is absolutely simple, whereas other things (including both angels and even
certain bodies, such as the elements) are called simple only in a qualified or relative way. If one
posits immaterial forms, whether these are Platonic Forms or Aristotelian separate substances,
these will be determined to species and will differ from one another, and as a consequence they
will be said to participate esse rather than to be identical with being itself. As we will later explain
in our discussion of form-matter composition, it pertains to the formal cause to determine and limit
esse, as St. Thomas notes here. As a consequence, even in a pure form without matter, essence or
form will be other than the esse that it determines and limits: it will not be esse itself.
Argument based on the limited character of individual beings52
A final category of argument for essence-esse composition is what Msgr. Wippel calls the
argument based on the limited character of individual beings. This form of argument appears
explicitly and independently in only one text: In Sent. 1.8.5.1. In this article, St. Thomas asks
whether any creature is simple. As we have seen in the previous text we considered, St. Thomas
distinguishes between what is simple in every way (omnino simplex) and what is simple in a
52Wippel 170-76.
Carl: Metaphysics 51
qualified way (simplex secundum quid). In In Sent. 1.8.5.1, St. Thomas is concerned with the
former, absolute kind of simplicity, and he argues that no creature is simple in this way.
Praeterea, omnis creatura habet esse finitum. Sed
esse non receptum in aliquo, non est finitum, immo
absolutum. Ergo omnis creatura habet esse
receptum in aliquo; et ita oportet quod habeat duo
ad minus, scilicet esse, et id quod esse recipit.
Furthermore, every creature has finite being (esse).
But being (esse) not received in something is not
finite, but absolute. Therefore every creature has
being (esse) received in something else; and so it is
necessary that it have at least two [components],
namely being (esse) and that which receives being
(esse).
This interesting argument depends upon two other claims: (1) a creature’s being is finite,
and (2) unreceived esse is absolutely unlimited. The former claim receives no special
argumentation in this text, and as Msgr. Wippel notes, it is a claim that St. Thomas is willing to
take for granted. The latter claim seems to be axiomatic for St. Thomas. As an axiom, it must
depend upon the notion of esse: So what is it about the notion of esse that implies that esse as such
is unlimited, or that it is not self-limiting?
We will conclude our treatment of essence-esse composition with reference to one of the
most famous texts of St. Thomas, in which he succinctly states what he understands as central to
the notion of esse or the act of being. This text is De potentia q. 7 a. 2 ad 9:
Ad nonum dicendum, quod hoc quod dico esse est
inter omnia perfectissimum: quod ex hoc patet
quia actus est semper perfectior potentia. Quaelibet
autem forma signata non intelligitur in actu nisi per
hoc quod esse ponitur. Nam humanitas vel igneitas
potest considerari ut in potentia materiae existens,
vel ut in virtute agentis, aut etiam ut in intellectu:
sed hoc quod habet esse, efficitur actu existens.
Unde patet quod hoc quod dico esse est actualitas
omnium actuum, et propter hoc est perfectio
omnium perfectionum. Nec intelligendum est,
quod ei quod dico esse, aliquid addatur quod sit eo
formalius, ipsum determinans, sicut actus
potentiam: esse enim quod huiusmodi est, est aliud
secundum essentiam ab eo cui additur
determinandum. Nihil autem potest addi ad esse
quod sit extraneum ab ipso, cum ab eo nihil sit
extraneum nisi non-ens, quod non potest esse nec
To the ninth it is said that this which I call esse is
the most perfect among all [perfections]: which
follows from this, that act is always more perfect
than potency. Now each designate form is not
understood in act except through this that it is
posited to be. For humanity or fieriness can be
considered as existing in potency in matter, or as in
the power of an agent, or even as [it is] in the
intellect: but what has esse is made an existent in
act. Whence it follows that this which I call esse is
the actuality of every act, and because of this it is
the perfection of every perfection. Nor should it be
understood that to what I call esse is anything more
formal than it added, determining it, as act [is more
formal than and determines] potency: for esse in
this sense is essentially other from that to which it
is added [so as] to be determined [by it]. Now
nothing can be added to esse which is extraneous
Carl: Metaphysics 52
forma nec materia. Unde non sic determinatur esse
per aliud sicut potentia per actum, sed magis sicut
actus per potentiam.
to it, since nothing is extraneous to it except nonbeing, which cannot be either form or matter.
Whence esse is not thus determined by another as
potency [is determined] by act, but rather as act [is
determined] by potency.
Esse is described here as the actuality of every act and the perfection of every
perfection. St. Thomas argues that this follows from the fact that a given designate form (that is,
the form of this thing) may exist potentially in matter, or virtually in the agent that can cause this
form, or even in the intellect: but the designate form is never understood in act unless it is
understood or supposed to be. That is, the actual intelligibility of form is itself dependent upon
existence or the act of being (esse): and because a principle of intelligibility is always a formal
principle or act principle, St. Thomas concludes that esse is more formal than the form or essence,
that it is the actuality of every act and the perfection of every perfection.
Another way of putting this same insight about esse is to note, as St. Thomas does in ST
1.4.2, that the perfection of being is the most fundamental perfection and contains every other
perfection:
Omnium autem perfectiones pertinent ad
perfectionem essendi: secundum hoc enim aliqua
perfecta sunt, quod aliquo modo esse habent.
But all perfections pertain to the perfection of
being (esse): for things are perfect insofar as they
have being (esse) in some mode.
The actuality of any perfection whatsoever is existence (esse), because a thing is perfect
insofar as it exists or has being (esse) in some way. It is in light of such a claim about being (esse)
that St. Thomas can justifiably treat the claim encountered above—that esse is only limited by
being received—as an axiom or immediate principle. Esse is the actuality of every act and the
perfection of every perfection; it is more formal than form or essence and is only limited by the
form or essence taken as a principle of potency. We will have more to say about this issue when we
make general comments about the various modes of act-potency composition found in finite
beings, later in our course.
Carl: Metaphysics 53
7. Substance-Accident Composition
Having completed our lengthy discussion of essence-esse composition in all of the beings
falling under the subject of metaphysics, ens commune, we now turn to the other mode of
composition that St. Thomas holds to be common to all such beings: this is the composition of
substance and accident. We will treat a selection of the topics treated by Msgr. Wippel concerning
substance-accident composition, beginning with some of the points of clarification to be offering
concerning the meaning of substance.
7.1. What is Substance?
We have previously treated St. Thomas’s appropriation of the Aristotelian claim that
substance is the primary referent of the term being (ens), whereas accidents are beings in only a
secondary and dependent way. For Aristotle this claim is expressed in terms of pros hen
equivocation, whereas for St. Thomas this is a matter of analogical predication—to be precise,
what we previously distinguished as the horizontal or predicamental analogy.
In the Aristotelian Metaphysics, the pros hen equivocal character of being leads Aristotle to
a focus on substance as the primary referent of being. The question, “what is substance?” becomes
one of the central questions of the Metaphysics, with Aristotle addressing this question in terms of
form and matter, act and potency, and a focus on the highest instances of substance (the separate
substances). Although because of the limitations of time, we cannot present this material from the
Metaphysics itself, it must be acknowledged that most of what St. Thomas contends concerning
substance is indebted to Aristotle’s Metaphysics.
We considered above, in our treatment of the meaning of ens commune, a text from the
Commentary on the Metaphysics, Book V, in which St. Thomas has commented on the division of
ens into accidental being and essential being and the further division of essential being into being
in the categories and being in the mind. We now turn to the content of the following lectio of St.
Thomas’s Commentary, lec. 10. We should recall that Book V of the Metaphysics presents a
lexicon of metaphysical terminology: the subject of c. 8, about which lec. 10 comments, is the
meaning of substance.
In this text, St. Thomas follows Aristotle in distinguishing four meanings of the term
substance:
(1) first substance / primary substance, as this is treated in the Categories:
Circa primum ponit quatuor modos; quorum
primus est secundum quod substantiae particulares
sunt substantiae, sicut simplicia corpora, ut terra et
ignis et aqua et huiusmodi. Et universaliter omnia
corpora, etiam si non sint simplicia, sicut mixta
similium partium, ut lapis, sanguis, caro et
huiusmodi. Et iterum animalia quae constant et
huiusmodi corporibus sensibilibus, et partes
eorum, ut manus et pedes et huiusmodi. . . . Haec
Concerning the first, he posits four modes; of these
the first is [that] according to which particular
substances are substances, as the simple bodies,
such as earth and fire and water and others of this
kind. And universally all bodies, even if they are
not simple, such as mixed [bodies] of
homogeneous parts, such as stone, blood, flesh,
and others of this kind. And again animals which
are composed from sensible bodies of this kind,
Carl: Metaphysics 54
enim omnia praedicta dicuntur substantia, quia non
dicuntur de alio subiecto, sed alia dicuntur de his.
Et haec est descriptio primae substantiae in
praedicamentis.
and [animal’s] parts. . . . For all these mentioned
are called substance, because they are not said of
another subject, but others are said of these. And
this is the description of first substance in the
Categories.
In this text, St. Thomas provides a number of examples of primary substances, following
Aristotle’s text:
(a) the simple bodies
(b) homogeneous mixed bodies
(c) animals and their parts
[(d) the daemonia, mentioned by Aristotle in his text and briefly commented upon by St.
Thomas)]
These are called substance in the sense of first substance from Aristotle’s Categories, that
which is neither said of nor said to be in another, but rather that about which such things are said.
Concerning the second point, that in general homogeneous mixed bodies are substances, we have
noted previously in our course that for St. Thomas in this way things such as bread and wine are
substances, even though they only come to be by art.
(2) The intrinsic formal cause of the being of a first substance:
Dicit quod alio modo dicitur substantia quae est
causa essendi praedictis substantiis quae non
dicuntur de subiecto; non quidem extrinseca sicut
efficiens, sed intrinseca eis, ut forma. Sicut dicitur
anima substantia animalis.
He says that in another way [that] is called
substance which is the cause of being (causa
essendi) of the aforementioned substances which
are not said of a subject; and not extrinsic as an
efficient cause, but intrinsic to them, as a form.
Thus the soul is called the substance of an animal.
Aristotle contends that one may refer to the intrinsic formal cause—such as the soul of an
animal—as the substance of the thing. We will see what both he and St. Thomas do with this claim
shortly.
(3) The parts of substances that limit them and render them divisible:
We need not dwell on this division of substance, which is suggested by both Plato and
Pythagoras, for Aristotle and St. Thomas suggest it and proceed to dismiss it. In brief, the
suggestion is that the surface and lines of a thing are its substance, because the thing is destroyed
when its surfaces and lines are destroyed. Even though St. Thomas discusses this as a true meaning
of the term substance (because it confuses some of the properties of a body with the substance
itself), nevertheless it suggests that the term substance can be taken as referring to what is in some
way essential to a thing; and this suggests to us the fourth meaning of substance, as essence.
(4) The quiddity or essence of a thing:
Dicit quod etiam quidditas rei, quam significat He says also that the quiddity of a thing, which the
Carl: Metaphysics 55
definitio, dicitur substantia uniuscuiusque. Haec
autem quidditas sive rei essentia, cuius definitio est
ratio, differt a forma quam dixit esse substantiam
in secundo modo, sicut differt humanitas ab anima.
Nam forma est pars essentiae vel quidditas rei.
Ipsa autem quidditas vel essentia rei includit omnia
essentialia principia. Et ideo genus et species
dicuntur esse substantia eorum, de quibus
praedicantur, hoc ultimo modo. Nam genus et
species non significant tantum formam, sed totam
rei essentiam.
definition signifies, is called the substance of each
thing. But this quiddity or essence of a thing, of
which the definition is the intelligible content
(ratio), differs from the form which he said to be
substance in the second mode, as humanity differs
from the soul. For the form is part of the essence or
quiddity of the thing. But the quiddity or essence
itself of a thing includes all [its] essential
principles. And therefore the genus and species are
said to be the substance of those of which they are
predicated, in this last way. For the genus and
species do not signify form alone, but the whole
essence of a thing.
The example given of an essence—humanity—differs from the intrinsic form (such as the
soul) in that the essence includes the form but also includes the thing’s other essential principles.
Principally, St. Thomas has in mind matter. As we have said before, knowledge of the essence of
any corporeal substance includes a knowledge of both form and matter, albeit matter taken in the
abstract. In the second way, substance meant the intrinsic formal cause of the thing; in this fourth
way, substance is the essence or quiddity. It is also in this way that genus or species are said to be
the substance of a thing, because they signify not form alone, but the entire essence of a thing.
In his Commentary (and following Aristotle), St. Thomas reduces these four meanings of
substance to two. As already indicated, the third mode of substance is dismissed, leaving only
three; and St. Thomas combines the second and fourth modes, because the latter mode (essence)
includes the former (the intrinsic form). This leaves the following two modes:
(1) Substance as subject; primary substance; the suppositum or hypostasis53
(2) Substance as essence, quiddity, form54 or nature
Whenever one encounters the term substance in Aristotelian-Thomistic philosophy, one
must ask whether the term substance refers to the suppositum or to the essence.
Now, in the Categories, Aristotle draws a twofold distinction concerning substance into
primary substance and secondary substance, and at this point we must ask: is this division from the
Categories the same as the division of substance into suppositum and essence? The text from In
Meta. 5.10 might suggest that we should identify secondary substance with essence, insofar as it
said that it is in the fourth mode distinguished there that genus and species are called substance.
53See Wippel 203-204 for parallel texts in which St. Thomas draws the twofold division of meanings of
substance and refers to primary substance as suppositum and hypostasis.
54We mean by form here still the entire essence, rather than just the formal cause as distinguished from the
matter of the thing. As St. Thomas will put it elsewhere, essence is called form as the forma totius, to be
distinguished from the forma partis that is the substantial form.
Carl: Metaphysics 56
However, as Msgr. Wippel details (pp. 205-208), one should not identify the secondary
substance of the Categories with substance as essence or quiddity. As St. Thomas argues in De pot.
9.1, whereas the genus or species is predicated of a primary substance (in the language of the
categories, secondary substance is what is said of a primary substance), the essence cannot be
predicated of the individual. That is, while it is correct to say that Socrates is animal or man (his
genus and his species), it cannot be said that Socrates is humanity. This is the case because the
essence or nature is a formal part of the suppositum rather than being identical with the
suppositum, at least in the case of matter-form composites. We will have more occasion to discuss
this issue when we take up matter-form composition and the principle of individuation.
7.2. Derivation of the Ten Categories
One distinguishes substance from accident insofar as one distinguishes substance as the
primary mode of being from the other nine modes of being, the nine accidental modes. It is fitting
to consider at this time St. Thomas’s systematic exposition (or as Msgr. Wippel calls it, his
derivation) of the ten categories as modes of being.
A predicate can be related to a subject (with respect to what the predicate expresses) in
three ways:
1) the predicate is really identical with that which serves as the subject; for example,
“Socrates is animal.” “Here Socrates is that very thing which is an animal,” and animal
signifies the subject Socrates himself and what Socrates is, rather than anything accidental
about Socrates. This is the category of SUBSTANCE (1).
2) the predicate can be taken from something which is in the subject (this is how we have
broadly defined the accidents so far); but this in one of two ways:
a) the predicate can name something in the subject considered absolutely
i) but following upon the matter of the subject, in which case we have the
category of QUANTITY (2).
ii) but following upon the form of the subject, in which case we have the
category of QUALITY (3).
b) the predicate can be taken from something which is in the subject only
considered with reference to something else; this is the category of RELATION
(4).
3) the predicate can be derived from something extrinsic to the subject, and this in two
ways:
a) the predicate can be taken from something totally extrinsic to the subject
i) and if that from which the predicate is derived is not a measure of the
subject, then we have the category of HABIT (5).
ii) but if this predicate is taken from a measure of the subject, then we
have:
1) the category of TIME (or WHEN) (6), which is taken from the
extrinsic measure of time
2) the category of PLACE (or WHERE) (7), which is taken from
the extrinsic measure of place, without consideration of the
orientation of the parts of the subject
3) the category of POSITION (8), which is taken from the the
extrinsic measure of place, with consideration of the orientation of
the parts of the subject
Carl: Metaphysics 57
b) the predicate can be taken from something that is both outside the subject and
from a certain point of view also in the subject of which it is predicated:
i) and if the subject is the principle of what is extrinsic, then it is
predicated in the category of ACTION (9)
ii) and if the subject is the terminus of what is extrinsic, then it is
predicated in the category of PASSION (10).55
St. Thomas’s systematic treatment of the ten categories according to ten modes of
predication depends upon the more fundamental claim that these various modes of predication
depend upon diverse modes of being in things. In the text introducing the derivation of the
categories just treated, St. Thomas writes:
Dicit ergo primo, quod illa dicuntur esse secundum
se, quaecumque significant figuras praedicationis.
Sciendum est enim quod ens non potest hoc modo
contrahi ad aliquid determinatum, sicut genus
contrahitur ad species per differentias. Nam
differentia, cum non participet genus, est extra
essentiam generis. Nihil autem posset esse extra
essentiam entis, quod per additionem ad ens
aliquam speciem entis constituat: nam quod est
extra ens, nihil est, et differentia esse non potest.
Unde in tertio huius probavit Philosophus, quod
ens, genus esse non potest.
Unde oportet, quod ens contrahatur ad diversa
genera secundum diversum modum praedicandi,
qui consequitur diversum modum essendi; quia
“quoties ens dicitur,” idest quot modis aliquid
praedicatur, “toties esse significatur,” idest tot
modis significatur aliquid esse. Et propter hoc ea
in quae dividitur ens primo, dicuntur esse
praedicamenta, quia distinguuntur secundum
diversum modum praedicandi. Quia igitur eorum
quae praedicantur, quaedam significant quid, idest
substantiam, quaedam quale, quaedam quantum, et
sic de aliis; oportet quod unicuique modo
praedicandi, esse significet idem; ut cum dicitur
He says first therefore that those are said to be
essentially which signify the figures of predication.
For it must be known that being cannot be
contracted to something determinate in the way
that a genus is contracted to species through
differences. For a difference, since it does not
participate the genus, is outside the essence of the
genus. But nothing can be outside the essence of
being [such] that through addition to being it
constitutes a species of being: for what is outside
being is nothing and cannot be a difference.
Wherefore in the third [book of] this [work] the
Philosopher proved that being cannot be a genus.
Whence it is necessary that being is contracted to
diverse genera according to a diverse mode of
predicating, which follow a diverse mode of being;
since “being is said as many ways,” that is
something is predicated in as many modes, “as to
be is signified,” that is as many ways as something
is signified to be. And because of this those
[things] into which being is first divided are said to
be predicaments, since they are distinguished
according to diverse modes of predicating. Since
therefore of those [things] which are predicated,
some signify what, that is substance, some how,
55These remarks are based on In Meta. 5.9 and Wippel 213-15.
Carl: Metaphysics 58
homo est animal, esse significat substantiam. Cum
autem dicitur, homo est albus, significat
qualitatem, et sic de aliis.
some how much, and thus for the others; it is
necessary that for each mode of predicating, to be
signifies the same [i.e., a mode of being]; as when
it is said man is animal, to be signifies substance.
But when it is said, man is white, [to be] signifies
quality, and likewise for the others.
Being must be contracted to the categories according to diverse modes of predicating
because it cannot be so contracted according to some difference added to being taken as a genus.
Being must be contracted in some other way, and here St. Thomas claims that being is contracted
to its modes in a manner that parallels the various possible modes of predicating. I think the
appropriate background for this claim is the distinction between apprehension and judgment and
St. Thomas’s claim, which we examined early in the course, that being is not known simply
through the act of apprehension: we said that knowledge of being depends upon the second
operation of the mind, which is judgment. One’s apprehensive grasp of being is complex, being
expressed by a formula like “what has existence” or “that which is.”
To put it another way, being is not known as a genus is known, through abstraction from its
species. To the degree that there is an apprehensive grasp of being, this grasp depends upon
judgment. Therefore it should be no surprise that being is contracted to its ten modes, not by
differences, but according to ten different modes of predicating—that is, ten different modes of
judgment. Just as the signification of the term being depends upon what is grasped by judgment
(being is “that which is,”) so too does the signification of each of the ten categories, taken as ten
modes of being, depend upon the modes according to which one can predicate something. Hence,
substance signifies a mode of being according to the meaning of the verb “to be” in a predication
expressing what something is; whereas quality signifies a mode of being according to the meaning
of the verb “to be” in a predication expressing how something is, etc.
7.3. Other Points Concerning Substance and Accident
Due to the constraints of time, we can only briefly summarize a number of other points to
be made concerning substance and accident and the relationship between them.
The definitions of substance and accident
As Msgr. Wippel notes (pp. 228-237), on a number of occasions St. Thomas stresses that
“being in itself (per se)” is not the definition of substance. When he does comment in a positive
way about the definition of substance, St. Thomas offers the following: “the definition or quasidefinition of substance is a thing having quiddity, to which it is given or belongs to exist not in
something else.”56 The negative character of this definition should be noted, as well as the
inclusion of the reference to having quiddity and St. Thomas’s careful avoidance of defining
substance as something differentiated from being taken as a genus.
As for the definition of accident, in a similar manner St. Thomas qualifies that “being in a
subject” is not the definition of accident; rather, accident is “a thing to which it belongs to be in
56In Sent. 4.12.1.1 ql. 1 ad 2 [Moos 499]: “Sed definitio vel quasi definitio substantiae est res habens
quidditatem, cui acquiritur esse vel debetur non in alio.” The translation is from Wippel 231.
Carl: Metaphysics 59
something else.”57 Consequently St. Thomas frequently characterizes the mode of being
appropriate to accident as “being in” (inesse).58
Accidents and accidental being (esse)
Two related questions have long been discussed among the Thomistic commentators
concerning accidents and being (esse): (1) Does St. Thomas recognize a distinction between a
substance’s act of being (esse) and the acts of being of accidents? (2) Is there a real distinction
between or composition of an accidental form and accidental esse?
Concerning the first, although there have been dissenting voices among the Thomistic
commentators, the majority view and the view clearly supported by the texts of St. Thomas is that
there is a distinction between a substance’s act of being (that is, the act of being that actualizes its
essence) and the act of being (esse) of an accident. St. Thomas characterizes the being caused by
an accident as “a certain secondary being,” which we should understand as a further actualization
of the substance beyond its actuality according to its essence and substantial act of being.
However, whether one should posit a real distinction between an accidental form and the
accidental esse that modifies the subject of the accident is a more difficult question. As Msgr.
Wippel details, at least at some point earlier in his career, St. Thomas does seem to recognize such
a distinction. However, this distinction disappears from his later writings, and as we have seen
above in the so-called “genus” argument for essence-esse composition, St. Thomas argued that
whereas the composition of form and esse in the genus of substance is a real composition, by
contrast the distinction between an accidental form and its esse is only a logical distinction.59
The causal relationship between substance and accident
In general, St. Thomas characterizes the causal relationship between substance and
accident as a case of subject (or quasi-material) causality on the part of substance, and formal
causality on the part of accident. That is, an accident is a form that exists in a substance insofar as
it is a further actualization of the substance in some definite way: for example, Socrates’ being here
or Socrates’ being wise.
However, the class of accidents typically called properties (or proper accidents) must also
be characterized as caused by or flowing from the substance according to its essence. We will
quickly examine one text that draws the relevant distinctions in this regard, Quaestiones disputatae
De anima, q. 12, ad 7:
Ad septimum dicendum quod tria sunt genera
accidentium: quedam enim causantur ex
principiis speciei et dicuntur propria, sicut
risibile homini; quedam causantur ex
principiis indiuidui, et hoc dupliciter: quia uel
To the seventh objection [it is said] that there are
three kinds of accidents: for some are caused by
the principles of the species and are called proper
[accidents], such as risible of man; others are
caused by the principle of the individual, and this
in two ways: since they either have a permanent
57Ibid.: “Et similiter esse in subiecto non est definitio accidentis, sed e contrario res cui debetur esse in alio.”
The translation is from Wippel 234.
58Wippel 235.
59See Wippel 265 for summary comments about this issue.
Carl: Metaphysics 60
habent causam permanentem in subiecto, et
hec sunt accidentia inseparabilia, sicut
masculinum et femininum et alia huiusmodi;
quedam uero habent causam non semper
permanentem in subiecto, et hec sunt
accidentia separabilia, ut sedere et ambulare.
Est autem commune omni accidenti quod non
sit de essentia rei; et ita non cadit in
diffinitione rei. Vnde de re intelligimus quid
est absque hoc quod intelligamus aliquid
accidentium eius. Set species non potest
intelligi esse sine accidentibus que
consequuntur principium speciei; potest tamen
intelligi esse sine accidentibus indiuidui, etiam
inseparabilibus. Sine separabilibus uero
esse potest non solum species, set etiam
indiuiduum.
cause in the subject, and these are inseparable
accidents, such as masculine and feminine and
others of this kind; but others have a cause not
permanent in the subject, and these are separable
accidents, such as to see and to walk. But it is
common to every accident that it not be of the
essence of the thing; and thus it does not fall under
the definition of the thing. Wherefore we
understand of a thing what it is without this, that
we should understand something of its accidents.
But a species cannot be understood to exist without
the accidents which follow upon the principle of
the species; nevertheless it can be understood to
exist without the accidents of an individual, even
the inseparable [accidents]. But not only the
species, but even the individual, can exist without
the separable [accidents].
Here St. Thomas distinguishes among three kinds of accidents:
(1) Properties or proper accidents: these accidents follow from the essential character of
the species. For example, risibility follows upon rationality in man. While the substance, man, is
the subject of risibility, it must also be said that the essence of the substance is the formal cause of
risibility. This sort of causal relationship between the essence of a substance and its properties is at
issue in demonstration propter quid.
(2) Inseparable accidents: there are some accidental features of a thing that follow upon
some intrinsic cause that exists permanently, i.e., as long as the substance exists. For example, that
a human being is male or female is an inseparable accident. It does not belong to the species as a
property for a human being to be either male or female; instead it follows from what St. Thomas
here calls the principle of the individual, i.e., the substance’s material cause. Thus, while the
substance is the subject of an inseparable accident, one can also recognize the substance’s matter as
a cause of an inseparable accident.
(3) Separable accidents: these are accidents as we most commonly speak about them, the
changeable features of a given substance. That one is here now, there at another time; that one is
seeing now, but not at another time, etc. Typically when we speak of substance-accident
composition, we are speaking of separable accidents; and separable accidents are forms that further
actualize a given substance in a particular way.
Now, St. Thomas notes that it is common to every kind of accident that an accident does
Carl: Metaphysics 61
not belong to the essence (or consequently to the definition) of the thing.60 However, this does not
mean that a substance can exist without any of these kinds of accidents. St. Thomas clarifies that it
is impossible to conceive of the existence of a given species without its possessing the properties
or proper accidents that follow upon the essence of the species. Even though these properties do
not belong to one’s knowledge of what the species is, nevertheless one cannot think of the species
as existing without its properties.
By contrast, one can think of a species as existing without the other accidents, both
inseparable and separable. St. Thomas does not mean that one can conceive of an individual
without inseparable accidents; rather, he means that the species can exist without the inseparable
accidents, because it is possible for the species to be instantiated in an individual without a given
inseparable accident. However, the individual cannot exist without its inseparable accidents.
Finally, St. Thomas notes that both the species and the individual can exist without the
separable accidents: this follows from their being separable.
60It is in this sense that he will also say, in other contexts, that a thing’s act of being (esse) is accidental to
it—even though, strictly speaking, esse cannot be construed as an accident, because accidents actualize
substances beyond their substantial acts of being.
Carl: Metaphysics 62
8. Matter-form Composition in Corporeal Substances
Having considered the ways in which all beings other than God are composite—that is, by
the composition of essence and esse and the composition of substance and accidentwe now shift
our attention to a consideration of corporeal substances and another mode of composition in them:
the matter-form composition of their essences. We will consider the following questions: (1) How
does one establish the matter-form composition of corporeal substances? (2) What is prime matter,
and what can we say about it? (3) Can there be more than one substantial form in a thing? (4) What
is the principle of individuation in corporeal substances?61
8.1. Establishing the Hylomorphic Composition of Corporeal Substances
Following Aristotle, St. Thomas offers as the primary evidence of the matter-form
composition of corporeal substances the fact of motion or change. It is evident to the senses that
change occurs, i.e., that certain things come to be and pass away. However, change is only
intelligible when one admits the following three principles: (1) the form or characteristic that
comes to exist, (2) the privation of this form prior to the change, and (3) some subject of the
change that underlies both the privation and the form.62 These are Aristotle’s three principles of
nature: form, privation, and matter. All that is meant by the term matter in this broad sense is the
subject of a change, or that to which a change occurs.
The matter-form composition of corporeal substances is in this way first established
insofar as they are subject to change, and for this reason Msgr. Wippel characterizes this way of
establishing matter-form composition as more proper to physics than to metaphysics.63 Utilizing
this approach, one draws a distinction between two different kinds of change: (1) accidental
change, and (2) substantial change. The former kind of change involves the gain or loss of an
accidental form, without the substance that is the subject of the accident ceasing to exist. In the
latter kind of change, it is a substance that passes away, with another substance coming to be in its
place.
Understanding the term matter to mean just the subject of change, it is clear that the matter
of accidental change and the matter of substantial change will be different from one another. The
subject of an accidental change is just a substance, which is the subject of accidents. But the matter
of a substantial change cannot itself be a substance, because in a substantial change the substance
passes away and a new substance comes to exist in its place. For this reason, the matter that
underlies substantial change is not a substance, but what Aristotle and St. Thomas call prime
matter.
In the Commentary on the Physics, Book I, lec. 13, which concerns Aristotle’s presentation
of the three principles of nature, St. Thomas comments as follows:
Et dicit quod natura quae primo subiicitur And he says that the nature which is first subjected
61The presentation of these four topics closely tracks the organization of c. 9 of Msgr. Wippel’s The
Metaphysical Thought of Thomas Aquinas.
62See Physics 1.7.
63This should not present any special difficulty, as it will still pertain to metaphysics to clarify the
relationship between substantial form and prime matter, as principles, to the other principles of
composition distinguished in metaphysics. As we shall see, St. Thomas also characterizes the argument
for prime matter’s being a principle of pure potency distinct from all forms as pertaining to metaphysics
rather than physics.
Carl: Metaphysics 63
mutationi, idest materia prima, non potest sciri per
seipsam, cum omne quod cognoscitur, cognoscatur
per suam formam; materia autem prima
consideratur subiecta omni formae. Sed
scitur secundum analogiam, idest secundum
proportionem. Sic enim cognoscimus quod lignum
est aliquid praeter formam scamni et lecti, quia
quandoque est sub una forma, quandoque sub alia.
Cum igitur videamus hoc quod est aer quandoque
fieri aquam, oportet dicere quod aliquid existens
sub forma aeris, quandoque sit sub forma aquae: et
sic illud est aliquid praeter formam aquae et
praeter formam aeris, sicut lignum est aliquid
praeter formam scamni et praeter formam lecti.
Quod igitur sic se habet ad ipsas substantias
naturales, sicut se habet aes ad statuam et lignum
ad lectum, et quodlibet materiale et informe ad
formam, hoc dicimus esse materiam primam. Hoc
igitur est unum principium naturae: quod non sic
unum est sicut hoc aliquid, hoc est sicut aliquod
individuum demonstratum, ita quod habeat
formam et unitatem in actu; sed dicitur ens et
unum inquantum est in potentia ad formam.
to change, which is prime matter, cannot be known
in itself, since everything that is known, is known
through its form; but prime matter is considered [to
be] the subject of every form. But it is known
according to analogy, that is, according to
proportion. For thus we know that wood is
something other than the form of a bench and of a
bed, since at one time it is under the one form, at
another time under the other. When therefore we
see this which is air sometimes to become water, it
is necessary to say that something existing under
the form of air, at another time be under the form
of water: and so that is something besides the form
of water and besides the form of air, as the wood is
something besides the form of a bench and the
form of a bed. Therefore this [matter] is related to
the natural substances just as bronze is related to
the statue and wood to the bed, and everything
material and unformed to form; this we say to be
prime matter. Therefore this is one principle of
nature: which is not one as a this-something, that is
as some determinate individual, as though it had
form and unity in act; but it is called a being and
one insofar as it is in potency to form.
Following Aristotle, St. Thomas argues for prime matter by an analogy of
proportion(ality):
WOOD : BENCH & BED : : PRIME MATTER : AIR & WATER
This argument for recognizing prime matter is therefore based upon the recognition of a
kind of change that is not merely accidental, but is a change in the very kind of substance. Prime
matter is to be recognized not as a “this-something” (that is, as a concrete being or a supposit), but
rather as a principle of potency relative to the form of a substance. Prime matter is never known in
itself, and as we will clarify in a moment, it never exists independently of substance: it is just that
which underlies substantial change and therefore functions as the subject of substantial form.
In the Commentary on the Metaphysics, Book VII, lec. 2 (#1285 – 1289), St. Thomas takes
up the issue of prime matter from a more metaphysical perspective. In this place, St. Thomas
argues that it pertains more to natural philosophy than to metaphysics to distinguish prime matter
Carl: Metaphysics 64
as the underlying subject of change. He observes that in Book VII, c. 3 of the Metaphysics,
Aristotle establishes the claim that prime matter differs from all forms by using “the method of
predication, which is proper to dialectics and is closely connected with this science.”
In brief, the argument that St. Thomas presents is that one must identify something as the
ultimate subject of which all terms are predicated; not in the sense of univocal predication, but in
the sense of denominative predication, in which the subject and the predicate differ essentially or
in genus. That is, denominative predication is the mode of predication according to which
accidents are predicated of substance (or in general, the mode in which a term from a genus is
predicated of something from outside of that genus). For example:
Man is animal. -univocal or essential predication (man and animal are the same in
genus)
consequence: “Humanity is animality” is also true.
Man is white. -denominative predication (man and white differ in genus)
however: “Man is whiteness” is false, and “Humanity is whiteness” is false.
Now, employing the distinction between univocal or essential predication and
denominative predication, St. Thomas argues that “actual substance is not predicated of matter
univocally or essentially, but denominatively.” As evidence of this, he notes:
This material thing (materiatum) is man. -true
Matter is man. -false
Matter is humanity. -false
Substance is therefore predicated denominatively of matter, just as accidents are predicated
denominatively of substance; and therefore matter does not belong to the genus of substance, and
consequently matter must differ essentially from every substantial form.
8.2. An Examination of Prime Matter as Pure Potentiality
The central claim made by St. Thomas concerning prime matter is that, as a principle of
potency for receiving substantial form and insofar as it is distinct from every form or principle of
actuality, prime matter in itself must be pure potentiality. Prime matter possesses no characteristics
apart from the very potency for receiving substantial form, and in itself it is in potency to receive
any substantial form.64 St. Thomas reaffirms this view frequently throughout his career, asserting
that prime matter is distinct from every form and therefore possesses no positive characteristics of
any kind: it is just the principle of potency for receiving substantial form.
That prime matter should be understood as a principle of pure potency was a controversial
position in the 13th and 14th centuries; it was a common view particularly among the Franciscans
that prime matter must itself possess some degree of actuality apart from its being informed by any
substantial form. As we shall see, as a consequence the thesis that prime matter is pure potency is
closely connected with the thesis that there is only one substantial form in a given substance.
St. Thomas’s arguments for the claim that prime matter is pure potency fall under two
headings: in both cases, his primary concern is typically to defend one of two related claims. The
first related claim is the one we have already examined, which is that matter as such is to be
64One can draw a parallel between prime matter as pure potency and the potential intellect as possessing the
capacity to receive the intelligible likeness of anything that it can know.
Carl: Metaphysics 65
distinguished from any form. The second related claim, as just noted, is the thesis that there is only
one substantial form in any corporeal substance: we will address this claim in the next section of
the course notes. Our concern in this section, therefore, will primarily be just to clarify St.
Thomas’s claim that prime matter is pure potency.
One can find a very large number of texts in which St. Thomas expresses his position that
prime matter is pure potency. For example, In Sent. 1.39.2.2 ad 4:
[A]liquid enim est quod habet esse tantum in
potentia sicut materia prima, et hoc semper habet
defectum, nisi removeatur per aliquod agens
reducens eam in actum.
For there is something which has being (esse) only
in potency, such as prime matter, and this always
has a defect, unless it be removed through some
agent reducing it to act.
In this text, and in others, St. Thomas compares prime matter as pure potency to God as
pure act. In the hierarchy or gradation of being, prime matter is as it were at the opposite extreme
compared to God, with all the beings that involve an admixture of act and potency in between.
In another text, SCG 1.17, St. Thomas argues for the conclusion that there is no matter in
God. In this place he touches on a curious theory advanced by one medieval thinker:
In hoc autem insania David de Dinando
confunditur, qui ausus est dicere Deum esse idem
quod prima materia, ex hoc quod, si non esset
idem, oporteret differre ea aliquibus differentiis, et
sic non essent simplicia; nam in eo quod per
differentiam ab alio differt, ipsa differentia
compositionem facit.
Hoc autem processit ex ignorantia qua nescivit
quid inter differentiam et diversitatem intersit.
Differens enim, ut in X Metaph. determinatur,
dicitur ad aliquid, nam omne differens aliquo est
differens: diversum autem aliquid absolute dicitur,
ex hoc quod non est idem. Differentia igitur in his
quaerenda est quae in aliquo conveniunt: oportet
enim aliquid in eis assignari secundum quod
differant; sicut duae species conveniunt in genere,
unde oportet quod differentiis distinguantur. In his
autem quae in nullo conveniunt, non est
quaerendum quo differant, sed seipsis diversa sunt.
But on this [issue] the madness of David of Dinant
is confounded, who dared to say that God is the
same as prime matter, from this that, if He were
not the same, He would have to differ from it by
some differences, and thus they would not be
simple; for in that which differs from another
through a difference, that difference forms a
composition [with it].
But this [view] proceeds out of ignorance, in that
he did not know what distinguishes difference and
diversity. For the different, as in Metaphysics X, is
said with respect to something, for every difference
is different by something: but something is called
diverse absolutely, from this that it is not the same.
Therefore difference must be sought among those
that agree in something: for it is necessary that
something in them be designated according to
which they differ; as two species share in a genus,
whence it is necessary that they be distinguished
by differences. But among those which share in
Carl: Metaphysics 66
Sic enim et oppositae differentiae ab invicem
distinguuntur: non enim participant genus quasi
partem suae essentiae: et ideo non est quaerendum
quibus differant, seipsis enim diversa sunt. Sic
etiam Deus et materia prima distinguuntur, quorum
unus est actus purus, aliud potentia pura, in nullo
convenientiam habentes.
nothing, that by which they differ is not to be
sought; rather, they are diverse in themselves. For
in this way too opposite difference are
distinguished from one another: for they do not
participate a genus as a part of their essence: and
therefore those things by which they differ are not
to be sought, for they are diverse in themselves. In
this way too God and prime matter are
distinguished, of which one is pure act, the other
pure potency, having agreement in nothing.
Prime matter as pure potency is distinguished from God as pure act not by any difference,
but rather by an absolute diversity. We have already seen Thomas suggest a similar kind of
distinction by absolute diversity between God as ipsum esse per se subsistens and creatures as
instances of participated esse.
What, then, should we say that prime matter is? It is nothing but the potency for substantial
form (and to be precise, for the substantial form of corporeal substances). In any corporeal
substance, St. Thomas contends that we should distinguish between that thing’s substantial form as
the cause that makes the thing to be what it is and its prime matter, which is the principle in it that
receives and limits the substantial form. We will have more to say on this point in consideration of
matter as the principle of individuation.
Prime matter cannot exist independently
As a consequence of prime matter’s being pure potentiality with no formal characteristics,
it should not be a surprise that St. Thomas holds that prime matter cannot exist apart from
composition with a substantial form—and not even by the power of God. It is not possible for
prime matter to exist apart from substantial form, because it is substantial form that communicates
existence to prime matter (not as an efficient cause, but as a formal cause). As St. Thomas puts it in
Summa contra Gentiles II c. 43, in responding to the suggestion that God first created prime matter
and then left it to be informed by other agents: “Prime matter could not have existed by itself prior
to every formed body, since it is not anything except pure potency; for every existent in act is from
some form.”
Indeed, St. Thomas holds that to assert that prime matter could exist by itself apart from
any form would be to assert a contradiction: “To say that matter pre-exists without form is to
express being in act without act, which implies contradiction.”65 Not even by the power of God,
therefore, will St. Thomas allow that prime matter could exist without form, because God cannot
do anything that entails a contradiction. He affirms this position explicitly in Quodlibet 3 q. 1 a. 1:
“Existing non-being, at the same time and in the same respect, is repugnant to the character of
being: therefore that something should at the same time both be and not be, cannot be done by
God, nor something including a contradiction. But for matter to be in act without form is of this
65Summa theologiae I q. 66 a. 1: “Dicere igitur materiam praecedere sine forma, est dicere ens actu sine
actu,: quod implicat contradictionem.”
Carl: Metaphysics 67
kind [i.e., it implies a contradiction].”66
Thus, although St. Thomas recognizes a real distinction and composition between
substantial form and prime matter, this does not imply that prime matter is capable of existing
independently from substantial form. This is a crucially important point for our understanding of
what St. Thomas means by a real distinction: it does not imply the possible separate and
independent existence of the items distinguished. In this, St. Thomas’s position differs from that of
many other medieval theologians and philosophers, who do take real distinction to imply the
possibility of independent existence.
8.3. The Unicity of Substantial Form in Corporeal Substances
The third point that we should address is St. Thomas’s thesis that in a given corporeal
substance there is only one substantial form. This issue is closely connected to the question of
whether or not in man there is only one soul. This latter question was so controversial in the late
13th and early 14th centuries that the remarkable study, Early Thomistic School (by Frederick
Roensch, 1964), distinguishes between followers of St. Thomas and his philosophical opponents
just by the criterion or acceptance or disagreement with this thesis of the unicity of soul or
substantial form.
In brief, the position favored by most Franciscan and secular theologians was that in a
given corporeal substance (and in particular in a human being), there is more than one substantial
form, each one corresponding to a different degree of organization and actuality in the substance.
For example, such a view might posit that in a man there is a substantial form according to which a
man is corporeal, another according to which he is living (a vegetative soul), another according to
which he has sensation (a sensitive soul), and another according to which he is rational (a rational
soul). On this view, the rational soul is only the last of these substantial forms, and one can accept
both that there are multiple substantial forms and even multiple souls in a single individual human
being.
Against such a view, St. Thomas argues that substantial form is what makes a thing to be
what it is, giving it its unity and identity as an instance of a given essential kind. If, therefore, there
were several substantial forms (including souls) in a given substance, that substance would not
truly be one thing of one kind with substantial unity: the unity and identity of a substance depends
upon the unicity of its substantial form.
We can turn to two of the arguments from one of St. Thomas’s extended treatments of the
issue of the unicity of soul in man; but we should note that his reasoning can be extended to the
issue of unicity of substantial form in any substance. This text is SCG 2.58:
Quae attribuuntur alicui eidem secundum diversas
formas, praedicantur de invicem per accidens:
album enim dicitur esse musicum per accidens,
quia Socrati accidit albedo et musica. Si igitur
anima intellectiva, sensitiva et nutritiva sunt
Those which are attributed to the same thing
according to diverse forms, are predicated of one
another per accidens: for white is said to be
musical per accidens, since whiteness and musical
are accidental to Socrates. If therefore the
66Quodlibet 3 q. 1 a. 1: “Repugnat autem rationi entis non ens, simul et secundum idem, existens: unde quod
aliquid simul sit et non sit, a Deo fieri non potest, nec aliquid contradictionem includens. Et de huiusmodi
est materiam esse actu sine forma. . .” See Wippel 324-25.
Carl: Metaphysics 68
diversae virtutes aut formae in nobis, ea quae
secundum has formas nobis conveniunt, de
invicem praedicabuntur per accidens. Sed
secundum animam intellectivam dicimur homines,
secundum sensitivam animalia, secundum
nutritivam viventia. Erit igitur haec praedicatio per
accidens, homo est animal; vel, animal est vivum.
Est autem per se: nam homo secundum quod est
homo, animal est; et animal secundum quod est
animal, vivum est. Est igitur aliquis ab eodem
principio homo, animal et vivum. . . .
intellective, sensitive, and nutritive souls are
diverse powers or forms in us, then those things
which belong to us according to these forms,
would be predicated of one another per accidens.
But according to the intellective soul we are called
men, according to the sensitive [soul we are called]
animals, according to the nutritive [soul we are
called] living. Therefore this predication will be
per accidens: man is animal; or, animal is living.
But this predication is per se: for man insofar as he
is man, is animal; and animal insofar as it is
animal, is living. Therefore it is by the same
principle that one is a man, an animal, and
living. . . .
The essential (per se) predication of all of the parts of the definition of a substance can
only be preserved, on St. Thomas’s view, by the unicity of soul in man (or the unicity of substantial
form in general). Otherwise, what belongs to a thing according to one of its substantial forms
would be accidental to what it is according to another of its substantial forms, with the absurd
consequence that it would be accidental to a man that he be an animal.
Praeterea. Ab eodem aliquid habet esse et
unitatem: unum enim consequitur ad ens. Cum
igitur a forma unaquaeque res habeat esse, a forma
etiam habebit unitatem. Si igitur ponantur in
homine plures animae sicut diversae formae, homo
non erit unum ens, sed plura. Nec ad unitatem
hominis ordo formarum sufficiet. Quia esse unum
secundum ordinem non est esse unum simpliciter:
cum unitas ordinis sit minima unitatum.
Furthermore. Something has being (esse) and unity
from the same [principle]: for one follows upon
being (ens). Since therefore each thing has being
(esse) from form, it will also have unity from form.
If therefore there be posited in man several souls as
diverse forms, man will not be one being, but
several. Nor will an order of forms suffice for the
unity of a man, because to be (esse) one according
to order is not to be (esse) one simply: since unity
of order is the least of unities.
That unity follows upon being is a claim that we will investigate later, in our consideration
of the transcendentals. This is a claim that St. Thomas appropriates from Aristotle: insofar as
something is a being, it is one. Since substance is being in the primary and simple sense, it must be
the case that a substance is one. Now, the substantial form is the cause that makes the substance to
be what it is, and for this reason St. Thomas says that it is from the form that each thing has esse. If
therefore there were several substantial forms (or souls) in a thing, then that thing would not be one
thing, but several.
Carl: Metaphysics 69
St. Thomas also excludes the suggestion that a plurality of substantial forms could make a
thing to be one through a unity of order. A unity of order is the way in which, for example, the
members of an army or students in a class are one. If there were a unity of order among some
group of substances simply according to their substantial forms, one would have many substances
unified by order, and not one substance simply.
For St. Thomas, the unicity of substantial form in every substance is a general
metaphysical thesis; it is not a claim restricted to the issue of the soul. A thing must have one
substantial form in order to be one substance.
The problem of proximate matter and the mixture of the elements
Although St. Thomas holds strictly to the thesis that there is only one substantial form in a
given substance, nevertheless he also holds to such claims as the following:
(1) The particular matter out of which a given substance is generated can have an effect on
the characteristics of the resulting substance. That is, one substance can have different qualities
from another substance that can only be accounted for in differences in their matter that in a way
pre-existed the substances themselves.
(2) In general, St. Thomas allows that one can account for the characteristics of certain
substances (such as living things) from their being composed from contraries, i.e., from the
elements, which are themselves distinguished by their contrary qualities. For example, St. Thomas
repeatedly claims that living things are corruptible and mortal because they are composed from the
elements.
Now, if substantial change has prime matter as a subject, and if prime matter has of itself
no positive characteristics, then it seems impossible that any of the characteristics of the matter
from which a substance comes to be should make any difference in the characteristics of the
resulting substance. Even in general, to claim that any substance that results from the mixture of
the elements will be naturally subject to corruption seems odd, if the substantial forms of the
elements themselves do not remain in the resulting substance.
St. Thomas presents his solution to these solutions in the brief work De mixtione
elementorum, which was composed as a letter responding to an inquiry made to St. Thomas by
Phillip de Castro Caeli, a professor of medicine. In the medical theory of the time, the theory of the
four humors was understood to be based upon the theory of the four elements: each of the bodily
humors corresponded to one of the four elements. Apparently aware of St. Thomas’s position about
the unicity of substantial form, Phillip asked Thomas for clarification about the way in which it can
be said that the elements remain in the substances composed from them.
In his reply, St. Thomas excludes the possibility that in any way the substantial forms of
the elements should remain in any resulting mixed substance composed from the elements,
offering the same sorts of reasons we have already encountered. He criticizes other proposals for
how to solve the dilemma, and finally he presents his own solution towards the end of the work.
That St. Thomas shares Phillip’s concern (that somehow the elements must be preserved in a mixed
body in order for it to even make sense to say that the resulting substance is a mixed body) is
indicated by his introduction to his own solution:
Oportet igitur alium modum invenire, quo et
veritas mixtionis salvetur, et tamen elementa non
It is necessary therefore to find another way in
which both the truth of mixtures be preserved, and
Carl: Metaphysics 70
totaliter corrumpantur, sed aliqualiter in mixto
remaneant.
nevertheless the elements are not entirely
corrupted, but somehow remain in the mixture.
St. Thomas proceeds to note that the qualities of the elements are distinct from the
elemental bodies themselves, and insofar as the elements act upon one another, a given elemental
body can have more or less of its characteristic qualities. There can therefore result from the
accidental mixture of the elements bodies with qualities that are a medium, relative to the qualities
characteristic of the elements themselves.
Now, following Aristotle, St. Thomas contends that alterations—qualitative changes—are
dispositive to substantial changes. The only sense in which substantial change is a process is
insofar as certain qualitative changes precede the moment of substantial change (but a substantial
change in itself occurs in an instant). It is insofar as a body possesses certain qualities that it is
capable of receiving a given substantial form.
Concerning the mixture of the elements, therefore, St. Thomas argues that by their
(initially accidental) mixture, the elements produce mixed bodies with qualities that are dispositive
to the reception of a given substantial form. At the moment of substantial change, it is the prime
matter of the elements that is the true subject of the change. Nevertheless, the qualities that were
preparatory in the body for the reception of the substantial form remain in the new substance, just
insofar as these qualities are the proper qualities of the new substance. The new substance is what
it is by virtue of its substantial form, but there remain in it the qualities that were dispositive to the
reception of that substantial form: and these qualities are now proper qualities in the new substance
as their subject. Since they are qualities of the new substance, they receive their being from the
substance.
As regards the elements in particular, therefore, St. Thomas contends that the elements
remain not actually but virtually in the substances that come to be from the mixture of the
elements. That is, in a given mixed substance, there is no earth, air, fire, or water actually: but the
elements remain insofar as their characteristic powers (which are their qualities) remain in the
mixed body as qualities of the new substance.
This account allows for the possibility of variation in the matter out of which a given
substance comes to exist, with a consequence on the particular characteristics of the resulting
substance. This can occur insofar as the qualities dispositive to the reception of a given substantial
form will admit of a range of possibilities.
8.4. The Principle of Individuation
A famous question for medieval philosophers and theologians concerned the principle
according to which members of a species differ numerically from one another. It was generally
accepted, from the background provided by Porphyry’s Isagoge, that what distinguishes something
specifically from other members of its genus is the specific difference. However, while it was taken
for granted that members of a species differ only numerically, there was some measure of dispute
about the principle that serves to set apart one individual from another member of the same
species.
Designated matter as the principle of individuation
The background for the claim that matter is the principle of individuation is found in two
passages from Aristotle’s Metaphysics.
Carl: Metaphysics 71
(1) The first text comes from Metaphysics 5.6 1016b31-32, which begins with a distinction
among kinds of unity:
In this text, Aristotle points to unity of matter as what accounts for the numerical unity of
an individual: by contrast, unity of intelligible structure is what accounts for specific unity among
two or more individuals.
In commenting on this text (lec. 8), St. Thomas writes as follows:
Ponit aliam divisionem unius, quae est magis
logica; dicens, quod quaedam sunt unum numero,
quaedam specie, quaedam genere, quaedam
analogia. Numero quidem sunt unum, quorum
materia est una. Materia enim, secundum quod stat
sub dimensionibus signatis, est principium
individuationis formae. Et propter hoc ex materia
habet singulare quod sit unum numero ab aliis
divisum. Specie autem dicuntur unum, quorum una
est ratio, idest definitio. Nam nihil proprie
definitur nisi species, cum omnis definitio ex
genere et differentia constet. Et si aliquod genus
definitur, hoc est inquantum est species.
He offers another division of one, [a division] that
is more logical [in character]; saying, that some
things are one in number, others in species, others
in genus, others by analogy. Indeed those are one
in number of which the matter is one. For matter,
insofar as it stands under designated dimensions, is
the principle of the individuation of form. And
because of this a singular thing has that it is one
and divided from others from matter. But those are
called one in species, of which there is one ratio,
that is the definition. For nothing is properly
defined except a species, since every definition is
composed from genus and difference. And if some
genus is defined, this is insofar as it is a species.
St. Thomas interprets this text from the Metaphysics as supporting the claim that it is the
matter of a thing that ultimately accounts for the individuation of form. We will comment below on
the significance of the qualification “insofar as it stands under designated dimensions.”
(2) The second text is Metaphysics 7.8 1033b29-1034a8. In this text, Aristotle is arguing
against the need to posit separate Forms as exemplars or principles of generation:
Further, some things are one in number, some in species, some in genus, and some analogically or
proportionally. Those things are one in number which have one matter; in species, which have one
intelligible structure; in genus, which have the same figure of predication; and proportionally,
which are related to each other as some third thing is to a fourth.
Carl: Metaphysics 72
Aristotle contends that one does not need to posit a separate Form to account for the
generation of a given member of a species; rather, an individual animal is sufficient as a principle
of generation for another animal of the same species. It is not the form as such that is generated,
but rather than individual, which is a form in matter, that is, the composite of form and matter.
St. Thomas comments on the latter portion of this text (lec. 7):
“Omnis autem species, quae est in materia,”
scilicet in his carnibus et in his ossibus, est aliquod
singulare, ut Callias et Socrates. Et ista etiam
species causans similitudinem speciei in generando
est diversa a specie generati secundum numerum
propter diversam materiam. Cuius diversitas est
principium diversitatis individuorum in eadem
specie. Diversa namque est materia, in qua est
forma hominis generantis et hominis generati. Sed
utraque forma est idem secundum speciem. Nam
“But every species, which is in matter,” namely in
this flesh and in these bones, is something singular,
such as Callias or Socrates. And so too this
form/species causing a likeness in species by
generating is diverse in according to number from
the species of the generator, because of diverse
matter. The diversity [of matter] is the principle of
the diversity of individuals in the same species. For
diverse is the matter in which is [found] the form
of the man generating and the form of the man
And in some cases, it is evident that the thing which generates is of the same kind as the thing
which is generated, although they are not the same numerically but specifically, for example, in the
case of natural generations (for man begets man), unless something contrary to nature is generated,
as when a horse begets a mule. And even these cases are alike; for what is common to both horse
and ass as their proximate genus has no name, but perhaps both might be something like mule.
Hence there is evidently no need to furnish a Form as an exemplar; for men would have searched
for Forms especially in sensible things, since these are substances in the highest degree. But the
thing which generates is adequate for producing the thing and for causing the form in the matter.
And when the whole is such and such a form in this flesh and these bones, this is Callias or
Socrates; and they differ in their matter (for the matter of each is different) but are the same in
form, because form is indivisible.
Carl: Metaphysics 73
ipsa species est “individua,” idest non
diversificatur in generante et generato. Relinquitur
ergo, quod non oportet ponere aliquam speciem
praeter singularia, quae sit causa speciei in
generatis, ut Platonici ponebant.
generated. But each form is the same according to
species. For the form/species itself is “indivisible,”
that is, it is not diversified in the one who
generates and the one generated. It follows
therefore that it is not necessary to posit some
Form/species apart from singulars, which is the
cause of the form/species in [things] generated, as
the Platonists claimed.
The species of Socrates and the species of Callias taken as such do not differ: the species is
what is understood to be the same in both Socrates and Callias. However, the form of Socrates
does differ from the form of Callias, insofar as Socrates has this form and Callias has that form,
even if those forms are the same according to species. It is the matter of each that accounts for the
diversification of form. Socrates and Callias differ insofar as this matter is in Socrates, while that
matter is in Callias.
It is helpful to emphasize precisely what is at issue when it is said that designated matter is
the principle of individuation. Matter is said to individuate insofar as it serves to distinguish the
individual from other members of the species. But for St. Thomas (but perhaps not for Aristotle
himself), matter taken universally or abstractly is included in a thing’s essence: that is, the species
(which is what is defined) includes in its definition matter taken universally. Therefore, it is not
matter taken abstractly that is the principle of individuation: it is designated matter, which is to say
this matter as opposed to that matter. It is in this way that St. Thomas consistently contends that
designated matter is the principle of individuation.
Matter under determinate dimensions vs. matter under indeterminate dimensions
Having considered what St. Thomas consistently says throughout his career—that
designated matter is the principle of individuation—we can now turn to a brief consideration of a
more particular issue that St. Thomas seems to have re-thought a number of times during his
career. We can understand the question at issue in this way: what beyond matter taken in itself
(which is to say, matter taken universally or abstractly) suffices to individuate form? That is, what
is it that distinguishes designated matter from undesignated matter? We will consider two
representative texts and then explain what is at issue in this question.
We can take as representative of the view that designated matter is matter under
determinate dimensions St. Thomas’s comments in De ente et essentia c. 2:
Sed quia individuationis principium materia est, ex
hoc forte videretur sequi quod essentia, que
materiam in se complectitur simul et formam, sit
tantum particularis et non universalis: ex quod
sequeretur quod universalia diffinitionem non
haberent, si essentia est id quod per diffinitionem
significatur. Et ideo secundum est quod materia
But since the principle of individual is matter, from
this indeed it would seem to follow that the
essence, which includes in itself both matter and
form, is only particular and not universal: from
which it would follow that universals would not
have a definition, if the essence is that which is
signified through a definition. And therefore it
Carl: Metaphysics 74
non quolibet modo accepta est individuationis
principium, sed solum materia signata; et dico
materiam signatum que sub determinatis
dimensionibus consideratur. Hec autem materia in
diffinitione que est hominis in quantum est homo
non ponitur, sed poneretur in diffinitione Sortis si
Sortes diffinitionem haberet. In diffinitione autem
hominis ponitur materia non signata: non enim in
diffinitione hominis ponitur hoc os et hec caro, sed
os et caro absolute que sunt materia hominis non
signata.
follows that matter taken in every way is not the
principle of individuation, but only designated
matter; and I call designated matter that which is
considered under determinate dimensions. But this
matter is not put in the definition which is of man
insofar as he is man, but it would be put in the
definition of Socrates if Socrates had a definition.
But in the definition of man is placed undesignated
matter: for this flesh and this bone are not put in
the definition of man, but flesh and bone
[considered] absolutely, which are the
undesignated matter of man.
In this text, we find St. Thomas apparently defining designated matter as matter under
determinate dimensions: that is, matter insofar as it is subject to a precise dimensive (i.e.,
continuous) quantity. That is, here designated matter seems to be understood as “this much matter”
or “matter with these dimensions.”
As representative of the view that the principle of individuation is matter under
indeterminate dimensions, we can take St. Thomas’s comments from In DT 4.2:
Non enim forma individuatur per hoc quod
recipitur in materia, nisi quatenus recipitur in hac
materia distincta et determinata ad hic et nunc.
Materia autem non est divisibilis nisi per
quantitatem. Unde philosophus dicit in I
physicorum quod subtracta quantitate remanebit
substantia indivisibilis. Et ideo materia efficitur
haec et signata, secundum quod subest
dimensionibus.
Dimensiones autem istae possunt dupliciter
considerari. Uno modo secundum earum
terminationem; et dico eas terminari secundum
determinatam mensuram et figuram, et sic ut entia
perfecta collocantur in genere quantitatis. Et sic
non possunt esse principium individuationis; quia
cum talis terminatio dimensionum varietur
frequenter circa individuum, sequeretur quod
For form is not individuated through this that it is
received in matter, except insofar as it is received
in this distinct matter, determined to the here and
now. But matter is not divisible except by quantity.
Whence the Philosopher says in Physics I that
quantity removed, [only] indivisible substance will
remain. And therefore matter is rendered this and
designated, insofar as it is under dimensions. But
those dimensions can be considered in two ways.
In one way, according to their termination: and I
call them terminated according to determinate
measure and figure, and so, as complete beings,
[dimensions] are located in the genus of quantity.
And in this way they cannot be the principle of
individuation; since such termination of
dimensions will vary frequently as regards an
individual, [so that] it would follow that the
Carl: Metaphysics 75
individuum non remaneret semper idem numero.
Alio modo possunt considerari sine ista
determinatione in natura dimensionis tantum,
quamvis numquam sine aliqua determinatione esse
possint, sicut nec natura coloris sine
determinatione albi et nigri; et sic collocantur in
genere quantitatis ut imperfectum. Et ex his
dimensionibus indeterminatis materia efficitur
haec materia signata, et sic individuat formam, et
sic ex materia causatur diversitas secundum
numerum in eadem specie.
individual would not always remain the same in
number. In another way [dimensions] can be
considered without that determination, [and] only
in the nature of dimension, although they can never
exist without some determination, just as the nature
of color [cannot exist] without determination to
white or black; and in this way [dimensions] are
located in the genus of quantity as incomplete. And
by these indeterminate dimensions matter is made
this designated matter, and thus it individuates
form, and thus diversity according to number in the
same species is caused by matter.
It would seem that St. Thomas’s primary concern in drawing the distinction between
determinate dimensions and indeterminate dimensions is answering the objection that if designated
matter is the principle of individuation, then insofar as something’s matter changes quantity, it
would lose its numerical identity with itself over time. By saying that it is matter under
indeterminate dimensions that individuates form, St. Thomas can answer such an objection.
However, as we have seen, in other texts, St. Thomas explicitly says that it is matter under
determinate dimensions that serves as the principle of individuation.
As Msgr. Wippel details, St. Thomas seems to have fluctuated between these two opinions
earlier in his career, before generally abandoning the distinction between determinate dimensions
and indeterminate dimensions; when he says anything explicitly on the point in his later texts, it is
in favor of matter under determinate dimensions—or, as we saw in the text from the Commentary
on the Metaphysics, matter under designated dimensions. It would seem then that the view
expressed in the De ente et essentia c. 2 would seem to have been St. Thomas’s mature view on the
issue.
Carl: Metaphysics 76
9. Comparison and Coordination of the Modes of Composition: Potency and Act
As we have seen, in the thought of St. Thomas we can identify three different modes or
levels of composition in the beings that fall under ens commune, the subject of metaphysics. These
are essence-esse composition, substance-accident composition, and matter-form composition. The
former two modes of composition pertain to all of the beings that fall under ens commune, whereas
the third mode pertains only to corporeal substances.
We have seen a variety of approaches, some depending more on logic and others on
argumentation more proper to natural philosophy, for establishing each of these three modes of
composition. We have spent much time attending to details of St. Thomas’s various arguments for
these conclusions, and we have attended to a number of ancillary issues connected with each of the
modes of composition.
In my view, an appreciation of the role that each of these modes of composition plays in
the metaphysical thought of St. Thomas is not complete without consideration of the ways in
which these modes of composition are connected with one another. Therefore, at this point, we will
take up, at least in brief, the work of comparing and coordinating the three modes of composition.
This will allow us to better understand each of the three modes of composition; it will also allow us
to begin to see how St. Thomas’s metaphysical thought hangs together in a systematic way.
9.1. Essence-esse Composition: Coordination with the other Modes of Composition
To begin, we can focus on the most fundamental mode of composition found in ens: this is
the composition of essence and existence or the act of being. To spell out more explicitly
something we have suggested above, we can note that by this thesis, St. Thomas rules out three
possibilities:
(1) St. Thomas wishes to exclude that a thing’s existence or act of being is just one of the
intelligible notes belonging to its essence. It cannot be that a thing’s existence is one of the parts of
the essence: a thing’s existence is never even in a partial way an answer to the question, “what is
it?,” where the answer to this question is just what we mean by essence. That esse is not a part of
essence is the ultimate reason why esse is known not through apprehension, which regards what a
thing is, but rather through judgment. However, insofar as there are parts of the essences that we
understand, this is grounded in matter-form composition.
(2) St. Thomas also wishes to exclude that a thing’s existence or act of being is an accident
that is added to its substance, understood as the subsisting subject. Such a possibility must be
excluded because a substance must already exist in order to be the subject of any accidents: its very
existence or act of being therefore cannot be just one among its many accidents.
(3) St. Thomas also wishes to exclude that any finite thing’s essence is nothing but
existence or the act of being. In his arguments supporting the thesis that there could only be one
being in which essence and esse are identical, it is this way of approaching essence-esse distinction
that is emphasized.
The first and third of these claims excluded by St. Thomas invite us to offer some
comparison between essence-esse composition and (a) matter-form composition. The second claim
invites comparison with (b) substance-accident composition.
Essence-esse and matter-form composition compared; forma dat esse
Carl: Metaphysics 77
The essences knowable by human beings—that is, the essences of corporeal substances—
are composite, even though a thing’s existence or act of being is not one of the parts of the essence.
Rather, the parts of the definition of the essence are taken from the matter and form of the
substance: in particular, the genus is taken from a thing’s (proximate) matter and the difference is
taken from the substantial form. For example, in the definition of man as rational animal, the genus
animal is taken from what man shares in common materially with other sensitive living things,
while the difference rational is taken from the special character of the human soul, which is the
substantial form of the human being.
As St. Thomas repeatedly emphasizes, the knowledge of what a corporeal thing is includes
the matter of the thing, taken abstractly or universally. For example, knowledge of what a man is
includes a knowledge of flesh and bones (which are, it should be noted, common to man and to
some other animals) taken abstractly or universally. But it is designated matter—this flesh and
these bones—that serves to individuate form and to distinguish the individual numerically from
other members of the species. Form can be taken universally as the essence (the forma totius or
form of the whole), in which case it includes only matter taken abstractly; or form can be taken as
this substance’s form, which is individuated by the matter with which it forms a composite (this is
the forma partis, the substantial form of the individual substance).
Given all of this, the question should arise: what is the relationship between essence-esse
composition and matter-form composition? While these might appear to be two totally unrelated
different aspects according to which a given being (ens) can be analyzed, I would emphasize the
importance of the connection between them. We can address this issue by a brief examination of
the axiom forma dat esse: form gives being.
The general understanding of any formal cause is that it is what makes a thing to be what it
is. One must posit a formal cause, in general, because one recognizes sameness of kind in
numerically distinct individuals. The relationship between form and esse can first be appreciated
just by emphasizing two elements of this description of the formal cause: the formal cause makes a
thing (a) to be (b) what it is.
(a) Matter, taken in itself, does not and cannot exist independently: not even by the power
of God does St. Thomas think it possible for prime matter to exist independently. Matter only
exists insofar as it is informed by substantial form. It is therefore the formal cause that causes
matter to be, to exist. “Form gives being” by giving being to matter. One will find St. Thomas
speaking in this way in a special way about the human soul: he says that the human souls
communicates being (esse) to the body.
(b) In “giving being” to matter, a formal cause always causes being of a specific and
therefore limited kind: what results from matter-form composition is a being that can be placed
under the genus of substance and under a species according to the differentiating characteristic that
it shares in common with other members of its species. By being this kind, the resulting substance
is not of another kind. Accordingly, forma dat esse should be understood in conjunction with the
claim that the substantial form limits and determines the kind of being possessed by the resulting
subject. By actualizing matter, which is a principle of potency, substantial form is the principle that
accounts for the limited, determined way in which the resulting substance exists.
Relative to the act of being or existence (esse), therefore, the substantial form is a limiting
principle. This should be understood as a companion to the claim that in general it is essence that
limits or determines the act of being. In other words, of the parts of a corporeal essence (form and
matter), it is form rather than matter that should be understood as the principle that limits existence
Carl: Metaphysics 78
or the act of being.67
Essence-esse and substance-accident composition
Whereas matter-form composition is found only in corporeal substances, St. Thomas holds
that substance-accident composition is found in all of those beings in which there is a composition
of essence and esse. What, then, is the connection between these two modes of composition? Why
is it that everything in which essence is not identical with esse also admits of a composition of
substance and accident? To address this point, we can consider St. Thomas’s arguments in ST
1.54.1 for the conclusion that in an angel, the act of understanding is distinct from the angel’s
substance.
Respondeo dicendum quod impossibile est quod
actio Angeli, vel cuiuscumque alterius creaturae,
sit eius substantia. Actio enim est proprie actualitas
virtutis; sicut esse est actualitas substantiae vel
essentiae. Impossibile est autem quod aliquid quod
non est purus actus, sed aliquid habet de potentia
admixtum, sit sua actualitas, quia actualitas
potentialitati repugnat. Solus autem Deus est actus
purus. Unde in solo Deo sua substantia est suum
esse et suum agere.
Praeterea, si intelligere Angeli esset sua substantia,
oporteret quod intelligere Angeli esset subsistens.
Intelligere autem subsistens non potest esse nisi
unum; sicut nec aliquod abstractum subsistens.
Unde unius Angeli substantia non distingueretur
neque a substantia Dei, quae est ipsum intelligere
subsistens; neque a substantia alterius Angeli.
Si etiam Angelus ipse esset suum intelligere, non
I respond by saying that it is impossible that the
action of an Angel, or of any other creature
whatsoever, be its substance. For action is the
proper actuality of a power; just as esse is the
actuality of a substance or essence. But it is
impossible that something which is not pure act,
but has something of potency admixed, should be
its actuality, since actuality is opposed to
potentiality. But God alone is pure act. Therefore
in God alone, His substance is His esse and his
action.
Furthermore, if the understanding of an Angel were
its substance, it would be necessary that the
understanding of an Angel be subsistent. But
subsistent understanding cannot be but one; as
neither [is] something abstract subsistent.
Therefore the substance of one Angel would not be
distinguished either from the substance of God,
which is the subsistent understanding itself; nor
from the substance of another Angel.
Also, if an Angel itself were its understanding,
67
On the other hand, relative to the substantial form, designated matter is also a limiting principle. However,
it should not be understood as a principle limiting the act of being itself, but as a principle limiting the
essence taken as universal to this individual. As a consequence, one can affirm that distinct members of a
given species participate in the act of being taken in common (esse commune) to the same degree, even if
one must deny that ens is predicated univocally of these individuals, because the esse of this individual is not
the esse of that individual. As Msgr. Wippel details at the end of c. 9, Fr. Joseph Owens has argued that in the
order of reality, it is ultimately a substance’s esse, which is caused by God, that is the principle of
individuation: here the emphasis is not on individuality as numerical difference from other members of a
species, but on individuality as a thing’s independent existence as such.
Carl: Metaphysics 79
possent esse gradus in intelligendo perfectius et
minus perfecte, cum hoc contingat propter
diversam participationem ipsius intelligere.
there could not be grades in understanding more
and less perfectly, since this occurs on account of
the diverse participation of understanding itself.
Certain aspects of these arguments do presuppose God’s existence as pure act, which we
have not yet considered in this course; and so we will not belabor defense of the argumentation
found here. We only need to highlight that even as regards angels and the acts that they perform
just insofar as they are intelligent substances, St. Thomas denies that there can be an identity
between the activity of understanding and the substance of the angel. That is, substance-accident
composition immediately follows, for St. Thomas, from essence-esse composition.
Carl: Metaphysics 80
9.2. Difference and Identity in Real Composition
At this point, we will conclude our consideration of the modes of composition found in ens
commune by considering two texts that I would argue should guide our understanding of the
meaning of composition in the thought of St. Thomas. The first of these texts distinguishes two of
the modes of composition from the other with respect to the character of the otherness or
difference between the paired principles of composition. The second text will express the identity
of the principles of composition in terms of potency and act.
Difference in the principles of composition
In Quodlibet II q. 2 a. 1, St. Thomas takes up the question of whether angels are composed
in their substance of essence and esse. The first objection is as follows:
Videtur quod angelus non componitur
substantialiter ex essentia et esse. Essentia enim
angeli est ipse angelus, quia quiditas simplicis est
ipsum simplex; si ergo angelus componeretur ex
essentia et esse, componeretur ex se ipso et alio;
hoc autem est inconveniens; non ergo
substantialiter componitur ex essentia et esse.
It seems that an angel is not substantially
composed of essence and existence (esse). For the
essence of an angel is the angel itself, since the
quiddity of [something] simple is itself simple; if
therefore the angel were composed of essence and
existence (esse), it would be composed of itself
and something else; but this is unfitting; therefore
it is not substantially composed from essence and
existence (esse).
This argument rests upon two claims, the first of which we have explicitly encountered
before: (1) the essence of an angel or separate substance is not composed (that is, composed of
matter and form); and (2) in an angel there is no real distinction of essence and supposit. This latter
is a claim that St. Thomas affirms throughout his career; however, in the very next article of this
Quodlibet II q. 2, he carefully distinguishes the sense in which in an angel nature or essence and
supposit can be said to differ.68 We do not need to dwell on this difficult issue at this point, but I
would argue that the text we are considering (Quodlibet II q. 2 a. 1 ad 1) can provide some helpful
insight for reading a. 2.
From these two claims, the first objection concludes that an angel cannot be composed
from essence and esse, because this would be to suggest that it is composed from itself (its
essence) and something else. St. Thomas replies to this objection as follows:
Ad primum ergo dicendum quod aliquando ex hiis
que simul iunguntur relinquitur aliqua res tertia,
sicuti ex anima et corpore constituitur humanitas,
To the first therefore it must be said that sometimes
from these [principles] which are joined together
there results some third thing, just as the humanity
68See Wippel 243-51 for extended discussion of Quod. 2.2.2 and the question of whether or not its doctrine
can be reconciled with St. Thomas’s earlier position. In brief, St. Thomas defends a real distinction of
essence and supposit in every creature (including angels) insofar as every creature as a substance is the
subject of accidents: there are therefore things that every created substance is (according to its accidents)
that are not identical with its essence.
Carl: Metaphysics 81
que est homo, unde homo componitur ex anima et
corpore; aliquando autem ex hiis que simul
iunguntur non resultat res tertia, sed resultat
quedam ratio composita, sicut ratio hominis albi
resolvitur in rationem hominis et in rationem albi,
et in talibus aliquid componitur ex se ipso et alio,
sicut album componitur ex eo quod est album et ex
albedine.
which is a man is constituted from soul and body;
wherefore a man is composed from soul and body.
But sometimes from these [principles] which are
joined together there does not result a third thing,
but there results a certain composite notion (ratio),
just as the notion (ratio) of white man is resolved
into the notion (ratio) of man and the notion (ratio)
of white, and in such [composites] something is
composed from itself and another, just as a white
thing is composed from that which is white and
whiteness.
Here St. Thomas replies to the objection (that angels cannot be composed from essence
and esse because this would be the composition of the angel itself with something else) by arguing
that in the case of substance-accident composition, one does have the composition of something
itself with another: what results from substance-accident composition is not a third thing besides
the substance itself or its accident, but the substance existing in a particular way. St. Thomas thus
calls “white man” a ratio composita (a composite notion), insofar as in the order of reasoning one
resolves “white man” into the notions of “man” (a substance) and “white” (an accident). This is not
to say that substance-accident composition is not a real composition; rather, it is only to deny that
what results from such composition is not a third thing distinct from the substance itself.
St. Thomas holds that the composition of soul and body in man is the composition of two
principles that results in a “third thing” distinct from either the soul or the body taken by
themselves. Socrates is a third thing, relative to his formal cause and his material cause.69 But
white Socrates or ugly Socrates is not a third thing: it is just Socrates existing in a particular way.
So too, in the case of an angel, we can say that the existing angel is not some third thing distinct
both from the angel’s existence and from its essence: rather, it is the angel itself, existing.
Thus, one can say that existence is, as it were, something accidental to essence in finite
beings. St. Thomas draws this conclusion explicitly in the body of Quod. 2.2.1:
Sic ergo in angelo est compositio ex essentia et
esse, non tamen est compositio sicut ex partibus
substantiae, sed sicut ex substantia et eo quod
adheret substantiae.
Therefore there is in an angel composition of
essence and existence (esse); nevertheless, there is
not a composition as from the parts of the
substance, but as from the substance and that
69I have a suspicion that the example of this man being a third thing relative to body and soul may be a
consequence of the peculiar case of the human soul, which is specially created and infused by God, rather
than insofar as this is an example of matter-form composition in general. The next text we will
consider—which concerns the way in which matter and form can be identified—could be seen as
supporting this suspicion. Nevertheless, I present this text from Quod. 2.2.1 ad 1 as Msgr. Wippel
presents it (pp. 103-104), taking the composition of human soul and body as an example of the
composition of form and matter in general.
Carl: Metaphysics 82
which adheres to the substance.
This is not to say that existence is, strictly speaking, an accident. However, the
composition of essence and esse is like substance-accident composition, in that in both cases what
results from the composition is just the substance itself, existing (1) at all (according to its esse)
and (2) in particular ways (according to its accidents).
This text highlights for us what we should not take composition to mean: it does not mean
that the principles from which a thing is composed are themselves things distinct from the
composite. This is the foundation for a claim that we have repeated previously: composition from
principles does not necessarily imply the possibility of separation or independent existence on the
part of the principles.
In the case of essence-esse composition, neither the essence nor the esse of any being (ens)
ever exist independently of one another: indeed, we can see that this would be a contradiction in
terms, to say that something exists without its existence or that its existence exists without that of
which it is the existence.
Identity even in matter-form composition
In the text we have just considered, we have seen a contrast drawn between substanceaccident and essence-esse composition on the one hand and matter-form composition on the
other.70 The real difference between matter and form seems stronger, insofar as what results from
their composition is described as a third thing (tertia res). As a counterweight to this text, we
should consider a remark that St. Thomas offers in In Meta. 8.5:
Sed sicut dictum est, ultima materia, quae scilicet
est appropriata ad formam, et ipsa forma, sunt
idem. Aliud enim eorum est sicut potentia, aliud
sicut actus. Unde simile est quaerere quae est
causa alicuius rei, et quae est causa quod illa res sit
una; quia unumquodque inquantum est, unum est,
et potentia et actus quodammodo unum sunt. Quod
enim est in potentia, fit in actu.
But as has been said, the ultimate matter, which
namely is appropriated to form, and the form itself,
are the same. For one of these is as potency, the
other as act. Wherefore to ask what the cause of
some thing is, is similar [to asking] what is the
cause that makes that thing be one; because each
thing insofar as it is, is one, and potency and act in
a certain respect are one. For what is in potency, is
made [to be] in act.
Matter and form are composed and really distinct, and yet nevertheless one can also affirm
that in this corporeal substance the form is the matter: because form is just the actualization of
matter taken as a principle of potency. What the matter taken in itself is potentially, the form is
actually. Potency and act are correlated therefore in such a way that one should think of act, in
composite things, always as the actualization of potency.
Potency and act
70As noted in the previous footnote, I have some suspicion that perhaps the previous text’s remarks about
matter-form composition might be restricted only to the example offered, i.e., the body-soul composition
of a human being. Nevertheless, in any event the text we will now consider offers an important
counterweight concerning matter-form composition.
Carl: Metaphysics 83
Having considered the three modes of composition found in ens commune, it is necessary
at this point to offer the general observation that in each case, one can compare the two principles
of composition as principles of potency and act, respectively:
Act : Esse Form Accident
______ _______ ______ ________
Potency : Essence Matter Substance
We can offer the following general conclusions about potency-act composition in general:
(1) In emphasizing that these are cases of real distinction, we mean to affirm that this
distinction of principles is not totally dependent upon or posterior to the activity of the mind
distinguishing.
(2) As we have just seen, even in the case of matter-form composition, one should affirm
in general that form as act is just the actualization of matter as potency. In general, act in a
composite of potency and act is always potency actualized.
(3) In each of the cases of composition we have studied, we have been able to note that the
potency principle is a principle of reception and limitation. The principle of potency in each of the
cases of composition is the principle that accounts for the limited and determined manner in which
the actuality in question is realized. It is in this way that in each case, the principle of potency is
said to participate its act principle.
(4) As we have repeatedly emphasized, composition and real distinction do not imply real
separability or the possible independent existence of the principles distinguished. However, it can
be said that in the case of substance-accident composition, the substance can exist independently of
a given separable accident. Also, in the case of matter-form composition, prime matter is the
subject of substantial change; it is not separable in the sense of being capable of independent
existence, but it is capable of serving as the matter of a different substance.
Carl: Metaphysics 84
10. The Transcendentals
One of the most famous doctrines of Thomistic metaphysics (and indeed of medieval
metaphysics in general) is the theory of the transcendentals, which are the most common properties
of all the things that exist.
10.1. General Statement of the Theory of the Transcendentals
According to this theory, the following terms are common to every being in the categories:
being (ens), one (unum), true (verum), good (bonum), as well as (in some presentations) thing (res)
and something (aliquid). As we will see, St. Thomas holds that whatever exists shares in all of
these most common characteristics, and that in general the distinction between the transcendentals
is a distinction of reason rather than a real distinction. These most common properties are called
transcendental because they “transcend” the categories: that is, they are not limited to any one
category but are found in all of them.
It should be noted, at the start, that being (ens) is itself a transcendental: whatever is (or
exists) is a being. Ens as a transcendental is none other than what we have already called ens
commune, being in general, the being analogically common to all of the categories. We need not
say anything more about ens as a transcendental, given everything that has already been said about
ens commune.
A caveat
In giving a relatively brief consideration of the topic of the transcendentals, we are already
departing from the manner in which a number of authors have presented Thomistic metaphysics; I
speak of those who strongly emphasize the doctrine of the transcendentals as being as it were the
centerpiece of Thomistic metaphysics.71 Often in connection with this tendency, there arises a way
(different from that which has been proposed in this course) of explaining the very project of
metaphysics. One can express the project of an Aristotelian science by noting that it sets forth the
essence of its subject and then proceeds to demonstrate the properties of the subject, and one way
of conceiving of the project of metaphysics is that what it does is to demonstrate and examine
being’s properties, understood as the transcendentals.
While the doctrine of the transcendentals is very important in the teaching of St. Thomas, I
do not think that the transcendentals play quite this role in the project of metaphysics: they are not
the properties of being that are demonstrated by the science of metaphysics.72 After all, ens itself is
one of the transcendentals or most common things. I think it is better to say just that the
transcendentals belong to the subject of metaphysics, just as St. Thomas says that unity, act, and
potency are part of what is studied under ens commune by the metaphysician.
10.2. The De veritate on the Transcendentals
71For just one recent example of this tendency, see Jan Aertsen, Medieval Philosophy and the
Transcendentals: The Case of Thomas Aquinas, (New York: Brill, 1996).
72I would contend instead that the properties of ens commune demonstrated in metaphysics are its various
modes of composition and its dependence upon uncreated being.
Carl: Metaphysics 85
The classic text in which St. Thomas spells out in a systematic way his understanding of
the transcendentals is De veritate q. 1 a. 1, which asks what truth is (quid est veritas?) and whether
the truth is in every way the same as being (ens). He argues that it seems that the true is in every
way the same as being, and in the seventh objection arguing for this view, he argues as follows:
The problem that St. Thomas raises here—the problem of the addition to being—is the
same problem pointed out in our earlier explanation of why being cannot be a genus: it cannot be
the case that anything extraneous is added to being, because what is extraneous to being is nonbeing.
In the first sed contra of this article, St. Thomas writes:
A “nugation” is the meaningless repetition of two words that mean exactly the same thing.
For example, “human man” would be a nugatory expression. But “true being” or “being is true”
are not instances of just meaningless repetition, and so the true is not in every way the same as
being.
St. Thomas begins his response by noting that just as one attempts to reduce propositions
to self-evident principles—that is, one seeks demonstrations—so also in one’s investigation of
what something is, it is necessary to reduce or resolve what one knows to what is most known. But
according to Avicenna, that which the intellect first conceives as what is most known and that into
which it resolves all its conceptions is ens.73 As a consequence, all the other concepts of the
intellect are understood from addition to ens. But nothing extraneous to ens can be added to ens, in
the way in which a difference is added to a genus or an accident to a subject, since every nature is
essentially an ens: this is why Aristotle asserts in the Metaphysics that ens cannot be a genus.
St. Thomas explains that addition is made to ens, not as it were by adding something
extraneous to ens, which is impossible; but some things (that is, concepts or terms) said to add to
ens by expressing or signifying some mode of ens which is not expressed by the name ens. He
explains that this occurs in two ways.
73This priority is not in the order of time, but in the order of resolution. One should not take this claim about
the priority of the concept of ens as contradicting our earlier discussion of how being is known: ens is a
complex concept that presupposes the act of judgment, because the notion of ens is habens esse or id
quod est.
Again, if they were not in every way the same it would necessarily be the case that true adds
something beyond being; but the true adds nothing beyond being. . . .
On the contrary, the useless repetition of the same thing is nugatory (vain or meaningless); if
therefore true were the same as being, it would be nugatory when one says “true being,” which is
not the case; therefore they are not the same.
Carl: Metaphysics 86
Ways in which a concept or term can express something which ens does not express
(1) Categories: What the term or concept expresses is a certain special mode of being
(ens). St. Thomas explains that there are diverse grades of being (ens) according to which one
understands diverse modes of existing (esse), and under these modes are understood the diverse
genera of things: for example, substance (as a term or concept) does not add to being (ens) some
difference which designates a nature superadded to being (ens), but by the name of substance a
certain special mode of existing (esse) is expressed, namely ens per se, and the same goes for the
other categories. In this way, then, the ten categories (and all of the concepts that fall under each of
the ten categories) add to being, not by adding something extraneous to being, but by expressing
some mode of existing that is not explicitly expressed by the name being.
(2) Transcendentals: What the term or concept expresses is a general or common mode that
is consequent upon every being (ens). This occurs in two ways:
(a) First, according to what follows upon every being (ens) in itself.
And this occurs in two ways:
(i) First, the name or concept can affirmatively express the essence or that
according to which the thing is said to exist: in this way the name thing (res) is
THING imposed on being (ens). St. Thomas cites Avicenna, who holds that ens is taken
(RES) from the act of existing (actus essendi) whereas the name thing (res) expresses the
quiddity or essence of a being (ens).
(ii) Second, the name or concept can negatively express the lack of division that
ONE follows absolutely upon any being: insofar as something is a being, it is undivided.
(UNUM) The name that expresses this undivided character of being (ens) is one (unum). The
notion of one is undivided being.74
(b) Second, according to what follows upon a being (ens) in its relation to something else.
And this occurs in two ways:
(iii) First, insofar as every being (ens) is distinct from every other being, and in
SOMETHING this way the name something (aliquid) expresses, as it were, some other thing
(ALIQUID) (aliud quid). Whereas the name one expresses undivided being, the name
something expresses the distinction of this being from every other being.
(iv) Second, insofar as every being (ens) is related to the human soul. But there are
two powers of the human soul according to which beings are related to it:
Thus this kind of addition to being is divided into two ways:
(1) First, according to the relation to the appetitive power in the soul, being
GOOD insofar as it corresponds to the appetite is called good (bonum). This
(BONUM) follows Aristotle’s characterization of the good as what all things desire.75
(2) Second, according to the relation to the knowing power in the soul,
TRUE being insofar as it corresponds to a knowing power is called true (verum).
(VERUM) True thus adds to the notion of being (ens) the notion of conformity with
an intellect.
Thus, each of the transcendental terms (besides ens itself) adds something to the notion of
being that is not explicitly expressed by the term being (ens). This is not a matter of adding
something extraneous to being, but rather just expressing something not expressed by the term
being. For this reason, the transcendentals besides ens are not really distinct from ens, but are
distinct only according to reason. Thus, insofar as a being is a being, it is one, a thing, something,
74The origin of the doctrine of the transcendental character of one is Aristotle’s Metaphysics, in which he
emphasizes repeatedly that insofar as a being is, it is one.
75This is from the first line of the Nicomachean Ethics.
Carl: Metaphysics 87
good, and true.
10.3. The Order of the Transcendentals
In another text, DV 21.3, St. Thomas notes that there is an order among the
transcendentals, in that each of the transcendentals (besides ens) not only adds to being, but each
adds to being in a way that presupposes the previous transcendental:76
The term one presupposes being, because it adds to being the notion of indivisibility. True
adds to being the notion of relation to an intellect, but a thing’s intelligibility is a consequence of its
unity: and so the true adds to being in a way that presupposes unity. Similarly, the good
presupposes the true, in that whereas true adds to being the notion of a thing’s perfection as an
instance of a specific kind, good presupposes this, but also adds the notion of perfection in a thing’s
actual existence. That is, to name something true is to indicate its specific conformity with
intellect; to name it as good is to indicate the perfection that it possesses in its existence, in
accordance with which it is related to appetite as desirable.
This order among the transcendentals is important as a central issue in the discussion of
whether beauty is also a transcendental. In a number of texts, St. Thomas makes clear that beauty
adds something to good; but he never says that beauty adds to or is convertible with being. One
argument in favor of beauty’s transcendental character is to note that every transcendental
presupposes the former transcendental. Thus, if beauty adds something to good, it can also be said
to add something to being, just as good can be said to add something to true.77
76The translation is the Schmidt translation, available at www.dhspriory.org/thomas/QDdeVer21.htm.
77I have no settled view about whether beauty is a transcendental or whether St. Thomas thought of beauty as
a transcendental. although I lean towards a negative answer in both cases.
If the true and good are considered in themselves, then the true is prior in meaning to good since
the true perfects something specifically, whereas good perfects not only specifically but also
according to the existence which the thing has in reality. Thus the character of good includes more
notes than that of the true and is constituted by a sort of addition to the character of the true. Thus
good presupposes the true, but the true in turn presupposes the one, since the notion of the true is
fulfilled by an apprehension on the part of the intellect, and a thing is intelligible in so far as it is
one; for whoever does not understand a unit understands nothing, as the Philosopher says. The
order of these transcendent names, accordingly, if they are considered in themselves, is as follows:
after being comes the one, after the one comes the true; and then after the true comes good.
Carl: Metaphysics 88
10.4. Being and One in Aristotle’s Metaphysics
In In Meta. 4.2, St. Thomas introduces the Aristotelian discussion of being and unity by
observing that Aristotle’s purpose is to show that one and many, same and different are to be
studied by the first philosophy, just because to study these is to study being:
Hic procedit ad ostendendum quod ad
considerationem unius scientiae pertinent
considerare huiusmodi communia, scilicet unum et
multa, idem et diversum.
Here he proceeds to show that it pertains to the
consideration of one science to consider common
[things] of this kind, namely one and many, same
and different.
(I would emphasize that your translation of the Commentary on the Metaphysics
introduces the language of attributes to describe one and many, same and different in this text: St.
Thomas simply refers to them as communia, the common items.)
Throughout In Meta. 4.2, it is emphasized that being and unity are the same in reality but
differ in concept or ratio, following Aristotle’s remarks in Metaphysics 4.2 to this effect. In this
early book of the Metaphysics, Aristotle’s purpose is not to consider unity as such, but merely to
establish that it pertains to the metaphysician to consider unity, because unity and being are the
same in nature and differ only in concept.
We can summarize Aristotle’s claims in 4.2 and St. Thomas’s commentary as follows:
(1) Being and unity are the same in nature and differ only in concept. We find two
arguments in In Meta. 4.2 for this claim. The first is as follows:
Quod autem sint idem re, probat duabus rationibus,
quarum primam ponit ibi, idem enim, quae talis
est. Quaecumque duo addita uni nullam
diversitatem afferunt, sunt penitus idem: sed unum
et ens addita homini vel cuicumque alii nullam
diversitatem afferunt: ergo sunt penitus idem.
Minor patet: idem enim est dictum homo, et unus
homo. Et similiter est idem dictum, ens homo, vel
quod est homo: et non demonstratur aliquid
alterum cum secundum dictionem replicamus
dicendo, est ens homo, et homo, et unus homo.
But that they are the same in reality, he proves by
two arguments, the first of which he offers where
[he says] “For the same,” which [argument] is as
follows. Any two [things] which, added to one
[other thing], cause no difference, are entirely the
same: but and and being added to man or to any
other [thing] cause no difference: therefore they are
entirely the same. The minor is evident: for it is the
same to say man and one man. And similarly it is
the same to say man-being or that which is man:
and something else is not expressed when in
speaking we repeat in speech, it is a man-being,
Carl: Metaphysics 89
and a man, and one man.
Aristotle and St. Thomas’s point is that to call the same thing a man (homo), or one man
(unus homo), or a man being (ens homo) does not signify anything different in reality: whereas to
say “tall man” as opposed to “one man” does signify something different in reality. St. Thomas,
following Aristotle, goes on to note that this can also be seen by noting that whenever a man is
generated or corrupted, it is one man that is generated or corrupted. St. Thomas then clarify that
there is a distinction between being and one, but this is a conceptual distinction rather than a
distinction in reality.
The second argument is as follows:
Quaecumque duo praedicantur de substantia
alicuius rei per se et non per accidens, illa sunt
idem secundum rem: sed ita se habent unum et ens,
quod praedicantur per se et non secundum
accidens de substantia cuiuslibet rei. Substantia
enim cuiuslibet rei est unum per se et non
secundum accidens. Ens ergo et unum significant
idem secundum rem.
Any two things which are predicated of the
substance of some thing per se and not per
accidens, are the same in reality: but thus are one
and being, which are predicated per se and not
secundum accidens of the substance of each thing.
For the substance of each thing is one per se and
not secundum accidens. Therefore being and one
signify the same [thing] in reality.
St. Thomas goes on to explain that one is not predicated per accidens, because “a thing’s
substance is one and a being of itself and not by reason of something added to it.” That is, insofar
as a substance is, it is a being, and it is one. Being and one are not something belonging to a
substance by virtue of an accident—which is all that per accidens means here—but by virtue of the
substance itself.
(2) Nevertheless, these terms are not entirely synonymous. It is not nugatory to say “one
man.” Being and one do differ in concept, just not in reality.
(3) The unity that is the principle of number is not the same as the unity that is convertible
with being:
Unum igitur quod est principium numeri, aliud est
ab eo quod cum ente convertitur. Unum enim quod
cum ente convertitur, ipsum ens designat,
superaddens indivisionis rationem, quae, cum sit
negatio vel privatio, non ponit aliquam naturam
enti additam. Et sic in nullo differt ab ente
secundum rem, sed solum ratione. Nam negatio vel
privatio non est ens naturae, sed rationis, sicut
dictum est. Unum vero quod est principium numeri
The one therefore which is the principle of number
is different from that which is convertible with
being. For the one which is convertible with being,
designates being (ens) itself, adding the notion of
indivision, which, since it is a negation or
privation, does not posit some nature added to
being. And thus in no way does it differ from being
in reality, but only in ratio. For a negation or
privation is not a being of nature, but of reason, as
Carl: Metaphysics 90
addit supra substantiam, rationem mensurae, quae
est propria passio quantitatis, et primo invenitur in
unitate.
was said. But the one which is the principle of
number adds to substance the notion of measure,
which is the proper attribute of quantity, and is first
found in a unity [the unit].
(4) There are the same number of “parts” or “species” of unity as there are of being.
Sameness, equality, and likeness correspond to substance, quantity, quality:
Dicit ergo primo, quod ex quo unum et ens idem
significant, et eiusdem sunt species eaedem,
oportet quod tot sint species entis, quot sunt
species unius, et sibiinvicem respondentes. Sicut
enim partes entis sunt substantia, quantitas et
qualitas etc., ita et partes unius sunt idem, aequale
et simile. Idem enim unum in substantia est.
Aequale, unum in quantitate. Simile, unum in
qualitate Et secundum alias partes entis possent
sumi aliae partes unius, si essent nomina posita.
He says first therefore, that because one and being
signify the same [thing], and because of the same
[thing] the species are the same, it is necessary that
there be as many species of being as there are
species of unity, corresponding to one another. For
just as the parts of being are substance, quantity,
and quality, etc., so too the parts of one are same,
equal, and like. For “same” is one in substance.
“Equal” is one in quantity.” “Like,” one in quality.
And thus the other parts of one could be
understood according to the parts of being, if they
were given names.
(5) It can thus be concluded that it pertains to the metaphysician to consider unity along
with being:
Et sicut ad unam scientiam, scilicet ad
philosophiam, pertinet consideratio de omnibus
partibus entis, ita et de omnibus partibus unius,
scilicet eodem et simili et huiusmodi.
And just as the consideration of all the parts of
being pertains to one science, namely philosophy,
so too [the consideration] of all the parts of one,
namely sameness, likeness, and others of this kind.
Carl: Metaphysics 91
10.5. Truth as a Transcendental
As seen above, the true is included by St. Thomas in his list of transcendentals or
communissima. True is convertible with being, and it adds to being (ens) the relation of conformity
to an intellect. True expresses something not expressed by the term being, but it does not add
anything extrinsic or determining to being: every being is true, as a being.
Truth as a transcendental is often referred to by Thomists, therefore, as truth of being. This
truth of being can be distinguished from truth of intellect, which is the meaning of truth according
to which it is said that an intellect is true (or to be more precise, that an intellect’s judgment is true).
Truth of intellect and truth of being
It is primarily truth of intellect that is at issue in ST 1.16 aa. 1-2, where St. Thomas asks
whether truth resides only in the intellect and whether truth resides only in the intellect composing
and dividing. In light of the thesis that truth is a transcendental, it may at first be surprising that St.
Thomas claims that truth is only in the intellect and only in the intellect composing and dividing
(i.e., judging). On both of these points, as indicated by the two sed contra arguments, St. Thomas is
influenced by the teaching of Aristotle, according to whom (a) truth is in the intellect rather than in
things, and (b) there is truth in the intellect’s composing and dividing, but not in the knowledge of
what something is.
In the body of a. 1, St. Thomas gets at his point by contrasting the true with the good.
Whereas the good denotes that towards which appetite tends, the true denotes that towards which
intellect tends:
(1) The good is in the object desired, because appetite inclines the one who desires towards
the possession of the object of desire. The terminus of appetite is thus in the object desired. It is
therefore the goodness (or lack thereof) of an object desired that makes the appetite good (or not).
Good is in the object insofar as it is related to appetite, but it is the goodness of the object that
makes appetite good, not vice versa.
(2) By contrast, knowledge is the existence of the known (in some way) in the knower.
Knowledge or truth is therefore not in the thing known, but in the knower, insofar as the known
object exists in the intellect of the knower. Therefore the terminus of intellectual activity is not in
the thing known, but in the intellect. Thus, although the intellect is true insofar as it is conformed
to the thing understood, nevertheless the character of the true is primarily in the intellect and is in
the thing known by way of derivation. A being is called true insofar as it is related to some intellect
that knows it, but truth is first in the intellect and secondarily in the thing.
At this point, St. Thomas draws a distinction between two ways in which an object might
be related to an intellect. He notes that a thing understood (res intellecta) can be related to an
intellect either per se or per accidens.
(a) If a thing understood is related to an intellect that just happens to know it (or more
generally to an intellect by virtue of which it is something knowable—cognoscibilis), then this is
only a per accidens relation. That is, a given object can be knowable or actually known by a
human intellect, without in any way depending upon that intellect for its existence.
Carl: Metaphysics 92
(b) By contrast, a thing understood can be related to an intellect in such a way that the
thing depends upon that intellect for its existence or being (dependet secundum suum esse). In this
case, the relation to the intellect is per se, not per accidens. St. Thomas notes that this can occur
even with the human intellect: for example, a house depends upon the intellect of the architect. In
general, St. Thomas allows that artificial things are called true according to their relationship to the
intellect of the artisan.
But what we have called truth of being or transcendental truth is not by reference or
relation to the human intellect, because a given being’s relation to a human intellect is only per
accidens, not per se. However, all beings other than God are related to the divine mind as to that
upon which they depend for their very existence. Thus, “natural things are said to be true, insofar
as they possess a likeness of the species which are in the divine mind.” Truth is ultimately
primarily in the intellect, but in the divine intellect rather than the human intellect, because the
divine intellect is the principle upon which everything else depends for existence.
10.6. Additional Comments Concerning Good as Transcendental
As we have seen, good is also a transcendental term or notion. Another way in which this
thesis is expressed is the claim that being and good are convertible: that is, one can generally
replace any instance of ens in a proposition with bonum and preserve the truth of the proposition.
For example: the rock is a being the rock is good. If something exists or is a being, it can also
be said to be good.
This claim concerning the transcendental character of the good is foundational for
Thomistic ethical philosophy: what is good for a human being (or for anything else) is the
fulfillment or perfection of his (or its) being. To become good in the most complete way is to come
to be in the most complete way. St. Thomas spells this out nicely in ST 1.5.1, which asks whether
good differs from being (ens) in reality (secundum rem).
In the reply to the first objection in this text, St. Thomas adds a distinction concerning the
convertibility of being and good. Although being and good are the same in reality, nevertheless
because they differ from each other in thought, it is not the case that something is called being
simply (ens simpliciter) or good simply (bonum simpliciter) in the same way. Ens properly
expresses that something exists in act (ens dicat aliquid proprie esse in actu), and because act is
correlated to potency, a thing is called a being simply (ens simpliciter) insofar as it is distinguished
from that which is only in potency: thus ens simpliciter signifies a thing having substantial esse.
By contrast, any further actuality that a substance receives is not ens simpliciter (which is
its substantial being), but relative being or qualified being (ens secundum quid). That is, a
substance is further actualized by receiving accidents. For example, as St. Thomas notes, “to be
white” signifies relative or qualified existence (esse secundum quid), because “to be white” is not
the immediate actualization of what is in potency alone, because what is or becomes white must
possess substantial existence, esse simpliciter.
St. Thomas applies this distinction between ens simpliciter and ens secundum quid to the
notion of the good. St. Thomas notes that “good signifies the ratio of the perfect, which is
desirable.”78 Therefore, good simply (bonum simpliciter) signifies what is perfect, and what has its
78It is worth noting that this characterization of good as perfect being, which is desirable, adds something to
the account given in the text in the De veritate. For commentary on the importance of this development,
Carl: Metaphysics 93
ultimate perfection is said to be good simply; by contrast, what lacks the ultimate perfection that it
ought to have (although it has some perfection just insofar as it exists in act) is not said to be
perfect simply (perfectum simpliciter) or good simply (bonum simpliciter), but rather perfect and
good relatively or in a qualified way (secundum quid). Therefore, St. Thomas concludes that a
thing according to its primary esse (which is its substantial esse) is said to be ens simpliciter and
bonum secundum quid, insofar as it is a being (ens). But according to its ultimate actuality,
something is called ens secundum quid and bonum simpliciter.
These qualifications to the convertibility of being and good have at least two important
implications:
(1) First, this way of explaining the transcendental character of the good serves as the
appropriate metaphysical foundation for philosophical ethics. A human being’s ultimate perfection
and simple goodness is found not in its substantial being, but rather in the acquisition of further
actuality, of actuality that perfects human nature.
(2) Second, this qualification emphasizes that although being in general (ens commune)
and good in general (bonum in communi) are convertible, nevertheless in any finite being, being
simpliciter and good simpliciter are not identical. There is thus (as St. Thomas explains in q. 5 a. 4)
a relationship of final causality to the good simply in finite beings: every finite being is ordered to
the acquisition of its ultimate perfection and simple goodness, which are not identical with its
substantial being. As we will see later in our course, only in God are being simply and goodness
simply identical, because God is absolutely actual and perfect in Himself, without receiving any
actuality or perfection distinct from his esse.
see Rudi te Velde, “The Concept of the Good according to Thomas Aquinas,” Die Metaphysik und das
Gute, ed. Jan Aertsen, 79-104.
Carl: Metaphysics 94
11. How God is Known through Natural Reason
We now turn our attention from the study of the subject of metaphysics itself to
consideration of the first cause of being. We have already seen an indication of how the
examination of ens commune can lead to the assertion of the existence of God in the De ente et
essentia c. 4, where from the real composition of essence and esse in finite beings it is argued that
there must be a being whose esse is its essence, a subsistent esse that is the efficient cause of esse
in all other things that receive the actus essendi.
Curiously, St. Thomas does not employ this exact means of arguing for God’s existence
later in his career: that is, he does not set out to prove the existence of subsistent esse immediately
from the metaphysical structure of ens commune. One of the questions that we will address in our
consideration of natural theology is why St. Thomas later shows a preference, in practice, for other
ways of arguing for God’s existence.
11.1. Different Ways in Which God is Known
One of the first things that will need to be said concerning the knowledge of God
possessed by human beings in this life is that God’s existence is not strictly speaking self-evident.
In preparing to examine this topic, we should first note that St. Thomas carefully distinguishes
between different ways in which the existence of God can be known in this life.
The manner in which God’s existence is known to all
We turn first to a text from St. Thomas’s Lectura romana, d. 17 q. 1 a. 1.79 This text
distinguishes for us between different ways in which God can be known, in order to answer the
question of whether a supernatural light is necessary in order to love God. Because something is
loved only insofar as it is known, the ways in which God can be loved by human beings will
depend upon the various ways in which God can be known by human beings.
First, St. Thomas says that there is a knowledge of God that is possessed by all human
beings from the beginning of their lives, insofar as in knowing any created being there is a
knowledge of the creating God who creates that being. Because St. Thomas says that this is a
knowledge only of God’s effects, it seems that this knowledge of God is only implicit.
Corresponding to this kind of knowledge of God is a first way of loving God: insofar as one loves
a creature, one can be said to love God. This love, like the knowledge upon which it is founded,
seems to be implicit. St. Thomas says that both this knowledge and this love are possessed
naturally by all men. Insofar as any created thing is known or loved, in a sort of implicit way God
is known and loved, as the creating cause of these created things. In terms of what a human being
explicitly believes and loves, however, this implicit knowledge and love of God is consistent with
denying the existence of God and failing to explicitly love Him.
Second, St. Thomas says that there is a knowledge of God Himself, but from His effects.
This kind of knowledge occurs through the inquiry of reason, by which one proceeds from the
knowledge of effects to a knowledge of God. St. Thomas notes that this is the kind of knowledge
of God possessed by “the philosophers and other wise men,” who arrived at such a knowledge of
God through natural reason, insofar as it is possible to do so. Corresponding to this kind of
79The Lectura romana is St. Thomas’s incomplete secondary commentary on the Sentences. He began to
offer this commentary during his teaching in Rome, before abandoning the project to begin composition
of the Summa theologiae. The Lectura romana was lost almost immediately after the death of St.
Thomas, but a copy of it was found in the 20th century, and it was edited and finally published in 2006.
Carl: Metaphysics 95
knowledge of God is a love of God that is explicit and is founded upon this natural knowledge of
God through the inquiry of reason. We will comment more on this knowledge of God from His
effects shortly.
Third, there is the knowledge of God Himself that exceeds the proportion of any His
effects: such a knowledge goes beyond any knowledge that can be had concerning God by
reasoning from created effects. St. Thomas notes that this knowledge is not in men naturally; nor is
it acquired through the inquiry of reason; but it is infused through a supernatural light, i.e., through
the supernatural light of faith in this life and of the beatific vision given to the blessed.
Corresponding to this supernatural knowledge of God is a supernatural love of God, through which
one has a society or friendship with God. Such a knowledge and love are possible only by grace.
That every human being knows and loves God implicitly in the first way does not
contradict the fact that a given human being can fail to know and love God in the second and third
ways. The reason that this is a possibility is because, as St. Thomas explains, the existence of God
is not self-evident (per se notum) to us in this life.
St. Thomas also comments on the implicit and confused knowledge of God possessed by
all human beings in Summa theologiae I q. 2 a. 1 ad 1:80
11.2. That God’s Existence is not Self-evident to Us
St. Thomas addresses the question of whether God’s existence is self-evident a number of
times during his career. He takes as an advocate for the view that God’s existence is self-evident St.
Anselm of Canterbury, who famously proposed an argument for God’s existence that has, for better
or worse, come to be called the ontological argument.
St. Anselm’s argument
Although it is beyond our ability to examine this argument (in either of the two
formulations in which St. Anselm offers it) at this time, we can give a broad overview of the first
version of the argument and the reason that St. Thomas gives in criticizing it. According to first
formulation of St. Anselm’s argument, found in c. 2 of his Proslogion, the existence of God can be
known in an immediate way, just as soon as one recognizes that God is that greater than which
80All quotations from the Summa theologiae in this section of the notes are from the English Dominicans
translation, with occasional modification.
To know that God exists in a general and confused way is implanted in us by nature, inasmuch as
God is man’s beatitude. For man naturally desires happiness, and what is naturally desired by man
must be naturally known to him. This, however, is not to know absolutely that God exists; just as to
know that someone is approaching is not the same as to know that Peter is approaching, even
though it is Peter who is approaching; for many there are who imagine that man’s perfect good,
which is happiness, consists in riches, and others in pleasures, and others in something else.
Carl: Metaphysics 96
none can be thought. We will consider this argument according to how St. Thomas presents it in
Summa theologiae I q. 2 a. 1 obj. 2:81
St. Thomas’s presentation of St. Anselm’s argument is formulated in terms of the
Aristotelian understanding of self-evidence (notitia per se). A proposition is self-evident (per se
notum) when the proposition’s truth is evident just as soon as one understands the meaning of the
terms in the proposition. For example, the proposition “Every whole is greater than its part” is seen
to be true just as soon as one knows the meanings of the terms whole and part.
St. Thomas formulates the Anselmian argument for God’s existence in this way: as soon as
one knows that the word God signifies “that thing than which nothing greater can be conceived,”
he will at once see that God must exist, because for a thing to exist both in the mind and in reality
is greater than for it to exist only in the mind. That is, if one were to conceive of God as a being
existing only in the mind, this would contradict the claim that God is the greatest conceivable
being: and therefore God must exist.
St. Thomas criticizes the Anselmian argument in the following way:
81For Fr. Wippel’s comments on St. Thomas’s presentation and criticism of St. Anselm’s argument, see
Wippel 391-99.
Those things are said to be self-evident which are known as soon as the terms are known, which
the Philosopher says is true of the first principles of demonstration. Thus, when the nature of a
whole and of a part is known, it is at once recognized that every whole is greater than its part. But
as soon as the signification of the word “God” is understood, it is at once seen that God exists. For
by this word is signified that thing than which nothing greater can be conceived. But that which
exists actually and in the mind is greater than that which exists only in the mind. Therefore, since
as soon as the word “God” is understood it exists in the mind, it also follows that it exists actually.
Therefore the proposition “God exists” is self-evident.
Perhaps not everyone who hears this word “God” understands it to signify something than which
nothing greater can be thought, seeing that some have believed God to be a body. Yet, granted that
everyone understands that by this word “God” is signified something than which nothing greater
can be thought, nevertheless, it does not therefore follow that he understands that what the word
signifies exists actually, but only that it exists mentally. Nor can it be argued that it actually exists,
unless it be admitted that there actually exists something than which nothing greater can be
thought; and this precisely is not admitted by those who hold that God does not exist.
Carl: Metaphysics 97
First, St. Thomas notes that it is not evident to everyone that the name God signifies
“something than which nothing greater can be thought.” For example, some people have thought
that God—the highest being or the being guiding the universe—was a body; for example, the
Stoics thought of God as a body, even though they attribute intelligence and providence to God.
Granting for the sake of argument that everyone understands the signification of the name
God in the way that St. Anselm claims, still, it does not follow that what is signified by this word
exists actually, but only that it exists in the mind. In other words, St. Thomas will not allow that
one can reach an inference about the actual existence of God from the thought of a being greater
than which none can be thought, because it is not necessarily the case that anything exists in reality
that is the greatest conceivable thing. This is precisely what those who deny the existence of God
will deny: they deny that there is a correspondence between what is the greatest in reality and what
is the greatest conceivable thing; they deny that there is in reality something greater than which
nothing can be thought.
God’s existence is not self-evident to us
As St. Thomas explains in the body of Summa theologiae I q. 2 a. 1, something can be selfevident in two ways: (1) self-evident in itself, but not to us; (2) self-evident in itself, and to us. St.
Thomas reaffirms the Aristotelian notion of self-evidence a proposition is self-evident when the
proposition is known to be true as soon as the meaning of the terms in the proposition are known.
For example, “man is an animal” is seen to be true just as soon as one understands what a man is
and what an animal is. However, it should be noted that the meanings of these terms—man and
animal—are not immediately known to all. Even fewer will see the self-evidence of this
proposition: “Incorporeal substances are not in a place.”
St. Thomas then explains that the proposition “God exists” is self-evident in itself, because
God’s essence is His very esse, as is shown later in Summa theologiae I q. 3 a. 4. But God’s
existence is not self-evident to us, because His essence is not known by us in this life. These two
claims may seem to be in tension: that God’s essence is His esse, and that we do not know God’s
essence in this life. Although we can know the truth of the former proposition—we can know that
God’s essence is identical with His esse—nevertheless we do not know God’s essence in the way
that we know the essence of a man. That is, God’s esse in itself—God as He is in Himself—is not
known to us in this life. In this way the knowledge of God in this life is contrasted with the
knowledge of God promised to the blessed, that He will be seen face to face.
Therefore, St. Thomas concludes, it must be that God’s existence is known by us through a
demonstration from His effects. We turn now to a discussion of this topic.
11.3. How God’s Existence is Demonstrated
St. Thomas discusses how God’s existence can be demonstrated in the next article of the
Simma theologiae, I q. 2 a. 2. There, following Aristotle’s doctrine in the Posterior Analytics, he
explains that there are two kinds of demonstration:
(1) There is demonstration propter quid, in which one demonstrates something through its
cause, arguing from the cause to the effect. In this kind of demonstration, one’s reasoning process
parallels the very order of reality, insofar as a cause precedes its effect in reality (not always by a
temporal priority, but by a causal priority), one’s reasoning in a demonstration propter quid
Carl: Metaphysics 98
proceeds from what is prior in reality to what is posterior in reality. It is for this reason that one can
also call a demonstration propter quid a demonstration a priori. A demonstration propter quid
allows one to know not just that the conclusion is true, but also why it is the case. It should also be
noted that it is a requirement of demonstration propter quid that one’s knowledge of the cause be a
knowledge of the quiddity or essence of the cause: one has to know what the cause is in order to
demonstrate a truth concerning the effects of the cause.
(2) There is demonstration quia, in which one demonstrates only that something is the
case, by arguing from what is prior relative to us, i.e., effects. A demonstration quia presupposes no
knowledge of what the cause is, but instead establishes just that something is true concerning the
cause. In a demonstration quia, the order of one’s knowledge does not parallel the order of reality,
because in reality causes are prior to effects; whereas in a demonstration quia the knowledge of the
effect is prior to the knowledge of the cause.
Because God’s existence is not self-evident to us (which is because God’s essence is not
known to us in this life), St. Thomas asserts that God’s existence can only be known by us through
a demonstration quia rather than a demonstration propter quid. Indeed, it should be noted that no
demonstration propter quid concerning God’s existence is possible at all (even if one had
knowledge of the essence of God), because if one knew the essence of God, then His existence
would be self-evident. Furthermore, as will be shown later, God’s existence is not caused, and
therefore there can be no demonstration from a cause to God’s existence understood as an effect.
Every argument for God’s existence will therefore proceed from a knowledge of certain
created realities, which will come to be recognized as effects that can only be caused by the being
that we call God. We will see St. Thomas’s procedure in constructing such arguments when we turn
to consideration of his ways of proving God’s existence in Summa theologiae I q. 2 a. 3.
11.4. The Impossibility of Quidditative Knowledge of God
Before proceeding to a consideration of argumentation for God’s existence, we should
consider a claim that has already been made—that in this life we cannot know what God is—but
which has not been directly defended. Indeed, in the texts of the Summa theologiae that we have
examined so far, St. Thomas takes it for granted that in this life a quidditative knowledge of God
(that is, a knowledge of what God is) is impossible. In other contexts, however, he explains why it
is that such knowledge of God is impossible in this life.
The meaning of quidditative knowledge
To begin, we should clarify what we mean when we say that quidditative knowledge of
God is impossible for human beings in this life. By this, we mean that a human being cannot know
what God is, in the technical sense in which one knows what something is by knowing its essence.
For example, to know what man is is to know that man is a rational animal with flesh and bones,
etc. If one knows that man is risible, or musical; or if one knows that this man is tall, or white—all
of these instances of knowledge about man fall short of a quidditative knowledge of what man is
essentially. When we deny that we are capable in this life of knowing what God is, we mean that
we cannot possess a knowledge of God’s essence like the knowledge of the essence of a man
expressed by the definition of man.
Why quidditative knowledge of God is impossible in this life
Quidditative knowledge of God, in this strict and technical sense, is impossible in this life.
In In DT 1.2, St. Thomas offers an explanation as to why this is the case. He begins by offering a
division of the ways in which a thing can be known:
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(1) A thing can be known through its proper form, as when the eye sees a stone through the
species of a stone.
And this in two ways:
(a) Through the very form of the thing itself, as God knows Himself and an angel
knows itself. (That is, the self-knowledge of God and of the angels is not in any
way mediated by any form other than their own essences.)
(b) Through a form which is other than the thing known.
Either:
(i) When the form has been abstracted from the thing, as how the human
intellect knows the essence of something such as a stone
(ii) When the form is impressed on the intellect by a thing, which is how
an immaterial thing would be known in a direct way by the human
intellect.
(2) A thing can be known through some other form that is similar to the thing, as when a
cause is known through its effect; for example, as a man is known through the form of an image in
a mirror.
And this in two ways, according to two kinds of effects:
(a) There are effects adequate to the power of the cause, and through such an effect
the power of the cause can be fully known, and consequently the essence of the
cause.
(b) There are effects that are not fully equal to their cause, and through such an
effect neither the power nor the essence of the cause can be comprehended; instead
it can only be known that the cause exists.
Based upon this division of the ways in which a thing can be known—that is, of the
various forms through which a thing can be known—St. Thomas proceeds to explain why the
quiddity of God cannot be known in this life through any of the ways outlined above. He first
explains that because the human intellect, in the present life, has a determined relation to forms
abstracted from sensible things—because human understanding depends upon phantasms present
in the imagination, which are derived from sense experience—it cannot be the case that we would
know God through His very essence in this life, because God is immaterial and therefore cannot be
sensed. We know the essence of a stone by abstracting a form that is a likeness of the essence of a
stone from a phantasm of the stone, which is derived from our sense experience of the stone. No
such sense experience is possible concerning God, and so it cannot be the case that we could know
God through His essence in this life.
By this explanation, St. Thomas has excluded both (1-a) and (1-b-i) from the division
above: God is not known through His very essence in this life (because this cannot be known
through the senses), and He is not known immediately through any form abstracted from matter.
However, it is the case that the blessed in heaven, who enjoy the beatific vision, know God through
His very essence, the way identified as (1-a) above. But no one can ever know the essence of God
in the way identified as (1-b-i).
Next, St. Thomas excludes the possibility that God’s essence could be known, in this life,
by any form impressed by God upon the human intellect, by noting that God infinitely transcends
every created form (a form distinct from His own essence and impressed on the mind would be a
created form). Therefore, it cannot be the case that God would be made known in His essence even
through a form supernaturally impressed on our intellect in this life. St. Thomas also excludes the
possibility that a form that is a likeness of an angel (a pure intelligence) could make God’s essence
Carl: Metaphysics 100
known to us, because the human intellect is naturally proportioned (or connaturally related) to
knowing through phantasms.
At this point, St. Thomas has excluded every kind of proper form through which a thing
can be known with regard to knowledge of the essence of God: in this life we cannot see the
essence of God itself; we cannot abstract a form from sense experience through which we would
know the essence of God; and we cannot know the essence of God even by any form impressed on
our intellect, whether by God or by angels. What this leaves, then, is only the possibility identified
as (2) above, that God can be known through His effects.
But because no created effect is equal to God, it cannot be the case that God’s power can
be comprehended from a knowledge of created effects. Without a comprehensive understanding of
the power of God as the cause, His essence will remain unknown to us, even though we can know
from such effects that He exists.
Thus, the impossibility of quidditative knowledge can be explained from two theses, one
concerning the manner in which human beings know in this life, and the other concerning the
comparison of creatures to God:
(1) All human knowledge in this life (except that resulting from forms impressed on the
mind by God or angels) is derived from sense experience, because the human intellect is naturally
proportioned and connaturally related to knowledge through phantasms, which are produced in the
imagination as the fruit of sense experience. It is for this reason that St. Thomas will often say that
the natural object of the human intellect is the quiddity of corporeal substances, because these are
the things that can be known through the senses.
(2) Every effect falls short of the infinite perfection of God, because God cannot create
another God. Every creature is finite, and thus no knowledge of God from created effects can ever
lead one to a knowledge of what God is in Himself. Even as regards that knowledge resulting from
forms impressed on the mind by God or angels, such forms cannot result in a knowledge of what
the divine essence is, because these forms are also created forms that fall short of their divine
cause. The only way that God can be known in His essence is through the beatific vision of that
essence in the life to come.
Concluding remarks
We have now explained why St. Thomas denies the possibility that God’s essence can be
known in this life, and as we have seen, this claim is presupposed in his argumentation for (1) the
claim that God’s existence is not self-evident and (2) the claim that God’s existence can only be
demonstrated from created effects. Now that we have some understanding of how St. Thomas
thinks the existence of God can be demonstrated, we will proceed to a consideration of his first
way of arguing for God’s existence.
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12. Argumentation for God’s Existence: the First Way
In Summa theologiae q. 2 a. 3, St. Thomas famously proposes five ways in which the
existence of God can be proved. In general, what the five ways share in common is that each of
them proceeds from some feature of reality, arguing that this feature must be the effect of a cause
that we understand to be God. The five ways thus argue from the following features of reality:
First way from motion
Second way from the nature of efficient causality
Third way from possibility and necessity in things
Fourth way from the gradation found in things
Fifth way from the governance of the world
12.1. The First Way: Argument from Motion
We will begin by offering a brief commentary on the text of the first way. Our treatment of
this argument will be somewhat cursory, serving more to highlight the questions that need to be
investigated concerning it, rather than answering all such questions.
The first way begins by noting a particular feature of the world that is evident to the
senses: the fact of motion, that some things are in motion.
The first and more manifest way is the argument from motion. It is certain, and evident to our
senses, that in the word some things are in motion.
Now whatever is in motion is moved by another, for nothing is in motion except insofar as it is in
potency to that to which it is in motion; whereas a thing moves [something else] inasmuch as it
(the mover) is in act. For to move [something] is nothing other than to educe something from
potency to act. But something cannot be reduced from potency to act, except by some being in act:
as fire makes wood, which is potentially hot, to be actually hot, and through this it moves and
alters it. But it is not possible that the same thing should be at the same time in act and in potency
in the same way, but only in different ways: for what is actually hot, cannot at the same time be
potentially hot, but it is at that same time potentially cold. It is therefore impossible that, in the
same respect and in the same way, something should be both mover and moved, or that it should
move itself. Therefore whatever is in motion must be moved by another.
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The longest portion of the text of the first way is devoted to a defense of this claim:
whatever is in motion is moved by another (omne quod movetur ab alio movetur). This thesis is
taken by St. Thomas from Aristotle’s Physics and Metaphysics, where Aristotle devotes
considerable attention to proving this claim.82 In the Latin, the repetition of the passive form
movetur could appear to render the principle tautological. However, based upon the meaning that
this principle has in the Physics and Metaphysics, and given the defense that St. Thomas offers of
the principle here, it is better rendered as “whatever is in motion is moved by another.”
The defense that St. Thomas offers of this principle (sometimes called the motor causality
principle) here depends upon an analysis of the relationship between potency and act. Motion is
defined here as the eduction of act from potency, or the reduction of potency to act.83 But
something in potency is only brought into act by something already in act: this is a general
observation about the relationship between act and potency, that the actualization of potency
requires that what actualizes already be in act. Consistent with this observation, we have seen in
every case of act-potency composition that St. Thomas urges the necessity of identifying a cause in
act responsible for the act principle.84
The question to be raised, then, is whether or not a given thing could be capable of
reducing itself from potency to act, i.e., of moving itself. St. Thomas explains that this is not
possible, because a thing cannot be in potency and in act in the same respect at the same time. He
explains this by way of example: what is only potentially hot cannot be the cause of the acquisition
of heat. For a thing to be its own first mover would require that a thing both be and not be at the
same time and in the same respect, and so it can be concluded that whatever is in motion is moved
by another.
So far, St. Thomas has argued for two claims:
(1) Certain things in the world are in motion.
(2) Whatever is in motion is moved by another.
82Indeed, within the Physics, the demonstration of the principle omne quod movetur ab alio movetur
represents the culmination of natural philosophy, as this is the final demonstration propter quid in the
Physics.
83It is important to note that this is a more general definition of motion than the definition of motion found in
the Physics.
84Insofar as the principle omne quod movetur ab alio movetur is concerned with motion, defined here as “the
reduction of potency to act,” a question to be asked is whether every instance of act-potency composition
will fall under the principle. The point I am making above is just that in every case of act-potency
composition, something actual is the cause of the act-principle in the composite.
If that by which it is put in motion be itself put in motion, then this also must be put in motion by
another, and that by another again. But this cannot go on to infinity, because then there would be
no first mover, and, consequently, no other mover; seeing that subsequent movers move only
inasmuch as they are put in motion by a first mover; as the staff moves only because it is put in
motion by the hand. Therefore it is necessary to arrive at a first mover, put in motion by no other;
and this everyone understands to be God.
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Now St. Thomas offers and defends a third claim:
(3) It is impossible to proceed to infinity in moved movers.
And then he draws his conclusion:
(4) There is some first mover that is not put in motion by anything else—and everyone
understands this to be God.
Concerning the argumentation against an infinite regress of moved movers, it is sometimes
objected that the argument seems to engage in a begging of the question, by its insistence that the
absence of a first mover is problematic. Such an objection misses that this claim is immediately
defended by St. Thomas, through this principle: subsequent movers act as movers only inasmuch
as they are moved by a first mover. To be a subsequent mover—a moved mover—is always to
depend upon a first mover in the sequence of movers. This principle does not presuppose the
conclusion of the first way, because that conclusion is that there must be a first mover, put in
motion by no other. In the example that St. Thomas uses to defend this principle, he is willing to
speak of the hand as a “first mover,” relative to the staff, but he would not say that the hand is put
in motion by no other.
Another way to put this principle then, is just this: a subsequent moved mover depends
more upon a remote mover than upon its own proximate mover for its being moved. It is the prior
mover (and ultimately the first mover) that accounts for the motion of all subsequent movers. To
deny an ultimate prior mover is therefore to deny motion in any of the subsequent movers in the
series.
Difficulties about the argument
(1) The first way suggests that a general question to be asked concerning anything that one
identifies as the first mover of a sequence of moved movers is this: is this mover put in motion by
another? Is there in it the actualization of some potency that requires the agency of a prior mover?
It is by an affirmative answer to these questions that one would be led to posit a first mover, put in
motion by no other, and it is this mover alone that St. Thomas calls God. What is not spelled out, in
the text of the first way, is an attempt at an exhaustive classification of the kinds of movers, so as
to get at the truth of the claim that it in every case the agency of a given mover that isn’t a totally
unmoved mover requires that there be a totally unmoved mover that we understand to be God.
One can respond to this objection by noting that the argument is expressed in such general
terms—with reference to act and potency—that such descent to particular details is unnecessary.
By framing the argument in terms of act and potency, what St. Thomas’s conclusion serves to
establish is the existence of something in act that is not dependent upon anything else for its being
in act.
(2) Another difficulty is that it does not seem to be obvious that a first mover, put in
motion by no other, must be God. This difficulty dovetails with the first, insofar as one might think
that even an unmoved first mover could be, e.g., a soul or a formal cause.
To the degree that one finds this objection compelling, one can regard the conclusion of the
first way—“and this everyone understands to be God”—as a sort of promissory note rather than a
demonstrated conclusion. That is, a first mover put in motion by no other might not obviously be
God, but subsequent argumentation about the characteristics of the first mover will include
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characteristics understood to be exclusive and proper to God alone: absolute simplicity, perfection,
infinity, eternity, etc. If it seems too hasty to assert that a first mover must be God, then this is a
difficulty only to be settled by subsequent argumentation. Nevertheless, in looking back upon the
first way (after that subsequent argumentation), one could then recognize that it was God’s
existence that was demonstrated.
Is this an argument in physics or metaphysics?
Owing to the fact that the first way is an argument from the fact that there are beings in
motion, no small number of commentators have thought that the first way must therefore belong
properly to physics (the subject of which is mobile being) rather than to metaphysics. Against such
a suggestion, I would note two things: (1) The meaning of motus in the principle omne quod
movetur ab alio movetur is exceptionally broad for St. Thomas, as evidenced by the fact that later
in the Summa theologiae, he includes the operations of the human will as falling under the
principle (and he references the first way for proof of this principle). (2) Unlike other ways of
arguing for the principle omne quod movetur ab alio movetur which are properly physical (and
which St. Thomas does employ in his presentation of the argument from motion in the Summa
contra Gentiles), by relying upon an analysis of the relationship between act and potency, St.
Thomas argues for this principle in particular in a manner more appropriate to metaphysics than to
physics: as we have noted before, act and potency themselves belong to the subject-matter of
metaphysics, as two of the features attending ens commune.
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13. Divine Simplicity: God as Ipsum Esse
Following the demonstration of God’s existence, St. Thomas proceeds to a consideration of
what other truths can be known concerning God besides the fact of His existence. The first truths
that St. Thomas demonstrates concerning God, both in the Summa contra Gentiles and in the
Summa theologiae, fall under the heading of what is called the divine simplicity, that is, the denial
of any composition in God.
13.1. How Truths Beyond God’s Existence Can Be Known: the Via Remotionis
As affirmed above, St. Thomas denies the possibility of any quidditative knowledge of
God in this life: it is impossible for human being’s to know the essence of God, to know what God
is in Himself, in this life. As St. Thomas has explained, from God’s effects one can only know that
He exists, not what He is.
If this were the last thing to be said concerning the knowledge of God possible according
to natural reason, then we would face the difficulty that one could not argue from natural reason
against someone who, for example, denied that God is one, that God is intelligent, that God is
powerful, that God is loving, etc. As we will shall see, St. Thomas does consider such truths to be
demonstrable by natural reason (that is, by reason not directly aided by revelation). We should
comment now on how St. Thomas thinks that this can be the case.
The via remotionis
In Summa contra Gentiles I c. 14, St. Thomas notes that, by the end of c. 13, the existence
of God as the First Being has been established. Having established the existence of God, it is now
appropriate to investigate His properties or conditions (eius conditiones). St. Thomas then asserts
that in order to accomplish this, it will be most appropriate to make use of the way of remotion (via
remotionis), also sometimes called the via negativa or negative way.
That in this life we cannot know what God is does not mean that we are unable to know
what God is not. Indeed, knowing what God is not is extremely valuable as a way of knowing Him.
St. Thomas explains:
Now, in considering the divine substance, we should especially make use of the method of
remotion. For, by its immensity, the divine substance surpasses every form that our intellect
reaches. Thus we are unable to apprehend it by knowing what it is. Yet we are able to have some
knowledge of it by knowing what it is not.
Furthermore, we approach nearer to a knowledge of God according as through our intellect we are
able to remove more and more things from Him. For we know each thing more perfectly the more
fully we see its differences from other things; for each thing has within itself its own being, distinct
from all other things. So, too, in the case of the things whose definitions we know. We locate them
in a genus, through which we know in a general way what they are. Then we add differences to
each thing, by which it may be distinguished from other things. In this way, a complete knowledge
of a substance is built up.
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Although we are not capable of knowing what God is, nevertheless we are capable of
distinguishing God from other things by noting the things that God is not. Indeed, as we indicated
at the beginning of our course, even the positive knowledge of an essence or quiddity always also
involves coming to know the thing in question as distinct from all other things: this is why even the
positive knowledge of the essence of a corporeal substance is expressed through a genus and
difference, in which the thing is divided from every other member of the genus.85 One thus grasps
only in a general way what a thing is, and then proceeds to differentiate it from other members of
its genus.
In other words, there is a negative element even in the quidditative knowledge of a finite
substance. Therefore, it should not be a surprise that even though quidditative knowledge is not
possible concerning God, nevertheless a broadly similar negative knowledge—a knowledge of
what God is not—will still be possible. However, St. Thomas adds some important qualifications
concerning this negative approach to knowledge of God:
St. Thomas notes that unlike the knowledge of the quiddity of a corporeal substance, we
cannot begin our examination of God by placing Him in any genus: even the statement of a thing’s
genus is already a grasp of what the thing is. Nor will we distinguish God from other things by
affirming a difference: every difference is a positive characteristic (e.g., rationality). A difference
serves to distinguish a quiddity from other quiddities in the same genus, but it does so insofar as it
is a positive characteristic possessed by the quiddity. A difference adds to the genus, and this is
why it must be taken from outside the genus.
85We cited the following text from SCG 3.46: “But through knowing about a thing what it is, the thing is
known just as it is distinct from other things: therefore also a definition, which signifies what a thing is,
distinguishes the definitum from all other things.”
However, in the consideration of the divine substance we cannot take a what as a genus; nor can
we derive the distinction of God from things by differences affirmed of God.
For this reason, we must derive the distinction of God from other beings by means of negative
differences. And just as among affirmative differences one contracts the other, so one negative
difference is contracted by another that makes it to differ from many beings. For example, if we
say that God is not an accident, we thereby distinguish Him from all accidents. Then, if we add that
He is not a body, we shall further distinguish Him from certain substances. And thus, proceeding in
order, by such negations God will be distinguished from all that He is not. Finally, there will then
be a proper consideration of God’s substance when He will be known as distinct from all things.
Yet, this knowledge will not be perfect, since it will not tell us what God is in Himself.
Carl: Metaphysics 107
Therefore, one does not distinguish God from other beings by affirmative differences, but
by negative differences. St. Thomas then compares affirmative differences and negative
differences, by first noting that affirmative differences contract one another: for example,
corporeality (the difference of body as a species of substance) is itself further contracted by life
(the difference of living things), which is in turn further contracted by sensitivity (the difference of
animal), which is further contracted by rationality (the difference of man). Negative differences, in
a similar fashion, can serve to distinguish a thing from more and more things; in this way negative
differences too contract one another, as the thing being distinguished by negative differences has
more and more things removed from it. It is for this reason that the procedure of knowing God
through such negative differences is called the way of remotion: one removes from God all those
things that He is not, so as to come to a proper consideration of God’s substance as distinct from all
things. Nevertheless, this proper consideration of God as distinct from all things (ut ab omnibus
distinctus) is not a knowledge of what God is in Himself.
St. Thomas concludes SCG I c. 14 by announcing that he will take what was established in
the argument from motion as a starting point in the way of remotion: this is the proposition that
God is absolutely unmoved. As the order of the divine attributes unfolds in the Summa contra
Gentiles, everything said about God ultimately depends upon this claim that God is unmoved in
every way.
The Summa theologiae on how God’s attributes are known
The text in the Summa theologiae that parallels Summa contra Gentiles I c. 14 differs
somewhat in emphasis, and it is worth it to examine this text briefly before proceeding to our
examination of St. Thomas’s actual arguments for the divine attributes. This parallel text is Summa
theologiae q. 3 pr.:
It being known of something whether it is, it remains to be inquired how it is, so that it may be
known about it what it is. But since of God we cannot know what He is, but [only] what He is not,
we cannot consider about God how He is, but rather how He is not. First therefore how He is not
will be considered; second how He may be known by us; third, how He may be named.
But it can be shown about God how He is not, by removing from Him those things which do not
belong to Him, such as composition, motion, and others of this kind. First therefore we will inquire
about His simplicity, through which composition is removed from Him. . .
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Whereas the text from the Summa contra Gentiles emphasizes that by the way of remotion
we remove from God what He is not, in this text from the Summa theologiae instead St. Thomas
says that we remove those things that concern how He is not. What does St. Thomas mean by how
(quomodo) something is, as distinguished from what (quid) it is? Given what he says here, it would
seem that quomodo sit is the question that is asked concerning a subject of study, once its existence
has been shown but before its quiddity is known: that is, answering the question quomodo sit is
what a science does in the stage in between knowing whether its subject exists (an sit) and its
reaching conclusions about the definition of its subject (quid sit). This suggestions seems to be
confirmed by a brief text from the Commentary on the Physics, in which St. Thomas notes that “it
pertains to natural [philosophy] to determine about the infinite, if it is or if it is not, and how it is,
and what it is. . .”86 Here the question quomodo sit is inserted in between the questions an sit and
quid sit.
When St. Thomas says, therefore, that we cannot know how God is, because we cannot
know what He is, he means that it is the knowledge of how something is—its mode of being—that
allows one to arrive at knowledge of what it is (and thus how it is positively distinguished from all
other things). Because we cannot know what God is, therefore neither can we know how God is.
Therefore, instead of saying what God is not, St. Thomas proceeds in the Summa theologiae by
explaining how God is not, that is, by removing those modes of being that are unfitting. This
begins with the removal of every mode of composition, i.e., the assertion of the divine simplicity,
to which we now turn.
13.2. Establishing Divine Simplicity
St. Thomas treats the divine simplicity in detail in both Summa contra Gentiles I cc. 16-27
and in Summa theologiae I q. 3. We will base the following discussion on the latter texts, and we
will summarize many of St. Thomas’s arguments.
a. 1: God is not a body
St. Thomas begins by removing from God the corporeal mode of existence, arguing that
God cannot be a body because:
(1) No body is a mover unless it is itself in motion.87 But God is an unmoved mover.
Therefore, God is not a body.
-This argument depends upon a thesis taken from Aristotle’s Physics, that whenever a body
is a mover it must also be something in motion.
(2) The first being must be in act and in no way in potency, since act absolutely precedes
potency (because whatever is in potency is reduced to act only by some being in act). But God is
the first being. Therefore God is without any potency and is pure act. But every body is in potency
to something. Therefore God is not a body.
-Although St. Thomas’s announced purpose is just to argue that God is not a body, he
accomplishes this by arguing for something more radical and fundamental, that God is pure act
with absolutely no potency. This claim will have important implications as St. Thomas’s arguments
concerning the divine attributes unfold.
86In Libros Physicorum Bk. 4, lec. 1.
87St. Thomas says that this is clear by induction through singulars. It is also a thesis asserted by Aristotle in
Book III of the Physics.
Carl: Metaphysics 109
a. 2: God is not composed of matter and form
At issue in a. 2 is the question of whether or not God might be composed of matter and
form, despite the fact that He is not a body. This might seem to be an unnecessary question, but no
small number of medieval theologians thought that some incorporeal realities—angels—are
composed of matter and form: not corporeal matter, but spiritual matter.
St. Thomas argues elsewhere (such as in the De ente et essentia) against such a view, by
observing that corporeal matter is not of itself intelligible to the human intellect: it is form that is
the principle of intelligibility, because everything is known according to formal likeness. If one
distinguishes prime matter as a genus into corporeal matter and spiritual matter, then one must say
that the substantial form that makes corporeal matter to be corporeal matter is itself the principle of
the unintelligibility of corporeal mattter: but it is absurd to suggest that a form could be a principle
of unintelligibility.
Concerning whether or not God could be a composite of matter and form, St. Thomas
argues in q. 3 a. 2 that this is impossible, because God is pure act, whereas matter is a principle of
potency. The main argument establishing the lack of matter-form composition in God in a. 2 is
therefore what was demonstrated in a. 1, that God is pure act with absolutely no potency.
a. 3: God is the same as His essence
In corporeal substances, which are individual instances of universal essential kinds, there
is always a distinction between the individual and its essence. That is, Socrates is a man, but he is
not humanity. The question considered in a. 3 is whether there is a similar distinction to be drawn
between God and His essence?
St. Thomas answers this question by explaining that in corporeal substances, the reason for
the distinction between the individual (suppositum) and its essence is the matter-form composition
of these substances. Humanity and a man are not absolutely identical, because the man has
particular matter that is not included in the abstract essence, humanity. Because in any incorporeal
substance there is no matter-form composition, St. Thomas argues that suppositum and essence or
nature will be identical. He concludes: “And thus, since God is not composed of matter and form,
as was shown, it must be that God is His deity, His life, and whatever else is thus predicated of
Him.” It should be noted that this conclusion—the identity of suppositum and essence—applies
also to angels.88
a. 4: in God essence and esse are identical
We now proceed to a consideration of one of the most famous texts of the Summa
theologiae: I q. 3 a. 4, in which St. Thomas argues for the identity of essence and esse in God. He
offers three arguments for this conclusion; we will consider the first two, leaving aside the third
because of its dependence upon the notion of participation, which we have not treated in this
course.
(1) Whatever a thing has besides its essence must be caused either by the principles of that
essence (e.g., in the way that properties are caused by essence) or by some exterior agent (as heat is
caused in water by fire). Therefore if a thing’s esse differs from its essence, then this esse must be
caused, either by some extrinsic agent or by the essence of the thing. It is impossible, however, for
anything’s esse to be caused by its essence, because in such a case a thing would be the sufficient
cause of its own existence, which is absurd. Therefore, anything whose essence differs from its
88However, there is some controversy about whether St. Thomas later changed his mind about this claim as it
applies to angels. See Wippel 243-53.
Carl: Metaphysics 110
esse must have its esse caused by an extrinsic agent. But this cannot be true of God, because God is
the first efficient cause.
-If essence and esse are distinct in any given thing, then the esse must be caused, either by
the essence or by an extrinsic agent; but it is impossible for a thing’s essence to be the cause of its
own esse, because then the thing would be a sufficient self-cause with regard to its existence,
which cannot be admitted. Therefore God’s essence cannot be the cause of His esse. This leaves
only the possibility that God’s esse is caused by some other agent. But God is the first efficient
cause and is totally uncaused—this was established by St. Thomas in his second way of arguing for
God’s existence. Therefore, in God, essence and esse must be identical.
(2) Esse is the actuality of every form or nature: for example, goodness and humanity are
not signified in act, except insofar as we signify them to be (esse). Therefore esse must be
compared to essence, if the latter is distinct from the former, as act to potency. But in God there is
no potency, because He is pure act, and so in Him esse and essence cannot differ.
-Once again we find that the claim that God is pure act is used to establish a further claim
about the divine simplicity. Because essence-esse composition is an instance of potency-act
composition, it cannot be the case that in God there is a composition of essence and esse, and
therefore in Him essence and esse are the same.
a. 5: God is not in a genus
Having established the identity of essence and esse in God, St. Thomas proceeds in a. 5 to
argue that God is not in a genus. St. Thomas begins by distinguishing between two different ways
in which a thing can be said to be in a genus:
(a) by being contained under that genus as a species
(b) by being the principle of the genus (e.g., this is how a point is in the genus of
continuous quantity, by being the principle of extension, even though a point is not itself something
having extension) –we will leave behind specific commentary on St. Thomas’s brief argument
against this possibility
Regarding the first possibility, being contained under a genus as a species, St. Thomas
offers three arguments:
(1) Every species in a genus is constituted by the genus plus a difference. By this
composition, the relationship of the difference to the genus is a relationship of act to potency. But
God is pure act without potency, and so He cannot be contained in a genus as a species.
(2) In God essence and esse are identical. If therefore He were in a genus, His genus would
have to be ens, since the genus signifies the essence of a thing. But ens cannot be a genus, for the
reasons given by Aristotle. Therefore God is not in a genus.
(3) Everything in a given genus agrees or shares in the essence of the genus that is
predicated of them to express what they are. However, these things sharing a genus also differ in
esse from one another. Therefore in every member of a genus, esse and quiddity or essence must
differ.89 But in God essence and esse do not differ. Therefore God is not in a genus as a species.
That God is not contained in a genus has two important implications: (1) It is absolutely
impossible to offer a definition of God, because a definition is given by naming the genus and
specific difference of a thing. (2) God shares nothing in common univocally with any creature,
because every creature is in a genus. We will comment more on this latter claim later, in our
89This is an instance of what is typically called the genus argument for real distinction of essence and esse.
Carl: Metaphysics 111
discussion of the “transcendental” analogy between God and creatures.
a. 6: in God there are no accidents
Next, in a. 6, St. Thomas argues that there is no substance-accident composition in God.
We will briefly note only his first argument:
(1) A subject of accidents is related to its accidents by a relationship of potency to act. But
God is pure act without potency, and therefore He cannot have any accidents.
-Again, we find St. Thomas arguing for a kind of simplicity in God from His being pure
act without potency. There can be no substance-accident composition in God because God is pure
act.
a. 7: God is simple in every way (omnino simplex)
Summarizing and generalizing the conclusions reached in q. 3, in a. 7 St. Thomas
concludes that God is in every way simple. His first argument for this conclusion is just from the
previous articles of q. 3: he summarizes the various modes of composition or complexity that have
been excluded from God.
(1) God has no composition of quantitative parts, because He is not a body.
(2) God has no matter-form composition.
(3) There is in God no distinction between nature and suppositum.
(4) God has no essence-esse composition.
(5) God has no composition of genus and difference.
(6) God has no subject-accident composition.
St. Thomas concludes from this list that God is in every way simple. The form of argument
employed here is induction, which is valid so long as St. Thomas has provided an exhaustive or
complete list of the possible ways in which a thing can be composite. These are indeed all of the
modes of composition found in beings under ens commune, and so St. Thomas’s argument is valid.
St. Thomas then adds several other arguments for the absolute simplicity of God, which we
need not consider at this time.
a. 8: God does not enter into composition with other things
So far, it has been established that there is no composition in God himself: He is absolutely
simple, with none of the modes of composition found in creatures present in Him. But it could be
suggested that even though God is not Himself composite, perhaps He enters into composition with
other things: just as a substantial form is in itself something simple, but it nevertheless enters into
composition with prime matter.
St. Thomas notes that there have been three erroneous views connected with this
suggestion:
(a) That God is the world-soul or the soul of the outermost heavenly sphere.
(b) That God is the formal principles of all things
(c) That God is prime matter, which was “most foolishly” posited by David of Dinant.
St. Thomas then offers three arguments against any such view that God is composite with
other things. We will note only the first, which proceeds from the claim that God is an efficient
cause.
(1) Because God is the first efficient cause (as was established by the second way), He is
not the intrinsic formal cause of anything that He causes: for an efficient cause can only of the
same form specifically as the form that it causes, not numerically. Furthermore, because He is the
first efficient cause, He cannot be prime matter, which is pure potency.
Carl: Metaphysics 112
Final comments on divine simplicity
We have carefully attended to the contents of Summa theologiae I q. 3 concerning the
divine simplicity. It is important to emphasize that in itself the doctrine of divine simplicity is that
in God there is not any kind of composition whatsoever. This doctrine can be “broken down,” as it
were, according to the various kinds of composition that are found in finite beings but not in God.
It is helpful to state clearly what the doctrine of the divine simplicity is, according to St.
Thomas, because no small number of recent authors, many of them even commenting on the
thought of St. Thomas, have taken the primary meaning of divine simplicity to be the following:
that all of God’s attributes are in reality identical, so that His power is His wisdom, which is also
His esse, which is also His goodness, etc. While these claims are true (something to which St.
Thomas alludes in q. 3 a. 3), this is nevertheless not the primary meaning of simplicity: simplicity
means the absence of composition.
13.3. A Brief Metaphysics of Creation
Before proceeding to a consideration of other divine attributes, we should make some brief
remarks about the notion of creation as St. Thomas understands it. Already within q. 3, St. Thomas
has offered arguments for (a) the identity of essence and esse in God and (b) the real distinction of
essence and esse in all other things. Because in any being in which essence and esse are distinct,
esse must be caused by something extrinsic agent, God must at a minimum be the ultimate efficient
cause of all existing things. The activity according to which God causes things to exist is called
creation. We will very briefly summarize some important Thomistic claims concerning creation.
(1) In Summa theologiae I q. 45 a. 1, St. Thomas asserts that by creation he means the
emanation of all beings (those under ens commune) from subsistent esse, that is, from God.
(2) In a. 5 of this same question, St. Thomas explains that only God has the power to
create, and it is impossible for God to communicate the power to create to any creature.
(3) In a. 2 of the same question, St. Thomas explains that creation insofar as it is something
in creatures, is the relation of dependence that the creature has with respect to God. Every creature
is related to God as something caused to its efficient cause. This relation is a real relation between
creatures and God, but there is not any corresponding real relation from God to creatures.
(4) St. Thomas sharply distinguishes between creation and generation (that is, substantial
change that produces a new substance). Generation presupposes pre-existing prime matter, which
is the subject of substantial change. But God creates ex nihilo, presupposing absolutely no subject.
For this reason, it would be a most serious mistake to think of creation as presupposing essences as
already-existing things that receive esse from God. When we say that God causes esse, we do not
mean to exclude that God also causes a thing’s essence: indeed, God must cause both a thing’s esse
and its essence. Or, to put it more simply, what God causes to exist are the individuals of various
essential kinds. God does not create just esse or essences, but essence-esse composites, i.e., beings.
(5) Creation is not a “one-time” event in the past or at the beginning of the existence of a
given thing. Rather, God continually causes things to exist, sustaining all creatures in existence. If
God did not do this, then creatures would immediately cease to exist.
Carl: Metaphysics 113
14. Divine Perfection
In Summa theologiae I q. 4 and 6, St. Thomas treats the divine perfection and the divine
goodness.
a. 1: God is perfect
St. Thomas’s argument for the perfection of God in q. 4 a. 1 is stated very briefly. He notes
that some ancient thinkers did not attribute perfection to the first principle of the universe, because
they thought that the first principle was something material, which is necessarily imperfect.
However, St. Thomas asserts that the first principle, God, is not a first principle as a material cause
(which was the most foolish opinion expressed by David of Dinant), but rather as an efficient
cause, and therefore God must be most perfect. St. Thomas explains that an agent, as such, is
always in act; therefore the first agent must be most actual. But perfection is according to a thing’s
degree of actuality, and therefore God, being pure and total actuality, must be most perfect.
The notion of perfection employed here is this: to be perfect is to lack nothing of the mode
of perfection appropriate to a thing. Because God is pure act and is without any potency, it cannot
be the case that He is imperfect, i.e., that He lacks anything appropriate to Himself. Therefore, He
must be perfect.
It is absolutely essential to note that the notion of perfection expressed here is a quasinegative notion: to be perfect is not to lack any actualization that is appropriate to a thing’s mode of
perfection. As Msgr. Wippel analyzes the argumentation for divine perfection, it represents a
crucial turning point in the via negativa: the via negativa arrives at a kind of double negation when
it denies the lack of any appropriate perfection to God.90 Perfection is a negative name with, as it
were, positive implications, as we will see in the following article.
a. 2: the perfections of all things are in God
Perfection as St. Thomas argues for it in a. 1 is a negative name. In a. 2, St. Thomas draws
from this negative name some positive implications, in arguing that God is universally perfect so
as not to lack any excellence found in any genus. He argues for this in two ways:
(1) Whatever perfection exists in an effect must be found in its efficient cause, either
according to the same form (if the cause is a univocal agent) or in a more eminent degree (if the
cause is an equivocal agent). Now, whereas to pre-exist in a material cause (that is, in the principle
of potency) is to exist in a less perfect way than the effect, to pre-exist in an efficient cause is to
exist in a more perfect way. For example, the dog that is capable of causing another dog to exist is
more perfect than the dog that initially comes to exist as an effect. Therefore, because God is the
first efficient cause of everything that exists, all of the perfections of things must pre-exist in Him.
However, He is not a univocal agent, because He does not share a genus with any creature; and
therefore all perfections of creatures must pre-exist in God in a more eminent way.
-By a univocal agent, St. Thomas means an efficient cause that shares in the same species
as its effect. For example, a man causes a man through reproduction, and fire causes fire. By an
equivocal agent, St. Thomas means a higher agent that produces an effect despite not sharing in the
same species. For example, he thinks that the sun is an equivocal cause of heat: that is, he thinks
that the sun is not actually hot in the same way that things in the sublunary are hot.
(2) God is ipsum esse per se subsistens: existence itself subsisting per se. Therefore, He
must contain within Himself the entire perfection of being, just as if there were some separate,
90See Wippel 517, 529.
Carl: Metaphysics 114
subsisting heat, it would necessarily lack nothing of the entire virtue of heat. But every created
perfection is included in the perfection of being, because anything is perfect just insofar as it has
esse in some mode. That is, every perfection is a mode of esse. The being that is subsistent esse
itself therefore cannot lack the perfection of any thing.
-From the identity of essence and esse in God, St. Thomas argues that God cannot lack any
of the perfections of created things, because every perfection is just a mode of esse.
a. 3: that creatures are like God
Finally, St. Thomas argues in a. 3 that creatures possess a likeness to God, not according to
univocal agreement in some form in the same mode, but according to a diminished sharing in a
formality that is analogically common. This is the foundation of his later elaboration on the
analogical character of all divine naming.
In articulating this, St. Thomas offers a division of the ways in which one thing can be like
another:
(1) Some things are alike because they share in the same form according to the same ratio
and in the same mode. Such things are not only alike, but equal. For example, two things of equal
whiteness are equally alike in whiteness. This is the most perfect form of likeness.
(2) Some things are alike insofar as they share in a form according to the same ratio, but
not in the same mode or measure. For example, two things can both be white, but one is more
white than the other. This is an imperfect likeness.
(3) Some things are alike insofar as they share in the same form, but not according to the
same ratio. This occurs in the relationship between a univocal cause and its effect.
At this point, St. Thomas introduces two crucial axiomatic claims:
(a) Every agent produces something like itself: omne agens agit sibi simile.
(b) Everything acts according to its form: unumquodque agit secundum suam formam
From these principles St. Thomas concludes:
As we shall see in subsequent discussion of the names of God and of the analogy of being
between God and creatures, this principle that omne agens agit sibi simile is absolutely crucial. It is
because every agent produces something like itself that there will be an analogical likeness
between creatures and God.
Therefore if there is an agent not contained in any genus, its effect will even more distantly
reproduce the form of the agent, not, that is, so as to participate in the likeness of the agent’s form
according to the same specific or generic ratio, but only according to some sort of analogy; as esse
is common to all. In this way all created things, insofar as they are beings, are like God as the first
and universal principle of all being.
Carl: Metaphysics 115
15. Divine Naming: the Threefold Way
Having established the various divine attributes treated in Ia qq. 3-11, St. Thomas proceeds
in qq. 12-13 to a discussion of how God is known by us and how God is named. Since we have
already treated in part the question how God can be known by us—as a cause is known, albeit
imperfectly, from its effects—we will here only attend to some points we haven’t yet emphasized.
15.1. The Impossibility that a Creature Should Comprehend God
No creature can see the essence of God by its own natural power
No creature seeing the essence of God can comprehend Him
15.2. The Threefold Way of Knowing and Naming God
The triplex via
Res significata and modus significandi
Carl: Metaphysics 116
16. Analogy II: the “Transcendental” Analogy and the Divine Names
The doctrine of analogy in St. Thomas is most famously applied on what we earlier called
the “transcendental” level, that is, between God and creatures. We will now proceed to a
consideration of the notion of analogy between God and creatures, particularly with regard to the
analogical character of being.
With regard to the analogy between God and creatures, the thought of St. Thomas appears
to have undergone some development and modification over the course of his writing career.91 In
brief, we can trace two significant developments:92
(1) From a primary formulation of analogy early in his career as four-term proportionality
to a later primary formulation of analogy as the relation of one thing to another. We will examine
this development by comparing a text from the early De veritate with a couple of texts from later
in St. Thomas’s career.
(2) From an earlier emphasis on the exemplar formal causality of the divine essence to a
later emphasis on the efficient causality of God, with the consequent likeness between creatures
and God. This development can be helpfully examined by comparing a text from the Commentary
on the Sentences with some texts from after the period of the Summa contra Gentiles.
16.1. Analogy as Proportion(ality) and Analogy as a Relation of One to Another
Analogy as Proportionality: De veritate q. 2 a. 11
De veritate q. 2 a. 11 asks whether or not knowledge (scientia) is predicated equivocally or
univocally of God and of creatures.93 St. Thomas denies that there could be any univocal
predication of such a term with respect to God and creatures. Univocal predication occurs when the
same term is predicated of two realities according to exactly the same ratio: but because creatures
only imperfectly imitate the divine essence, it cannot be the case that their perfections—including
knowledge—could equal the perfections of God that they imitate. Therefore the perfections of
creatures and the perfection of God must be understood according to diverse rationes.
However, St. Thomas argues that such terms that are truly predicated of both God and
creatures cannot be predicated in a purely equivocal way. If there were not some likeness between
creatures and God, then God could not know creatures by knowing Himself (St. Thomas has
already established that God does know creatures in just this way earlier in q. 2). Furthermore, if
terms predicated of both creatures and God were all purely equivocal, then it would be impossible
to reason from creatures so as to arrive at some knowledge of God. Finally, if terms were purely
equivocal between God and creatures, we would not have any basis upon which to know in any
way the ratio of these terms as they are applied to God; and therefore, any name could be as
fittingly predicated of God as well as any other, which is absurd.94
St. Thomas concludes that therefore scientia must be predicated neither entirely univocally
91In my view, perhaps the single best treatment of the analogy of being, particularly on the transcendental
level, is that found in Bernard Montagnes’ The Doctrine of the Analogy of Being according to Thomas
Aquinas, tr. E. M. Macierowski (Milwaukee: Marquette, 2004). The historical developments noted in
these notes are dealt with at length in this book, as well as in Wippel 543-72.
92However, it must be noted that these are generalizations, and the issue is considerably more complicated
than this brief summary suggests.
93See Wippel 550-55.
94See Wippel 551 for his summary of these arguments.
Carl: Metaphysics 117
nor purely equivocally of God’s scientia and of ours. Instead, this term is predicated analogously:
St. Thomas here distinguishes between a two-term proportion, in which there is some
determinate relation between the two terms of the relation, and a four-term proportionality, in
which there is an agreement not in a determinate way between two things, but rather between two
proportions. The former case—proportion—is how two is related to one as double. The latter
case—proportionality—is how the relation of four and two is in agreement with the relation of six
and three or of twenty and ten.
St. Thomas then proceeds to note that the first kind of analogy of proportion occurs in the
analogical predication of the term being with respect to accidents and substance: “Being is
predicated of substance and accident because of the relation which accident has to substance.” This
is what we have previously called the horizontal analogy of the categories, and in the terminology
of De veritate q. 2 a. 11, the horizontal analogy is an analogy of proportion. The determinate
relation that exists between an accident and a substance is that the former inheres in the latter as in
its subject cause.
He now reaffirms that wherever terms are predicated analogously according to proportion,
there must be some determinate relation (aliquam determinatam habitudinem) between those
Instead it is predicated analogously, or, in other words, according to a proportion (secundum
proportionem). Since an agreement according to proportion can happen in two ways, two kinds of
community can be noted in analogy. There is a certain agreement between things having a
proportion to each other from the fact that they have a determinate distance between each other or
some other relation to each other, like the proportion which the number two has to unity in as far as
it is the double of unity. Again, the agreement is occasionally noted not between two things which
have a proportion between them, but rather between two related proportions—for example, six has
something in common with four because six is two times three, just as four is two times two. The
first type of agreement is one of proportion (proportionis); the second, of proportionality
(proportionalitatis).
those terms predicated according to the first type of analogy, there must be some definite
relation between the things having something in common analogously. Consequently, nothing can
be predicated analogously of God and creature according to this type of analogy; for no creature
has such a relation to God that it could determine the divine perfection.
Carl: Metaphysics 118
things in which there is something in common by analogy. He argues from this to the following
conclusion. Having distinguished between analogy as two-term proportion and as four-term
proportionality, St. Thomas excludes the first type of analogy as regards the common predication
of terms with respect to God and creatures. Concerning the second type of analogy, proportionality,
he continues:
St. Thomas thus allows the possibility that a term might be predicated of both God and
creatures according to analogy, but only according to an analogy of four-term proportionality. He
continues:
St. Thomas distinguishes here between metaphorical names and names that can be
properly predicated of God. What distinguishes the former names is that the very definition of a
metaphorical name there is included matter: that is, any name of the essence of something
corporeal cannot be predicated of God except metaphorically. But where a name’s definition
contains no matter, it will be possible to find between God and creatures an agreement of the
second kind indicated above, that is, of four-term proportionality.
Unfortunately, St. Thomas only gives examples of names that can be predicated
analogously—being, good, etc.—without carefully spelling out the nature of the proportionality.
He seems to mean something like this: the being of a creature is related to its goodness as the
being of God is related to His goodness. This interpretation seems confirmed by what St. Thomas
asserts in De veritate q. 23 a. 7 ad 9:
But in the other type of analogy, no definite relation is involved between the things which have
something in common analogously, so there is no reason why some name cannot be predicated
analogously of God and creatures in this manner.
this can happen in two ways. Sometimes the name implies something belonging to the thing
primarily designated which cannot be common to God and creature even in the manner described
bove. This would be true, for example, of anything predicated of God metaphorically, as when
God is called lion, sun, and the like, because their definition includes matter which cannot be
attributed to God. At other times, however, a term predicated of God and creature implies nothing
in its principal meaning which would prevent our finding between a creature and God an
agreement of the type described above. To this kind belong all attributes which include no defect
nor depend on matter for their act of existence, for example, being, the good, and similar things.
Carl: Metaphysics 119
Curiously, in this text, St. Thomas first raises the possibility that there can be a direct
proportion between creature and God, according to any of the relations that can be said to exist
between creature and God—for example, the dependence relation of creation. However, he
qualifies that this is an extended sense of the term proportion, rather than its proper meaning. He
then proceeds to explain, as an alternative solution to the objection, the way in which there can be
a proper proportionality between creatures and God: as a creature stands to what is its own, so God
stands to those things which belong to Him. This implies that our suggestion above was correct:
Because man is infinitely distant from God, there cannot be a proportion between him and God in
the proper sense of proportion as found among quantities, consisting of certain measure of two
quantities compared to each other. Nevertheless, in the sense in which the term proportion is
transferred to signify any relationship of one thing to another. . ., nothing prevents our saying that
there is a proportion of man to God, since man stands in a certain relationship to Him inasmuch as
He is made by God and subject to Him.
Or the answer could be given that although there cannot be between the finite and the infinite a
proportion properly so called, yet there can be a proportionality or the likeness of two
proportions. . . . Although the finite and the infinite cannot be proportioned, they can be
proportionable, because the finite is equal to the finite just as the infinite is to the infinite. In this
way there is a likeness of the creature to God, because the creature stands to the things which are
its own as God does to those which belong to Him.
Carl: Metaphysics 120
the analogy between creatures and God means that as creaturely being is to creaturely goodness (or
creaturely truth, or creaturely scientia), so is the divine being to the divine goodness (or truth or
scientia), etc.
Having suggested this four-term proportionality as what is meant by the analogy between
creatures and God in the De veritate (and having rejected analogy of proportion), St. Thomas
seems to have almost immediately abandoned this suggestion, as it does not appear in any of his
later writings.95 Even by the time that he finished the De veritate, he has backed off from the strong
claim that no proportion is possible between creatures and God, instead saying that there is
proportion, but just not in the strict sense of mathematical proportion. I would offer the suggestion
(following Montagnes’ account of the development in St. Thomas’s thinking) that the theory of
four-term proportionality was not St. Thomas’s definitive solution to the question of the analogy
between creatures and God. It was instead a solution that he advanced in an early writing, but later
abandoned. We will now turn to a consideration of what replaced the four-term proportionality as
St. Thomas’s account of the analogical character of the divine names.
Summa contra Gentiles cc. 32-34
We will now consider texts from a later writing, the Summa contra Gentiles I cc. 32-34. As
in the De veritate, St. Thomas begins by excluding both totally univocal and purely equivocal
predication of names with regard to God and creatures.96 Two points concerning the arguments
against univocal predication and equivocal predication should be made:
(1) The final argument offered against univocal predication in c. 32 introduces some
important language.
95There are some texts where analogy understood as four-term proportionality is mentioned, but this kind of
analogy is not applied to the common predication of terms with respect to God and creatures.
96See Wippel 555-60 for his careful analysis of the arguments in cc. 32 and 33.
Then, too, what is predicated of some things according to priority and posteriority is certainly not
predicated univocally. For the prior is included in the definition of the posterior, as substance is included
in the definition of accident according as an accident is a being. If, then, being were said univocally of
substance and accident, substance would have to be included in the definition of being in so far as being
is predicated of substance. But this is clearly impossible. Now nothing is predicated of God and creatures
as though they were in the same order, but, rather, according to priority and posteriority. For all things
are predicated of God essentially. For God is called being as being entity itself, and He is called good as
being goodness itself. But in other beings predications are made by participation, as Socrates is said to
be a man, not because he is humanity itself, but because he possesses humanity. It is impossible, therefore,
that anything be predicated univocally of God and other things.
Carl: Metaphysics 121
St. Thomas indicates that nothing that is said “according to priority and posteriority” is
predicated univocally. He gives the example of substance and accident, saying that being is
predicated primarily of substance and secondarily of accident, because accident depends upon
substance and contains substance within its own ratio or definition. Similarly, he says, being and
goodness are predicated of God essentially, because He is ipsum esse and goodness itself; but other
beings are beings and goods by participation. Therefore these terms are not said univocally of God
and creatures. The point to be noted here is that St. Thomas draws a direct comparison between the
horizontal analogy and the transcendental analogy: both are instances of predication “according to
priority and posteriority.” It will be important to recall this later.
(2) In the arguments against purely equivocal predication in c. 33, there is an emphasis on
the relation and likeness that must exist between creatures and God.
Relation:
In this first argument, he says that in purely equivocal predication, “there is no order or
reference of one to another, but it is entirely accidental that one name is applied to diverse things.”
This cannot be admitted in the predication of terms with regard to both God and creatures, because
“we note in the community of such names the order of cause and effect.” That is, there is a relation
of creatures to God, the relation of an effect to the cause, and it is this relation that excludes purely
equivocal predication.
Likeness:
St. Thomas in this next argument says that purely equivocal predication excludes a
likeness between the things named (or at least any likeness having anything to do with the common
name). But creatures are like God (as St. Thomas had proven earlier in the discussion of divine
perfection, just as he does later in the Summa theologiae I q. 4 a. 3). Therefore pure equivocation
can be ruled out.
For in equivocals by chance there is no order or reference of one to another, but it is entirely accidental
that one name is applied to diverse things: the application of the name to one of them does not signify
that it has an order to the other. But this is not the situation with names said of God and creatures, since
we note in the community of such names the order of cause and effect, as is clear from what we have
said. It is not, therefore, in the manner of pure equivocation that something is predicated of God and other
things.
urthermore, where there is pure equivocation, there is no likeness in things themselves; there is only the
unity of a name. But, as is clear from what we have said, there is a certain mode of likeness of things to
God. It remains, then, that names are not said of God in a purely equivocal way.
Carl: Metaphysics 122
In c. 34’s treatment of the analogy between creatures and God, St. Thomas offers a division
of the kinds of analogical predication, but one that is different from that found in the De veritate.
The division of analogy is as follows:
(1) “As many things have reference to something one. For example, with reference to one
health, an animal is healthy as the subject of health, medicine is healthy as its cause, food as its
preserver, urine as its sign.”
(2) “As the order or reference of two things is not to something else but to one of them.
Thus, being is said of substance and accident according as an accident has a reference to a
substance, and not according as a substance and accident are referred to a third thing.”
St. Thomas excludes analogical predication in the first way with regard to the names said
of God and creatures. Instead, he explains that analogy is according to the second mode, that of
analogy according to the reference or relation of one to another. What St. Thomas means to
exclude here is the possibility that God and creatures could share, even by analogical community,
in some perfection that is distinct from both of them: as if there were a being or a goodness distinct
from God and creatures in which both God and creatures could share. This is impossible, because
God is being itself and goodness itself. St. Thomas also means to exclude that God could be said to
participate in some abstracted perfection; there is no tertium quid between God and creatures in
which both commonly participate by analogy.
St. Thomas then explains that although being and goodness belong primarily to God in
reality (because He is esse itself and goodness itself) and to creatures secondarily or in a posterior
way, nevertheless we first know creaturely being and creaturely goodness (and all the other
creaturely perfections from which we name God). Therefore these names are primary to creatures
in the order of discovery (in which we come to name God from His effects), but primary to God in
the order of reality. Similarly, medicine is the cause of health, but it is called healthy from its
effect.
A significant worry: extrinsic denomination
That St. Thomas here draws a comparison between the example of health and the
analogical predication of names such as being and goodness of God has occasioned commentators
to worry that this kind of analogical predication does not reflect any intrinsic similarity between
the various realities. That is, medicine’s being healthy involves no intrinsic likeness to the health of
the body that it causes: this example of analogy is a case of what is called extrinsic denomination,
the naming of something from something extrinsic and not necessarily similar to it. Those thinkers
that have historically favored an interpretation of St. Thomas influenced by Cajetan (which
privileges four-term proportionality as the only analogy that preserves a connection between God
and creatures that speaks to something intrinsic rather than something merely extrinsic) have done
so out of a worry about whether the analogy of one to another can preserve an intrinsic connection
between the being and goodness of a creature and the being and goodness of God.
To answer this concern, we should turn to our next theme, the development in St. Thomas’s
thought from an emphasis on exemplar formal causality as the foundation of analogy, to his
emphasis on efficient causality and its consequent likeness.
Carl: Metaphysics 123
16.2. The Causal Relationship at the Heart of Analogy
Commentary on the Sentences
In In Sent. 1.35.1.4 asks the same question as DV 2.11, whether divine scientia is univocal
with creaturely scientia. Having offered arguments against univocity and pure equivocation, St.
Thomas draws a distinction between two kinds of analogical predication, just as he did in the texts
we have already considered.
In this case there is a distinction between:
(1) Analogical predication according to a common form possessed according to the prior
and the posterior (per prius et posterius). This is how St. Thomas explains the predicamental
analogy of the categories elsewhere in the Sentences Commentary; but here he denies that the
analogy between creatures and God is according to the prior and the posterior.
(2) Analogy according to participation based on an imperfect likeness. This is how St.
Thomas characterizes the transcendental analogy between creatures and God.
Why does St. Thomas exclude analogy according to the prior and posterior in this text?
Here he describes this kind of analogy as “sharing in something one which belongs to both;” this
sounds rather like the analogy of many to one as St. Thomas later distinguishes it in the Summa
contra Gentiles. This suggests that, in the Sentences Commentary St. Thomas does not think that
analogy between God and creatures is according to the prior and the posterior, because he is
concerned to exclude that God and creatures would be thought to share in some common third
thing. St. Thomas later addresses this concern by explicitly distinguishing between the analogy of
many to one and the analogy of one to another, as we saw in the Summa contra Gentiles 1.34:
By his preference for what Montagnes has called analogy according to participation based
on an imperfect likeness, in the Commentary on the Sentences St. Thomas establishes the exemplar
formal causality of the divine essence as the foundation for analogical predication of names. It is
because creatures imperfectly imitate the divine exemplar that certain names can be predicated
analogically of both. Montagnes’ thesis is that DV 2.11 serves to address the quite reasonable fear
that such a comparison according to formal causality would imperil the divine transcendence: a
comparison according to formal likeness would seem to be like the determinate, definite relation
But analogy is twofold. One according to sharing in something one which belongs to them per
prius et posterius; and this analogy cannot be between God and creature, just as univocation
cannot. The other analogy is insofar as one is imitated by another so far as it can, not perfectly
following it; and this is the analogy of a creature to God.
Thus, therefore, because we come to a knowledge of God from other things, the reality in the
names said of God and other things (res nominum de Deo et rebus aliis dictorum) is in God per
prius according to His mode of being, but the meaning of the name (ratio nominis) belongs to Him
per posterius. And so He is said to be named from His effects.
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between two quantities in a mathematical proportion. DV 2.11 offers a solution according to which
imperfect formal likeness can be understood without undermining the divine transcendence.
Omne agens agit sibi simile and consequent likeness
In his later writings, however, St. Thomas emphasizes not the exemplar formal causality of
the divine essence in order to ground analogy, but rather the efficient causality by which God
produces creatures from nothing. According to the principle omne agens agit sibi simile, there is a
likeness between creatures and God necessarily consequent to the act of creation; and thus the
relation and likeness established by efficient causality is what allows the analogical predication of
certain names. There is a relation of one to another that grounds the transcendental analogy: this is
the dependence of creatures upon God as their creating cause.
Unlike the view favored in the Sentences commentary, the relation or proportion grounding
analogy is not directly the comparison between the formal characteristics of God and the imperfect
likeness of those characteristics in creatures; but rather the relation or proportion of efficient
causality is what grounds analogy. That is, against the doctrine of the De veritate, there is a
proportion of God to creatures: that which is established by His being the efficient cause of the
creature. We can briefly cite several texts in which St. Thomas contradicts DV 2.11’s denial that
there is a proportion between creatures and God, by citing the relationship established by efficient
causality as a proportion:97
In DT 1.2 ad 3:
“There is a proportion of creature to God, as caused to cause.”
SCG 3.53:
“Nothing prohibits there being a proportion of the creature to God . . . according to the
relation of effect to cause.”
ST 1.12.1 ad 4:
“There can be a proportion of creature to God, insofar as it is related to Him as an effect to
the cause.”
Montagnes’ theory regarding the developments in St. Thomas’s doctrine of analogy can be
summarized in these stages:
(1) The analogy by participation according to imperfect formal likeness can give rise to the
concern that God’s transcendence is nullified, because analogy seems to consist in a direct
proportion between the perfections of a creature and the perfections of God. That is, analogy can
be said to express just the comparison made between creatures and God, which seems to
undermine the divine infinity and transcendence.
(2) Therefore, St. Thomas proposed the theory of the De veritate to preserve the divine
transcendence. By saying that analogy is based upon a likeness of proportions (the infinite is to the
infinite as the finite is to the finite), St. Thomas can preserve the infinite distance between God and
creatures.
(3) But the solution of the De veritate presents the danger of agnosticism, because it turns
out that there is no direct analogy of being between creatures and God: there is instead an analogy
that compares the relation of God’s knowledge to His infinite being to the relation of creaturely
knowledge to finite creaturely being. Therefore, St. Thomas reverted back in part to the doctrine of
97Cited by Montagnes, 76.
Carl: Metaphysics 125
the Sentences commentary, the analogy by reference to one, but by finding a way that allowed him
to characterize the analogy between God and creatures as one according to priority and
posteriority: the key to this solution is the emphasis on efficient rather than formal causality. As
Montagnes puts it: “Unlike formal causality, efficient causality establishes a relation between
beings and God by which the latter is most intimately present to all that is without ceasing to be
transcendent.”98 By efficient causality (understood with the principle that omne agens agit sibi
simile), St. Thomas can hold both to direct proportion or relation between creatures and God and to
the infinite transcendence of God.
As for this claim that efficient causality establishes a relation by which God is most
intimately present to creatures, while infinitely exceeding them, we should consider the following
from ST 1.8.1 on the divine omnipresence:
From the thesis that God is the proximate efficient cause of esse in creatures, St. Thomas
concludes that God must be most intimately present to all of His creatures: this is because esse is
the act of all acts, the perfection of all perfections, and the most formal and actual principle.
98Montagnes 79.
God is in all things; not, indeed, as part of their essence, nor as an accident, but as an agent is
present to that upon which it works. For an agent must be joined to that wherein it acts
immediately and touch it by its power; hence it is proved in Physics VIII that the thing moved and
the mover must be joined together. Now since God is very being by His own essence, created being
must be His proper effect; as to ignite is the proper effect of fire. Now God causes this effect in
things not only when they first begin to be, but as long as they are preserved in being; as light is
caused in the air by the sun as long as the air remains illuminated. Therefore as long as a thing has
being, God must be present to it, according to its mode of being. But being is innermost in each
thing and most fundamentally inherent in all things since it is formal in respect of everything found
in a thing, as was shown above. Hence it must be that God is in all things, and innermostly.
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16.3. Cajetan on Analogy
It is fitting, both in the study of Thomistic metaphysics in general, but also in particular in
the study of St. Thomas at a Dominican studium, to consider at least briefly the account of analogy
given by Tommaso de Vio Cardinal Cajetan, the great commentator on St. Thomas. With regard to
the issue of analogy, Cajetan’s account of analogy (in De nominum analogia) has had a tremendous
impact on Thomists for centuries. The position on analogy that we have sketched so far—
influenced primarily by Montagnes—is in no small part a reaction against the central elements of
Cajetan’s theory of analogy.
The context and purpose of the De nominum analogia
As Joshua Hochschild emphasizes in The Semantics of Analogy (his extremely helpful
book on Cajetan’s De nominum analogia), generally speaking Thomist critics of Cajetan in the 20th
century took it to be the case that the right question to bring to bear on Cajetan’s account is this: Is
Cajetan’s account of analogy faithful to the writings and thought of St. Thomas himself? Is it the
right interpretation? However, Hochschild argues that this is the wrong question, the wrong
criterion for judging Cajetan’s treatise on analogy. Rather, one must read Cajetan’s account as a
relatively independent attempt to offer a semantic, logical account of analogy that is sufficient to
answer two objections to analogy that are rooted in the thought of Scotus. These two objections
can be roughly stated as follows.
Objections against analogy inspired by Scotus:99
1) At the core of any so-called analogical predication, there must be some element of
univocity, or else there will only be equivocation. That is, the claim that analogy is a proper mean
between univocity and equivocation cannot be maintained. (For this reason, on the Scotistic
account, there must be a univocal concept of being and of any other “transcendental” notions.)100
2) Any use of non-univocal terms will cause the fallacy of equivocation when those terms
are employed in reasoning. That is, analogical terms as St. Thomas conceives of them will cause
the fallacy of equivocation; and since metaphysics employs analogical terms almost exclusively,
metaphysics will not be a science.
It is not our purpose here, however, to consider how it is that Cajetan’s account is an
attempt to answer these objections. One can and should look to Hochschild’s work to consider this
issue—and as Hochschild emphasizes, this is the most appropriate way to approach Cajetan’s
treatise insofar as one is interested in evaluating his work.
Cajetan’s theory and the background in St. Thomas
All that being said, the historical question of whether Cajetan’s account is also the best
interpretation of St. Thomas’s understanding of analogy can still be asked—it should only be borne
in mind that any negative answer would not necessarily be a criticism of Cajetan himself. As
Hochschild himself notes, this is the primary question that has been asked by Thomists since the
mid-20th century, in reaction against the general acceptance of Cajetan’s theory by previous
Thomists. It is not the best question for evaluating Cajetan’s thought—but it is a question to be
considered, nevertheless.
My intention here is only to offer a brief sketch of what might called the standard
interpretation of Cajetan’s theory as an interpretation of St. Thomas, even though we must
99 Hochschild, 39 ff.
100 Scotus’s notion of a “transcendental” is different from St. Thomas’s, at least terminologically: for Scotus,
any term that is predicated in common of both God (the infinite) and creature (the finite) is
transcendental.
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acknowledge with Hochschild that this was not Cajetan’s primary purpose in the De nominum
analogia. To do this, we must first cite a key text from St. Thomas’s Commentary on the Sentences
1.19.5.2 ad 1. This article asks whether or not all things are true by virtue of uncreated truth (utrum
omnia sint vera veritate increata). The first objection argues:
The objection contends that it follows immediately from analogical predication that there
is one primary instance from which all the analogates are denominated; and so if true is an
analogous term, then there must be one primary instance of truth whereby all true things are called
true.
In his reply to this objection, St. Thomas draws a threefold distinction among cases or
ways in which something can be said according to analogy:
The three-fold division of analogy in In Sent. 1.19.5.2 ad 1
(a) according to notion but not according to being (secundum intention tantum, et non
secundum esse)
-This occurs when one notion is related to several things per prius et posterius, which
notion nevertheless only has being (esse) in one of these things.
-For example, the notion of health is related to animal, urine, and a diet in diverse ways,
according to priority and posteriority; and yet this predication is not secundum esse,
because the being of health (esse sanitatis) is present only in the animal (its subject).
(b) according to being but not according to notion (secundum esse et non secundum
intentionem)
-This occurs when several things share equally in some common notion, but that notion
does not have being according to the same ratio in all of these things.
-For example, one can consider all bodies as sharing equally in body taken as a genus (as
one does in the Porphyrian tree), even though in being the celestial bodies and sublunary
bodies do not have being according to the same ratio.
-St. Thomas goes on to explain that in this case, whereas the logician treats body
univocally, the metaphysician recognizes that body is said analogically of these different
kinds of body: this is because the metaphysician considers things secundum esse.
(c) according to notion and according to being (secundum intentionem et secundum esse)
-This occurs when things share equally neither in a common notion nor in being.
-For example, being (ens) is said of substance and accident in this way. Also, it is in this
way that truth, goodness, and other names of this kind are said analogically of God and
creatures.
-In this case it is necessary that the common nature (natura communis) named
For . . . true is said analogically of those things in which there is truth, just as health [is said
analogically] of all healthy things. But one in number is the health from which animal is
denominated healthy as [health’s] subject, and medicine healthy as its cause, and urine healthy, as
its sign. Therefore it seems that one is the truth by which all things are called true.
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analogically have some being in each of the things of which it is said, but differing
according to greater and lesser perfection.
St. Thomas concludes the response to the objection by arguing that truth has being in all of
the analogates (and not just in God, understood as the primary analogate), but not being according
to the same perfection. Therefore, there are diverse truths, and not just one truth from which all
other things are denominated true (in a purely extrinsic fashion).
Now, Cajetan’s presentation of analogy mirrors this threefold presentation, and the famous
Cajetanian names for the kinds of analogy are names that replace the formulas found in In Sent.
1.19.5.2 ad 1: Cajetan calls these analogy of attribution (analogia attributionis), analogy of
inequality (analogia inaequalitatis), and analogy of proportionality (analogia proportionalitas).101
Cajetan’s examples of each of these kinds of analogy are the same as the examples found in In
Sent. 1.19.5.2 ad 1, and in each case he references this text of St. Thomas, citing the Thomistic
formula.
Cajetan’s fundamental division of analogy:102
(a) analogy of attribution: this is the kind of analogy according to which healthy is said of
the animal, medicine, and urine. It is parallel to St. Thomas’s analogy secundum intentionem
tantum, et non secundum esse.
-Cajetan emphasizes that in this analogy, the primary analogate is a part of the definition of
the secondary analogates: the health that is in the animal as its subject is part of the
definition of healthy when it is predicated of medicine or urine.
-Cajetan contends that it is analogy of attribution that is divided into analogy of two to a
third (analogia duorum ad tertium) and analogy of one to another (analogia unius ad
alterum) by St. Thomas.103
-Cajetan does not consider this to be analogy except in an abusive sense, because the
common nature is present intrinsically in only one of the analogates. Medicine and urine
are not healthy, intrinsically, but are only denominated as healthy because of their relations
(as cause and sign) to health. He notes that from the logician’s perspective (which
Hochschild argues is Cajetan’s own perspective in De nominum analogia) analogy of
attribution is equivocation.
(b) analogy of inequality: this is the kind of analogy according to which body is said of
both celestial bodies and sublunary bodies. It is therefore parallel to St. Thomas’s analogy
secundum esse et non secundum intentionem.
-From the perspective of the logician, as St. Thomas himself says, this kind of analogy is
really univocity. Therefore, while on the one hand this kind of analogy does not raise, for
Cajetan, the troubling worries about equivocation in reasoning; on the other hand, there’s
no reason to give any extended treatment to this kind of analogy in a treatise on analogy
from a semantic or logical perspective.
(c) analogy of proportionality: this is what Cajetan offers as parallel to St. Thomas’s
analogia secundum intentionem et secundum esse. Interpreting Cajetan’s theory as an interpretation
101 De nominum analogia, c. 1 (4).
102 Cajetan treats analogy of inequality first, because he does not think it is really analogy at all; I have
reordered the treatment to reflect the parallels with In Sent. 1.19.5.2 ad 1, which, again, Cajetan himself
cites.
103 DNA, c. 2 (19).
Carl: Metaphysics 129
of St. Thomas, this identification would fatefully combines the account of analogy from DV 2.11
with the division of analogy in In Sent. 1.19.5.2 ad 1.
-As an initial example, Cajetan offers the following: bodily vision and intellectual vision
are both called vision, because as the intellect is comparable to the eye, insofar as the
intellect is related to its object in a manner similar to how the eye is related to its object.
-It is only this kind of analogy that is analogy properly speaking, for Cajetan. It is a true
mean between equivocation and univocity, and he defends the claim that one can employ
terms analogous in this way in one’s reasoning without committing the fallacy of
equivocation.
-Following the suggestion of In Sent. 1.19.5.2 ad 1, Cajetan treats the analogy of being on
both the “horizontal” and the “transcendental” levels according to the analogy of
proportionality.
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17. Divine Operations: Knowledge, Will, Power
Just as we offered some brief commentary on the meaning of the various divine names
treated from Ia qq. 6 – 11 in the Summa theologiae, so now we will offer some brief commentary
on the names treated by St. Thomas in connection with the divine operation.
St. Thomas introduces this section of the Summa theologiae (Ia qq. 14 – 26) in the
following way, in the prologue to q. 14:
These latter divine names are discussed under the heading of divine operations. Now, in
finite creatures, operations are accidents that are distinct from the substances in which they exist.
In God, there is no substance-accident composition, and therefore each of these names of divine
operations names the divine essence itself, but understood according to a distinct ratio.
14.1. Divine Knowledge
How it is established that there is knowledge in God
Concerning argumentation for knowledge in God in q. 14 a. 1, it should be noted that
curiously St. Thomas does not base any argument upon the claim that God is perfect or possesses
in a more eminent way the perfections of all things. (St. Thomas does offer this sort of argument
for divine intelligence in the Summa contra Gentiles I c. 44). Instead, he simply argues that God’s
having knowledge follows from His absolute immateriality: to be an immaterial substance is to be
an intellectual substance, because an intelligent being is one that can naturally possess the form of
something besides itself. Immateriality is the cause of intelligence. Since God is immaterial in the
highest degree, it follows that He also is the highest in knowledge.
In the subsequent articles of q. 14, St. Thomas explains that God primarily knows and
comprehends Himself, because in God there is no distinction between His intellect and His
essence: therefore the primary object of the divine intellect is just the divine essence itself. God
comprehends Himself because the power of His intelligence is equal to the infinite perfection of
His essence, because He is pure act without any potency or principle of limitation.
The divine ideas
As regards the knowledge of things besides Himself—that is, the things that He creates—
St. Thomas explains that God knows other things by knowing Himself, insofar as He is the cause
After consideration of those things that pertain to the divine substance, remaining to be considered
are those things that pertain to His operation. And since one kind of operation is that which
remains in the one operating, but another is that which proceeds to an exterior effect; first we will
deal with knowledge and will (for to understand is in the one understanding, and to will is in the
one willing); and afterward about the power of God, which is considered as the principle of the
divine operation proceeding into exterior effects. . .
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of other things that are like Him as various imperfect imitations of His essence. In q. 15, St.
Thomas discusses the notion of the divine ideas. The divine ideas are the exemplar forms of the
things that God creates, the “plans,” as it were, according to which God creates particular things:
the divine ideas are thus analogous to the ideas of artisans and builders.
The divine ideas are many, because God can create many different kinds of things. The
divine ideas are just this: God’s understanding of the various ways in which His essence can be
imperfectly imitated by creatures. Every creature is unlike and falls short of God, but some are
unlike God in more ways or to a greater degree than others. For example, a lion is less unlike God
than a rock; and a human being is less unlike God than a lion.
It should also be noted that the divine ideas according to which God creates are not His
ideas of genera or species (although He does have such ideas), but rather His ideas of individuals.
The individual essence of a given corporeal substance includes not just its matter taken universally,
but its particular matter. God understands the individual essence of a corporeal substance in a way
that no human intellect can, by understanding its particular matter as well as its form.
14.2. Divine Will
Divine will is treated in Summa theologiae I q. 19. That God has will is argued for from
the fact that will naturally follows upon intellect, because will is nothing but the intellectual
appetite, where appetite is understood as inclination towards the good. Because God is the supreme
and most perfect good, He primarily wills His own goodness. Everything else that God wills is
ordered to Himself as an end, so as to allow creatures to share in His infinite goodness.
One of St. Thomas’s central concerns (in aa. 3 and 5) is to argue that God’s will is free: it is
not the case that God wills whatever He wills necessarily. God does will His own goodness
necessarily, but all of those things that He wills for the sake of His goodness He wills freely. (In a
similar way, freedom in the human will concerns the election of the means by which an intended
end is pursued.) Indeed, St. Thomas affirms that no cause can be assigned for the divine will,
because just as God understands all things in understanding Himself, so He wills what He wills in
willing His goodness. That is, by the same simple act God wills both Himself and whatever else He
wills. Another way of recognizing the same claim, then, is to remember that God’s intellect and
will are in reality both identical with the divine essence, and the divine essence cannot be related to
itself as a cause.
14.3. Divine Power and Omnipotence
Although there is no passive power in God—that is, a capacity to be acted upon by
something else—there is active power, the capacity to produce an effect distinct from Himself.
Because God is pure act, it belongs to Him to be capable of acting as an efficient cause—indeed, it
should be recalled that the foundation for establishing God’s existence and many of His attributes
was the recognition that there must be a first efficient cause of all things. The notion of active
power is the principle of an external effect. Because God is the principle of external effects, as an
efficient cause, He is said to be active power. Indeed, just as with His other attributes, God is
identical with His power.
St. Thomas also argues for the two very closely related claims that God’s power is infinite
and that He is omnipotent. These are slightly distinct claims: God is said to possess infinite power
because His power is identical with His infinite essence. It is the infinite character of God’s power
that serves to explain why God is capable of the act of creation, whereas no other being is capable
of creating anything ex nihilo. That is, the claim that God’s power is infinite is primarily a claim
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concerning the degree of the divine power: by His power God is capable of doing something that
requires unlimited power.
By contrast, to say that God is omnipotent means that God is capable of doing absolutely
anything that is possible, i.e., anything that does not involve a contradiction. In articulating the
notion of absolute possibility in this way, St. Thomas is dependent upon Aristotle’s Metaphysics,
which he references in q. 25 a. 3. God can do anything that does not involve or imply a
contradiction. To say that God cannot do what involves a contradiction is not to place any limit on
God’s power, because what is contradictory simply cannot be.
Significance of the late treatment of divine power
It is worth taking note of the fact that St. Thomas treats the notion of divine power and
omnipotence virtually last in the order of the divine names. That is, power or omnipotence is not
the first thing to be established concerning God (even though one could establish it much earlier in
the order of the attributes, since the arguments for God’s power depend upon His being an efficient
cause and pure act, things established by Ia q. 3 a. 1). In contrast to later theology of the early 14th
century, St. Thomas does not place a central emphasis on the notions of divine will and power. He
does argue both that God is free and that God is omnipotent, but these are not the first things to be
said concerning the divine essence.
By contrast, theologians such as Ockham afford such a central place to the notion of divine
omnipotence that it becomes as it were one of the absolutely first principles of theology and
philosophy. For example, Ockham argues from the divine omnipotence—which implies that God is
capable of producing immediately by His power any effect that can be produced by any secondary
(i.e., creaturely) cause—to metaphysical conclusions, such as the denial of the reality of any
categories of being besides substance and quality. In St. Thomas, although divine omnipotence is
affirmed, it is not the first or most important thing to be said concerning the divine essence. After
all, it concerns more what God can hypothetically do, rather than what He does in fact will to do.

 

Carl: Metaphysics 1
Metaphysics: Fall 2020
Brian Thomas Carl, Ph.D.
Center for Thomistic Studies
Schedule of Topics & Readings
A. What is Metaphysics?
0. Introduction to the Study of Metaphysics: Wippel 3-22, In Met. pr.
1. The knowledge of being: Wippel 23-44, In DT 5.3
2. Separatio and the knowledge of being as being: Wippel 44-62, In DT 5.3
B. Being and beings: Analogy and Participation
3. The one and the many: Wippel 65-73
4. Analogy I: the meaning of analogy and the “horizontal” analogy: Wippel 73-93
5. Participation: Wippel 94-131
C. The Composite Character of Ens Commune
6. Real composition and distinction of essence and esse: Wippel 132-161
7. Substance-accident composition: Wippel cc. 7-8, esp. pp. 197-228, 253-61
8. Matter-form composition in corporeal substances: Wippel c. 9, esp. 312-327, 351-75
9. Comparison and coordination of the modes of composition: potency and act
D. Transcendentals
10. The transcendentals: DV 1.1; In Met. 4.2, 10.3; ST 1.16.1-4; ST 1.5.1-4
E. Natural Theology I: God’s Existence
11. How God is known through natural reason: ST 1.2.1-2
12. Argumentation for God’s existence: the first way: ST 1.2.3, Wippel 444-59
F. Natural Theology II: Knowing and Naming God
13. Simplicity: God as ipsum esse per se subsistens: ST 1.3.1-8
14. Establishing divine perfection: ST 1.4.1-3
15. Divine naming: the threefold way: ST 1.12
16. Analogy II: “transcendental” analogy and divine names: ST 1.13
17. Divine operations: intellect, will, power: ST 1.14, 1.19, 1.25
Carl: Metaphysics 2
ABBREVIATIONS
CT Compendium theologiae
De ente De ente et essentia
De prin. De principiis naturae
De malo Quaestiones disputatae de malo
De pot. Quaestiones disputatae de potentia Dei
De spirit. creat. Quaestio disputata de spiritualibus creaturis
De ver. Quaestiones disputatae de veritate
In De an. Sententia libri De anima
In DN In librum Beati Dionysii De divinis nominibus expositio
In DT / SBDT Super Boetium de Trinitate
In Ethic. Sententia libri Ethicorum
In Meta. In duodecim libros Metaphysicorum Aristotelis expositio
In Per. Expositio libri Peryermenias
In Phys. In octos libros Physicorum Aristotelis expositio
In Post. Expositio libri Posteriorum
In Sent. Scriptum super libros sententiarum magistri Petri Lombardi
LR Lectura romana in primum Sententiarum Petri Lombardi
Quodl. Quodlibeta
Resp. (108) Responsio ad magistrum Ioannem de Vercellis de 108
articulis
SCG Summa contra Gentiles
ST Summa theologiae
Carl: Metaphysics 3
1. The Knowledge of Being
As already indicated, metaphysics is the philosophical science that studies being, or, to be
more precise, being as being. What does this mean? It will be the purpose of the first two sections
of the course to begin to address this question. We will begin with a consideration of the following
question: how is being known by human beings?
1.1. Background: Apprehension and Judgment
In order to understand the Thomistic position concerning the knowledge of being, it is
necessary first to recall the distinction, drawn in logic (as well as in the study of human nature and
in epistemology), between apprehension and judgment as two of the three operations (along with
reasoning) of the human intellect.
Apprehension
By the act of apprehension, the human intellect grasps the quiddity or essence of a
(corporeal) reality: this is to say that the intellect grasps what something is. We can consider a text
from St. Thomas’s early De ente et essentia, c. 1, for a treatment of what he means by the term
quiddity:
Et quia illud per quod res constituitur in proprio
genere vel specie est hoc quod significatur per
diffinitionem indicantem quid est res, inde est
quod nomen essentiae a philosophis in nomen
quidditatis mutatur; et hoc est etiam quod
Philosophus frequenter nominat quod quid erat
esse, id est hoc per quod aliquid habet esse quid.
Dicitur etiam forma, secundum quod per formam
significatur certitudo uniuscuiusque rei, ut dicit
Avicenna in II Metaphisicae suae. Hoc etiam alio
nomine natura dicitur, accipiendo naturam
secundum primum modum illorum quatuor quod
Boetius in libro De duabus naturis assignat:
secundum scilicet quod natura dicitur omne illud
quod intellectu quoquo modo capi potest, non enim
res est intelligibilis nisi per diffinitionem et
essentiam suam; et sic etiam Philosophus dicit in V
Metaphysicae quod omnis substantia est natura.
Tamen nomen naturae hoc modo sumptae videtur
significare essentiam rei secundum quod habet
ordinem ad propriam operationem rei, cum nulla
And since that through which a thing is constituted
in its proper genus or species is what is signified
through the definition indicating what the thing is,
therefore the name of essence was changed by
philosophers to the name “quiddity”; and this is
also what the Philosopher frequently calls “the
what it was to be,” that is, that through which
something has a [certain] kind of being. It is also
called form, inasmuch as through form the reality
of any thing is signified, as Avicenna says in Book
II[I] of his Metaphysics. This is also by another
name called the nature, taking nature according to
the first meaning of the four which Boethius
assigns in the book Of [the Person and] the Two
Natures: according to the way, namely, that
everything which can be received in any way by
the intellect is called nature, for a thing is not
intelligible except through its definition and
essence; and thus the Philosopher also says in
Book V of the Metaphysics that every substance is
a nature. Nevertheless the name of nature taken in
Carl: Metaphysics 4
res propria operatione destituatur; quidditatis vero
nomen sumitur ex hoc quod per diffinitionem
significatur. Sed essentia dicitur secundum quod
per eam et in ea ens habet esse.
this way seems to signify the essence of a thing
insofar as it has an order to the proper operation of
the thing, since no thing lacks its proper operation;
but the name of quiddity is taken from what is
signified through the definition. But it is called
essence insofar as through it and in it a being has
[the act of] being.
-Quiddity comes from quid est, what-it-is
-Essence is the term used to translate Aristotle’s to ti en einai, the what-it-was-to-be (also
sometimes rendered in Latin as quod quid erat esse)
-form and nature are other terms that can signify what is signified by the term quiddity, but
they do so with different connotations
The quiddity or essence that is grasped by the act of apprehension is expressed through a
definition: that is, a definition is the sign of what is grasped in the act of apprehension, just as a
single word is a sign of something understood. Unlike a single word, a definition is complex in the
sense that it is composed of several words: nevertheless, a definition is simple in the sense that it
expresses one apprehended quiddity. So, for example, one expresses what one grasps in the
apprehension of the quiddity of a triangle through the definition, “three sided planar figure.” In
apprehending a quiddity, one knows a thing as it is distinct from other things, and this is why
knowledge of a quiddity is expressed through a definition, which takes the typical form of a genus
and difference.1
The apprehension of a given quiddity can be more or less distinct, as for example one
might know a horse or a dog only as an animal rather than as distinct from other animals. St.
Thomas observes that in such a case, one knows the quiddity “animal” less distinctly too, because
one knows a universal whole more distinctly when one knows its parts, i.e., the species contained
within it (ST 1.85.3):
Manifestum est autem quod cognoscere aliquid in
quo plura continentur, sine hoc quod habeatur
propria notitia uniuscuiusque eorum quae
continentur in illo, est cognoscere aliquid sub
confusione quadam. . . . Cognoscere autem
distincte id quod continetur in toto universali, est
habere cognitionem de re minus communi. Sicut
cognoscere animal indistincte, est cognoscere
animal inquantum est animal, cognoscere autem
But it is manifest that to know something in which
many things are contained, without having a proper
knowledge of each of those things which are
contained in it, is to know something under a
certain confusion. . . . But to know distinctly that
which is contained in a universal whole is to have
knowledge of a less common thing. Just as to know
animal indistinctly is to know animal insofar as it
is animal; but to know animal distinctly is to know
1SCG 3.46: “But through knowing about a thing what it is, the thing is known just as it is distinct from other
things: therefore also a definition, which signifies what a thing is, distinguishes the definitum from all
other things.” [“Per hoc autem quod scitur de re quid est, scitur res prout est ab aliis distincta: unde et
definitio, quae significat quid est res, distinguit definitum ab omnibus aliis.”]
Carl: Metaphysics 5
animal distincte, est cognoscere animal inquantum
est animal rationale vel irrationale, quod est
cognoscere hominem vel leonem. Prius igitur
occurrit intellectui nostro cognoscere animal quam
cognoscere hominem, et eadem ratio est si
comparemus quodcumque magis universale ad
minus universale.
animal insofar as it is rational or irrational animal,
which is to know man or lion: therefore it first
happens to our intellect to know animal before it
knows man: and it will be the same if we compare
whatever is more universal to what is less
universal.
In general, human knowledge proceeds from the more universal to the less universal: one
distinguishes animal before one distinguishes particular species of animal.2 There is thus progress
in one’s apprehension of any given quiddity, as one proceeds from a more universal and confused
grasp of that quiddity to a clearer knowledge of that quiddity as it is distinct from others.
Judgment
By the act of judgment—also called composition and division—the human intellect
combines and separates the indivisible intelligibles known through the act of apprehension. For
example, the judgment that the dog is white involves both the quiddity “dog” (a substance) and the
quiddity “white” (a quality). Judgment as an act thus depends upon the act of apprehension: one
cannot judge that something is such and such without some apprehensive grasp of the parts of the
judgment. In this instance, as in others, what is complex must be reduced to what is simple.
According to Aristotle, truth and falsity arise only in judgment, rather than in the
apprehension of indivisibles. By apprehension, one only knows what something is, and to fail to
know what something is is to be in a state of ignorance rather than falsity. But when one judges
that something is the case, then there can be truth or falsity about one’s intellectual act.3
In addition to the quiddities that are linked or divided in a judgment, there is the verb
copula itself—is or is not—which expresses the very composition or division of the judgment. In
speech, the most common use of the verb to be is in order to express the intellectual act of
judgment. This provides an important clue concerning the answer to our question about how it is
that the intellect knows being: we will now examine an answer to this question.
1.2. The Knowledge of Being (or Existence)
Given the distinction between apprehension and judgment as operations of the human
intellect, the question arises whether the human intellect knows being through the former or the
latter. As indicated above, the apprehension of a thing’s quiddity can be more or less distinct,
according to a greater or lesser degree of universality. A dog can be understood more generally as
an animal, or as a living thing, or as a body, or as a substance. These levels of increasingly greater
universality about the knowledge of one being, a dog, might suggest that the knowledge of being is
itself acquired through apprehension: according to this suggestion, being would be the most
general quiddity or essence, a most general universal under which all the objects known by the
human intellect would fall.
2See Physics 1.1: “Similarly a child begins by calling all men ‘father,’ and all women ‘mother,’ but later on
distinguishes each of them.”
3This will be explored in greater depth in our treatment of truth (during our study of the transcendentals) later
in the semester.
Carl: Metaphysics 6
However, there is a problem with this suggestion that being is simply the most universal
object of the act of apprehension. As we will explain below (among other places, in discussion of
the analogical character of being), it cannot be the case that being is a genus.4 But if being cannot
be a genus, then it cannot be the case that one arrives at one’s knowledge of being just through the
kind of abstraction involved in the act of apprehension. How then does a human being know
being?
To prepare for our consideration of this question, it will be helpful to briefly consider some
of the Latin terminology used by St. Thomas. Several different Latin terms associated with the
verb esse, which might all be translated into English as ‘being,’ have subtly distinct meanings in the
Latin. In this instance, an awareness of the Latin terminology serves to enrich understanding in a
crucial way. Therefore, throughout this course I will make frequent reference to these terms in the
Latin. It should be noted that even in this first section of the notes, the term being has already been
used in ways that are distinguished in Latin.
esse – the infinitive, “to be”; can be translated as being, the act of being, or existence
ens – the present participle of esse; typically used to refer to a concrete being
essentia – almost exclusively translated as essence, although sometimes as being
St. Thomas’s answer to the question raised is that it is through the intellect’s second act that
being, in the sense of a thing’s actual existence, is known. Or, to put it in another way, it is through
the intellect’s second act that there is a grasp of real being: the judgment expressed as “the thing is”
is the expression of the mind’s grasp of the real being of the thing. St. Thomas sets forth this view
in a number of texts. For example, in DT, 5.3, he begins by stating the distinction between
apprehension and judgment, the intellect’s first and second operations:
Sciendum est igitur quod secundum philosophum
in III de anima duplex est operatio intellectus. Una,
quae dicitur intelligentia indivisibilium, qua
cognoscit de unoquoque, quid est. Alia vero, qua
componit et dividit, scilicet enuntiationem
affirmativam vel negativam formando.
Et hae quidem duae operationes duobus, quae sunt
in rebus, respondent. Prima quidem operatio
respicit ipsam naturam rei, secundum quam res
intellecta aliquem gradum in entibus obtinet, sive
sit res completa, ut totum aliquod, sive res
incompleta, ut pars vel accidens. Secunda vero
We must realize, therefore, that as the Philosopher
says (De anima III) the operation of the intellect is
twofold: one, which is called the “understanding of
indivisibles,” by which it knows what a thing is.
But another, by which it composes and divides,
that is, by forming affirmative and negative
statements.
And these two operations correspond to two
[principles] in things. The first operation concerns
the nature of a thing, in virtue of which the thing
understood holds a certain rank among beings,
whether it be a complete thing, like some whole, or
an incomplete thing, like a part or an accident. But
4As will be discussed below, the reason for this is that any genus must be divided by differences taken from
outside the genus. If being were a genus, therefore, it would need to be divided by differences taken from
outside of being: but this is impossible, because whatever would be outside the genus of being would be
non-being, which is nothing.
Carl: Metaphysics 7
operatio respicit ipsum esse rei, quod quidem
resultat ex congregatione principiorum rei in
compositis vel ipsam simplicem naturam rei
concomitatur, ut in substantiis simplicibus.
the second operation concerns the very being of a
thing, which results from the union of the
principles of a thing in composite [substances], or
accompanies the thing’s simple nature, as in simple
substances.
The crucial claim here is that it is the intellect’s second operation that concerns the very
being of a thing: secunda operatio respicit ipsum esse rei. How should we understand this claim?
We need to consult a text in which St. Thomas comments on the meaning of the term esse. In In
Sent. 1.33.1.1 ad 1, St. Thomas explains that the term esse can be understood in three ways:
Sed sciendum, quod esse dicitur tripliciter. Uno
modo dicitur esse ipsa quidditas vel natura rei,
sicut dicitur quod definitio est oratio significans
quid est esse; definitio enim quidditatem rei
significat. Alio modo dicitur esse ipse actus
essentiae; sicut vivere, quod est esse viventibus,
est animae actus; non actus secundus, qui est
operatio, sed actus primus. Tertio modo dicitur
esse quod significat veritatem compositionis in
propositionibus, secundum quod “est” dicitur
copula: et secundum hoc est in intellectu
componente et dividente quantum ad sui
complementum; sed fundatur in esse rei, quod est
actus essentiae, sicut supra de veritate dictum est.
But it must be known that esse is said in three
ways. In one way esse expresses the very quiddity
or nature of a thing, as it is said that a definition is
an expression signifying what a being (esse) is; for
a definition signifies the quiddity of a thing. In
another way esse expresses the very act of an
essence; such as “to live,” which is esse in living
things, is the act of the soul; not second act, which
is operation, but first act. In a third way esse is said
as what signifies the truth of composition in
propositions, according to which “is” is called the
copula; and in this sense [esse] with regard to its
completion is in the intellect composing and
dividing; but this [esse in the mind] is founded
upon the esse of a thing, which is the act of an
essence, as was said above about truth.
Esse can mean:
(1) the quiddity of a thing
(2) the act of an essence
(3) the truth of composition as expressed in a proposition by the copula, “is”
So, in the text from the De Trinitate, when St. Thomas says that the intellect’s second
operation concerns the very esse of a thing, in which of these three senses should ipsum esse rei be
taken? It is evident by that by this St. Thomas does not mean a thing’s quiddity, because he has just
clarified that the quiddity of a thing is known by the intellect’s first operation. But he also cannot
mean by esse the truth of composition, because esse in this sense is in the intellect rather than in
things. Furthermore, as St. Thomas indicates in this text from the Sentences Commentary, esse in
the third sense is founded upon esse in the second sense, the act of an essence.
Carl: Metaphysics 8
Thus, by ipsum esse rei, St. Thomas must mean what he has called the act of an essence.
But what is it for an essence to be actual? This is just for it to be, in the sense of existence. It is for
this reason that many recent Thomistic scholars understand the ipsum esse rei that is grasped by the
mind’s second operation to be the existence of the thing.5
We can further clarify this claim, that judgment concerns the esse of a thing, by noting that
there are two kinds of judgments: (1) judgments of attribution and (2) judgments of existence.6 The
example of judgment given earlier—the dog is white—is an example of the former, in which
something is predicated of (or divided from) a subject through the verb copula. But one can also
form the judgment the dog is, that is, the dog exists. This is a judgment of existence, in which
nothing other than the actual existence of the subject is expressed. That a judgment of existence is
possible should serve as an indication that esse in the sense of existence is grasped through the
second operation of the mind.7
Resolution/Analysis and the Apprehensive Grasp of Being
Complementing this text from the Super Boetium De Trinitate 5.3, in many other places St.
Thomas speaks of the knowledge of being (ens) in terms of apprehension, frequently citing
Avicenna, as in the following example from DV 21.4 ad 4:
Cuius ratio est, quia illud quod primo cadit in
apprehensione intellectus, est ens. . . .
The reason for this is because that which first falls
into the apprehension of the intellect is being. . . .
It should be noted that Thomas cites this same principle early in the Super Boetium De
Trinitate itself (DT 1.3 obj. 3), so that it should not in itself be interpreted as contradicting what has
been said about the role of judgment in knowing being in the sense of esse. Just what does St.
Thomas means by this primacy of being (ens) in the order of apprehension? We can turn to another
text in which Thomas cites this Avicennian axiom (ST 1-2.94.2):
In his autem quae in apprehensione omnium
cadunt, quidam ordo invenitur. Nam illud quod
primo cadit in apprehensione, est ens, cuius
intellectus includitur in omnibus quaecumque quis
apprehendit. Et ideo primum principium
indemonstrabile est quod non est simul affirmare et
negare, quod fundatur supra rationem entis et non
entis, et super hoc principio omnia alia fundantur,
ut dicitur in IV Metaph.
But among those things that fall under the
apprehension of all [men], a certain order is found.
For that which first falls into the apprehension is
being, the understanding of which is included in
everything whatsoever that someone apprehends.
And therefore the first indemonstrable principle is
that there is not simultaneous affirmation and
negation, which is founded upon the meaning of
being and non-being; and upon this principle are
founded all the other [principles], as is said in
Metaphysics IV. (ST 1-2.94.2)
5For example, this is the position of Gilson, Fabro, Owens, and Wippel, and their various followers.
6For St. Thomas’s acknowledgment of this distinction, see In Per. 2.2.
7As we will see later in the course, a judgment of attribution also grasps the esse of the thing, according to its
composite character. St. Thomas claims that truth obtains in the intellect’s second operation because
Carl: Metaphysics 9
Here St. Thomas relates the primacy of the principle of non-contradiction to the primacy of
the apprehension of being (ens). What does this text mean by the primacy of the apprehension of
being? Does this not contradict the claim made in DT 5.3 that it is the intellect’s second operation
that grasps ipsum esse rei? To answer this question, we need to do two things: (1) give an account
of the relationship between the terms ens and esse, and (2) briefly discuss the notion of resolution
or analysis (resolutio).
(1) Regarding ens and esse: St. Thomas typically uses the term ens to refer to a being (in
the sense of a concrete being), and he with some frequency clarifies or explains the notion of ens as
id quod est (that which is) or habens esse (something having existence) or quod habet esse (what
has existence).8 It can be said that ens taken in this sense is the most indistinct and universal way in
which any existing thing can be apprehended. That is, it is always possible to apprehend a given
thing as a being (ens)—but it should be noted that one’s grasp of any existing thing known through
sense experience will always have some quidditative content more specific than “being.” In other
words, it will never the case that one can only say (about a given concrete thing known through
sense experience) that it is a being (ens).
However, this apprehensive grasp of ens depends upon the prior grasp of esse through the
intellect’s second operation: this is why the notion of ens is rightly explained as quod habet esse.
The concept of ens can therefore be called a complex concept, insofar as the apprehension of ens
depends upon the intellect’s grasp of esse through its second operation.
(2) Regarding the notion of resolution: whatever is complex and posterior must, according
to St. Thomas, be resolved into that which is simple and prior. Resolutio is the intellectual process
according to which one moves from the posterior to the prior. It is for this reason that it is often
translated into English as analysis. Insofar as the whole project of Aristotelian science is to proceed
from that which is posterior and better known to us to that which is prior and more knowable in
itself, science itself can be characterized as a project of resolution.
St. Thomas distinguishes resolution into two kinds: (a) resolution secundum rem and (b)
resolution secundum rationem. As Msgr. Wippel explains, according to the former kind of
resolution one seeks the extrinsic causes of a given thing; while according to the latter kind of
resolution one examines the intrinsic causes (particularly the formal cause) of the thing, proceeding
from the less universal to the more universal. It is therefore in the order of resolution secundum
rationem that one arrives at being (ens) as the most universal concept according to which a given
thing may be understood.
When it is said that something is first or prior, one must always ask the following question:
Is this priority in time, or in causality, or in the order of resolution, or in some other way? That is,
just because something is said to be first or to be before something else, this does not mean that it
is first temporally or even causally. In the case of the Avicennian axiom that being is what first falls
into the apprehension of the intellect, the “first” here should not be interpreted in a strictly
temporal way; rather, as Msgr. Wippel argues, St. Thomas seems to be referring to priority in the
order of resolution. Being (ens) is that into which whatever the intellect conceives can be resolved.
8See Wippel 33 n. 35 for a selection of references.
Carl: Metaphysics 10
2. Separatio and the Discovery of Being as Being
What we have established up to this point is that, for St. Thomas, esse in the sense of
existence is grasped through the second operation of the intellect. This grasp of esse through
judgment is attained by virtually all human beings: anyone who can understand the meaning of a
proposition of the form “x exists” grasps esse in the sense of actual existence. We have said before
that metaphysics is the science that studies being as being: is esse in the sense of existence—or,
alternatively, ens as that which is—what we mean by this expression, “being as being?”
2.1. The Distinction of the Subject of a Speculative Science: Division of the Sciences
To answer this question, we need to consider the character of the subject of a speculative
science. Every science studies being, because whatever can be known by the human intellect is
always a being.9 The subject of each of the chief speculative sciences (physics, mathematics, and
metaphysics) is distinguished by the mind as a general object of speculation. “Being” taken
generally is not in any way a distinct object of speculation, because every object of human
speculation is a being. Whether one studies dogs, triangles, or words—distinct objects of
speculation—whatever one studies must be a being. So it cannot be that being, either in the sense
of existence (esse) or in the sense of that which is (ens), is the precise subject of metaphysics.
How are the subjects of the chief speculative sciences distinguished? St. Thomas explains
in Super Boetium De Trinitate 5.1 that “the speculative sciences must be divided according to
differences between objects of speculation, considered precisely as such.”10 Now, whenever the
intellect knows an object of speculation, it does so by virtue of an immaterial likeness of the
known existing in the intellect: fundamentally, the activity of intellectual cognition is immaterial in
character.11 This leads St. Thomas to observe that an object of speculation “considered precisely as
such” is separate from matter and motion; and thus the differences among objects of human
speculation will be established by the differing degrees according to which those objects are
separate from matter and motion.
St. Thomas therefore characterizes the distinction among the objects of the chief
speculative sciences in the following way:
science object’s degree of separation from matter
physics can neither exist without matter nor be understood without matter
mathematics can not exist without matter, but can be understood without matter
metaphysics can exist without matter
The objects studied by philosophical physics (i.e., natural philosophy) can neither exist
without matter nor be understood without matter. For example, it pertains to natural philosophy to
study human nature, and: (1) human beings do not exist except in matter, and (2) one does not
understand what a human being is without knowing that a human being has flesh and bones, i.e.,
particular kinds of matter. As a science, natural philosophy does abstract from particular matter (for
example, this flesh and these bones) but not from matter taken universally. It is for this reason that
9The philosophical thesis positing the connection between being and intelligibility can be traced through
Plato to Parmenides. It is a position generally taken for granted by Aristotle.
10In DT 5.1 [Leon. 50.138]: “. . . et ideo oportet scientias speculativas dividi per differentias speculabilium in
quantum speculabilia sunt.”
11This will be a claim familiar to students who have taken courses in the Thomistic philosophy of human
nature or in Thomistic epistemology.
Carl: Metaphysics 11
St. Thomas characterizes the degree of abstraction peculiar to natural philosophy as the abstraction
of the universal from the particular rather than as the abstraction of form from matter.
By contrast, mathematics studies objects that cannot exist without matter, even though they
can be understood without matter. For example, extension (continuous quantity) or a triangle
(which is a shape, a quality) can only actually exist in a material substrate. Nevertheless, one’s
study of such mathematical objects need not make any reference to matter: in other words,
mathematics as a study makes no reference to material causes. Mathematical objects are abstracted
in this way just because they do not exist only in a particular kind of matter: for example, a triangle
can be made of bronze or of wood, without any difference in its properties qua triangle. Because of
the more abstract character of mathematical objects, St. Thomas characterizes this degree of
abstraction as the abstraction of form from matter.
The objects studied in metaphysics are separate from matter to a greater degree, in that
they are capable of existing without matter. St. Thomas lists among the objects studied by
metaphysics such examples as substance, quality, act, potency, one and many. The objects studied
by metaphysics are immaterial in this precise sense: they need not exist in matter. For this reason
the objects studied by metaphysics can be said to be negatively or neutrally immaterial, as opposed
to what is positively immaterial (as for example angels or God).12
2.2. Separatio and the Discovery of the Subject of Metaphysics
From what has been said, it is clear that esse taken in the sense of actual existence is not
the subject of metaphysics. A person can grasp the notion of existence without grasping being as
something that does not depend upon motion and matter: but it is being understood in just this
latter way that is the subject of metaphysics. How then is the subject of metaphysics known? The
objects of physics are known by abstraction of the universal from the particular; the objects of
mathematics are known by the abstraction of form from matter. What of the subject of
metaphysics?
According to St. Thomas, being as being is not known through just any judgment, but
rather through a special kind of judgment which he terms separation (separatio). In this section of
our course, we will examine his comments concerning this judgment. This will effectively be an
extended commentary on the closing section of the In DT 5.3. (I am providing Fr. Armand Maurer’s
translation of this key text.)
Sic ergo intellectus distinguit unum ab altero aliter
et aliter secundum diversas operationes; quia
secundum operationem, qua componit et dividit,
distinguit unum ab alio per hoc quod intelligit
unum alii non inesse. In operatione vero qua
intelligit, quid est unumquodque, distinguit unum
ab alio, dum intelligit, quid est hoc, nihil
intelligendo de alio, neque quod sit cum eo, neque
quod sit ab eo separatum. Unde ista distinctio non
Accordingly, through its various operations the
intellect distinguishes one thing from another in
different ways. Through the operation by which it
composes and divides, it distinguishes one thing
from another by understanding that the one does
not exist in the other. Through the operation,
however, by which it understands what a thing is, it
distinguishes one thing from another by knowing
what one is without knowing anything of the other,
12This is the language used by Msgr. Wippel. See Wippel 44.
Carl: Metaphysics 12
proprie habet nomen separationis, sed prima
tantum. Haec autem distinctio recte dicitur
abstractio, sed tunc tantum quando ea, quorum
unum sine altero intelligitur, sunt simul secundum
rem.
either that it is united to it or separated from it. So
this distinction is not properly called separation,
but only the first. It is correctly called abstraction,
but only when the objects, one of which is known
without the other, are one in reality.
Separation is the act by which one understands “that one does not exist in the other.” It
therefore differs from abstraction, properly speaking, because abstraction always involves the
mental separation of things that are one in reality (such as the universal and the particular, or form
and matter). While abstraction in this strict sense13 is according to the intellect’s first operation
(because to name a universal abstracted from the particular or a form abstracted from matter is to
state what something is), separation in the strict sense delineated here is according to the intellect’s
second operation, which is judgment. St. Thomas elaborates on this claim about separation as
opposed to abstraction later in q. 5 a. 3:
In his autem quae secundum esse possunt esse
divisa, magis habet locum separatio quam
abstractio. Similiter autem cum dicimus formam
abstrahi a materia, non intelligitur de forma
substantiali, quia forma substantialis et materia sibi
correspondens dependent ad invicem, ut unum sine
alio non possit intelligi, eo quod proprius actus in
propria materia fit. Sed intelligitur de forma
accidentali, quae est quantitas et figura, a qua
quidem materia sensibilis per intellectum abstrahi
non potest, cum qualitates sensibiles non possint
intelligi non praeintellecta quantitate, sicut patet in
superficie et colore, nec etiam potest intelligi esse
subiectum motus, quod non intelligitur quantum.
Substantia autem, quae est materia intelligibilis
quantitatis, potest esse sine quantitate; unde
considerare substantiam sine quantitate magis
pertinet ad genus separationis quam abstractionis.
But in the case of things that can exist separately,
separation rather than abstraction obtains.
Similarly, when we say form is abstracted from
matter, we do not mean substantial form, because
substantial form and the matter correlative to it are
interdependent, so that one is not intelligible
without the other, because the appropriate act is in
its appropriate matter. Rather, we mean the
accidental forms of quantity and figure, from
which indeed sensible matter cannot be abstracted
by the intellect, because sensible qualities cannot
be understood unless quantity is presupposed, as is
clear in the case of surface and color. And neither
can we understand something to be the subject of
motion unless we understand it to possess quantity.
Substance, however, which is the intelligible
matter of quantity, can exist without quantity.
Consequently, the consideration of substance
without quantity belongs to the order of separation
rather than to that of abstraction.
13I add the qualification “in the strict sense” here because at times St. Thomas uses the term abstraction more
generally so as to include both abstraction in the strict sense (which is according to the intellect’s first
operation) and separation (which is according to the intellect’s second operation).
Carl: Metaphysics 13
St. Thomas begins by discussing the abstraction of mathematical objects. He notes that
when it is said that one abstracts form from matter, this does not mean that one abstracts the
substantial form from matter—such an abstraction is not possible, because a corporeal substance is
not intelligible apart from its appropriate matter. Rather, what one abstracts in mathematics are
quantities and figures (a kind of quality), which do not depend upon a particular kind of matter for
their existence. (That is, they can exist in bronze, in wood, etc., which are different kinds of
substance.)
These quantitative and qualitative forms are therefore abstracted from what St. Thomas
calls sensible matter, by which he means material things insofar as they are known through their
sensible qualities. It is possible to abstract quantity and figure from sensible matter because the
latter presupposes the former for its very intelligibility: for example, one cannot understand color
(a sensible quality) without knowing that it is an accident of a surface. However, one does not
abstract quantity or figure from matter absolutely, because quantity and figure are always accidents
of a substance. By the phrase intelligible matter, St. Thomas means the matter that “exists in
sensible things, but not insofar as they are sensible.”14 Intelligible matter is grasped only by the
intellect, which grasps substance as what underlies all accidents. When one abstracts mathematical
objects (such as a triangle), one does not abstract from matter absolutely, but only from sensible
matter.
Thus, although quantity cannot exist without an underlying substance15, substance can
exist without quantity. However, one does not recognize this truth by virtue of any abstraction by
the intellect. Rather, it is by virtue of what St. Thomas above called separation—an instance of the
intellect’s second operation—that one judges that substance is not of itself quantified. To consider
substance in this way, as without quantity, “belongs to the order of separation rather than to that of
abstraction.”
Sic ergo in operatione intellectus triplex distinctio
invenitur. Una secundum operationem intellectus
componentis et dividentis, quae separatio dicitur
proprie; et haec competit scientiae divinae sive
metaphysicae. Alia secundum operationem, qua
formantur quiditates rerum, quae est abstractio
formae a materia sensibili; et haec competit
mathematicae. Tertia secundum eandem
operationem quae est abstractio universalis a
particulari; et haec competit etiam physicae et est
communis omnibus scientiis, quia in scientia
praetermittitur quod per accidens est et accipitur
quod per se est. Et quia quidam non intellexerunt
differentiam duarum ultimarum a prima, inciderunt
We conclude that there are three kinds of
distinction in the operation of the intellect. There is
one through the operation of the intellect joining
and dividing which is properly called separation;
and this belongs to divine science or metaphysics.
There is another through the operation by which
the quiddities of things are conceived which is the
abstraction of form from sensible matter; and this
belongs to mathematics. And there is a third
through the same operation which is the
abstraction of a universal from a particular; and
this belongs to physics and to all the sciences in
general, because science disregards accidental
features and treats of necessary matters. And
14In Metaphysicorum Bk. 7 lec. 10, no. 1496.
15Except by the power of God, as in the Eucharistic species.
Carl: Metaphysics 14
in errorem, ut ponerent mathematica et universalia
a sensibilibus separata, ut Pythagorici et Platonici.
because certain men (for example, the
Pythagoreans and the Platonists) did not
understand the difference between the last two
kinds of distinction and the first, they fell into
error, asserting that the objects of mathematics and
universals exist separate from sensible things.
Here St. Thomas draws his conclusion, associating the two kinds of abstraction with
mathematics and physics and separation with metaphysics, which is also called the divine science.
The objects studied by metaphysics are not abstracted in the strict sense, but are distinguished
through the judgment of separation, in which one negatively judges that being (substance, act,
potency etc.) need not be quantified or material.
The prerequisites for separation
By a careful reading of In DT 5.3, we have established that the objects studied by
metaphysics are grasped by the mind not through abstraction but through a special form of
judgment called separation. In this famous text, however, St. Thomas leaves untreated the question
of how one comes to make the judgment of separation. Among Thomists in the 20th century, the
question of the prerequisites necessary for making the judgment of separation was a source of
significant disagreement. We will sketch here two rival positions.
(1) The River Forest Thomists hold that in order to make the judgment of separation and
begin metaphysics, one must first demonstrate by philosophical argument that positively
immaterial being exists. This can be accomplished by establishing the existence of an immaterial
first cause of motion (as Aristotle establishes in the Physics) or perhaps by proof of the
immateriality of the human soul (as Aristotle takes up in the De Anima). In general, therefore, the
River Forest position is that the study of natural philosophy is not only pedagogically preparatory
for metaphysics, but that it is in fact strictly necessary: on this view, one cannot reasonably study
metaphysics until one knows that positively immaterial being exists, by virtue of previous
philosophical study.
(2) The view favored by authors such as Gilson, Klubertanz, Owens, and Wippel is instead
that one can be in a position to make the judgment of separation without having demonstrated the
existence of the positively immaterial. For example, Msgr. Wippel contends that one already makes
the judgment of separation when one recognizes that a given physical being can be examined
insofar as it is living, or insofar as it is mobile, or insofar as it is material, or simply insofar as it is
a being. That is, what the judgment of separation entails is just that a given being—something that
exists—can be examined just insofar as it is a being, rather than insofar as it is a particular kind of
being. On Msgr. Wippel’s view, St. Thomas’s point in In DT 5.3 is just that the kind of distinction
involved in taking up this perspective—seeing a being qua being—belongs to the order of
separation rather than to the order of abstraction.
It is not my intention to attempt at this point to settle this dispute between River Forest
Thomism and the position generally favored among those, for other reasons, often called
“existential” Thomists, although on this question my opinion tends to favor the latter view. I agree
with Msgr. Wippel that a demonstration in natural philosophy can provide the basis upon which
Carl: Metaphysics 15
one makes the judgment of separation.16 The question is whether or not such a demonstration is the
only way to ground the judgment of separation. However one settles this question about the
prerequisites necessary for the act of separation, it can be held that what this judgment establishes
is that being can be examined simply insofar as it is being. This is what St. Thomas says is the
subject matter of metaphysics.
This being said, in my view, it is possible to begin the project of metaphysics without
having demonstrated the existence of positively immaterial being. That is, one can do just what
Msgr. Wippel claims, which is to consider a being simply insofar as it is a being, even if one has
never demonstrated the existence of the positively immaterial. If one insists that what St. Thomas
calls the judgment of separation can only be justified by a demonstration of the existence of the
positively immaterial, then in my view one could also reasonably conclude that the judgment of
separation is not what establishes the subject of metaphysics; rather, it is a judgment that belongs
to the order of metaphysics.
2.3. Being as Being as the Subject of Metaphysics
The meaning of being as being
As stated above, the subject of metaphysics is being as being or being in general (ens
commune). In his Metaphysics, Aristotle distinguishes the various ways in which being can be
understood in order to clarify the notion of being as being. In Metaphysics 5.7, Aristotle first
distinguishes between accidental being and essential being; he then subdivides essential being into
being in the categories, being as true, and being as actual and potential. I will present these
distinctions as St. Thomas characterizes them in his Commentary on the Metaphysics.
(1) By accidental being (ens per accidens), Aristotle does not mean the being of an
accident, for example the quality white or the relation paternity. Rather, accidental being is that to
which one refers when one predicates something accidentally. For example, that a man is white is
accidental, because it does not belong to the essence of man to be white. The “being” that is
accidental here is what is signified by the underlined is. Aristotle holds that the causes of accidental
being are themselves accidental, such that there cannot be science about this kind of being, since
science is knowledge about the necessary through essential causes.
Essential being (ens per se) is then divided as follows:
(2) Being in the ten categories (or predicaments): St. Thomas calls this being outside the
mind (ens extra animam) and complete being (ens perfectum). Substances and the nine kinds of
accidents are all instances of ens per se, and indeed this is the most important division of essential
being. We will say more about being in the categories in a moment.
(3) Being as true: this is the being of a proposition as composed by the mind. For example,
if I form the judgment that “the apple is red,” this proposition insofar as it is a product of the mind
has being in the mind. St. Thomas explains that it is also the only way in which such things as
privations and negations have being. For example, one can judge that “the dog is blind,” but
blindness is not a real accident of the dog; blindness is rather just the privation of the exercise of
the power of sight in the dog, which is a being that should normally be able to exercise this power.
For this reason being as true is also often referred to as being in the mind.
Being in the categories is then divided as follows:
(4) Being as actual and potential: being in the categories can itself be subdivided in this
16See Wippel 61-62.
Carl: Metaphysics 16
way, into the actual and the potential. For example, a seed is potentially a tree (a substance), and
pale skin is potentially tan (a quality). It is important to note that potential being is an instance of
ens per se extra animam, essential being outside the mind. That is, potential being is not just an
instance of being in the mind, the way that a privation is a being in the mind.17
Of the above divisions of being, Aristotle excludes both accidental being and being as true
from consideration as the subject-matter of metaphysics: these are not being as being or ens
commune as it is studied by metaphysics. This leaves being in the categories, which is further
subdivided into actual and potential being, as the subject-matter of metaphysics. By ens commune
therefore we mean being in the categories, both actual and potential.
God and the subject of metaphysics
In addition to the assertion that metaphysics studies being as being, Aristotle also considers
the possibility that metaphysics studies the highest or best instances of being—these are, for
Aristotle, the separate substances. Aristotle’s attempt at a solution to this question is still a matter of
considerable controversy in scholarly discussions today; what concerns us here is how St. Thomas
answers this question. How is the subject of metaphysics related to the highest being, that is, God?
We can profitably consider St. Thomas’s position on this question in relation to the answers given
previously by the Muslim philosophers Avicenna and Averroes.
Avicenna contends that God (the highest separate substance) is not the subject of
metaphysics, but rather being as being is this science’s subject.18 For Avicenna, metaphysics proves
the existence of God, identifying Him as the first and necessary cause of contingent being. By
contrast, Averroes holds that God’s existence is not established by metaphysics, but rather by
physics (or natural philosophy). According to this latter view, God is the subject of metaphysics as
the first and primary instance of substance: it is because metaphysics studies being as being (which
Averroes takes as primarily meaning substance) that it must study the highest substance in
particular, i.e., God.19
Understanding the positions of Avicenna and Averroes in this way, St. Thomas clearly sides
with the former: St. Thomas contends that the subject-matter of metaphysics is being as being (ens
inquantum est ens) or what he will call being in general (ens commune). Metaphysics primarily
concerns itself with the study of everything that is common to every being, as opposed to the study
of the features that belong only to this or that kind of being. Although God is not the subject of
metaphysics for St. Thomas, nevertheless God is considered by metaphysics—not as its subject,
but as the first cause of being. In other words, metaphysics has as its subject what was termed
above the negative or neutrally immaterial—what is common to all beings—but ultimately
identifies as the cause of its subject what is positively immaterial (God and the separate
substances).
Finally, as we shall explain again and in greater detail later, it is crucially important to note
that God is not a part of the subject of metaphysics: He does not fall under what we will call ens
commune.
17This is a key to Aristotle’s response to the dilemma of Parmenides, who asserted a distinction between
being and non-being that would not allow for the possibility of change. Accepting potential being as real
being serves to defuse this aspect of the Parmenidean dilemma.
18See Wippel 13.
19See Wippel 13-14.
Carl: Metaphysics 17
4. Analogy I: the “Horizontal” Analogy of the Categories
It has become common among contemporary Thomists, following the presentation of
Cornelio Fabro, to distinguish two different levels according to which one can discuss analogy, and
in particular the analogical character of being. We will begin with the notion of analogy that
pertains to ens commune considered in itself; this can be distinguished from the analogy that
obtains between creatures and God.20
4.1. The Notion of Analogy
Univocity and equivocity
To understand the notion of analogy, we must first distinguish between univocity and
equivocity, which are the two basic different ways in which a given term or concept can be related
to two distinct realities. Aristotle draws the distinction between univocal and equivocal terms at the
beginning of his Categories.
A term is used univocally when it is used to name two things, with the same meaning or
definition in each case. For example, when I say that I am a man and that Fr. James is a man, the
term man is used univocally: in each instance that the term is used, it means precisely the same
thing.
By contrast, a term is used equivocally when it is used to name two things, with a different
meaning or definition in each case. For example, bank can refer both to a place where money is
deposited for safe-keeping and the boundary of a river.
Now, according to Aristotle, it cannot be the case that being is a univocal term when it is
taken to refer to substances and to accidents.
Pros hen equivocation
Aristotle distinguishes a third way in which a term can be used, which he calls pros hen
(towards one) equivocation. Strictly speaking, pros hen equivocation is a species of equivocation,
because the same term is used to name two things according to different meanings or definitions.
However, unlike the purely equivocal use of bank or pen to name totally unrelated things, some
terms are used equivocally to name things that are different but closely related to each other.
Aristotle’s most famous example of this kind of equivocation is the term healthy. Consider
the following examples:
(1) The man is healthy.
(2) Exercise is healthy.
(3) Salad is healthy.
(4) The urine is healthy.
The term healthy is used to describe these four things. The use of the term is not univocal. For a
man to be healthy means that his body is generally in good condition, with order and good
operation of his organs. But exercise, salad, and urine do not even have bodily organs: for each of
these things to be healthy cannot be the same thing as for a man to be healthy. Rather, exercise and
salad are called healthy insofar as they are causes of health in a man; and urine is called healthy
insofar as it is a sign of health in a man. This is pros hen equivocation because the meaning of each
of the secondary analogates includes, in its definition, the primary analogate: for example, salad is
20It should be noted that most of the controversy concerning the interpretation of St. Thomas’s thought about
analogy concerns this latter analogy between creatures and God.
Carl: Metaphysics 18
healthy in that it causes the health of a man.
Analogy
Although it is not possible for us to consider at this time the historical background for St.
Thomas’ notion of analogia, we can note that the Thomistic doctrine of analogy has as its most
important precursor the Aristotelian doctrine of pros hen equivocation, but as this was treated and
developed by later Greek and Arabic commentators on Aristotle. Aristotle himself does discuss the
notion of analogia, but for him this term means what it typically means in arithmetic or geometry.
How it is, historically, that pros hen equivocation and analogia came to be intertwined notions is
beyond our present concern. It should only be noted that this historical background helps to explain
some of the developments in St. Thomas’s personal doctrine concerning analogy. However, we will
concern ourselves here only with his mature doctrine.
Just as pros hen equivocation is compared to univocation and equivocation by Aristotle, so
St. Thomas compares analogical predication to both univocal and equivocal predication. In his
early De principiis naturae, c. 6, St. Thomas characterizes these three modes of predication as
follows:
Ad huius intelligentiam sciendum est quod
tripliciter aliquid predicatur de pluribus: univoce,
equivoce et analogice. Univoce predicatur quod
predicatur secundum idem nomen et secundum
rationem eandem, id est diffinitionem, sicut animal
predicatur de homine et de asino: utrumque enim
dicitur animal, et utrumque est substantia animata
sensibilis, quod est diffinitio animalis. Equivoce
predicatur quod predicatur de aliquibus secundum
idem nomen et secundum diversam rationem, sicut
canis dicitur de latrabili et de celesti, que
conveniunt solum in nomine et non in diffinitione
sive significatione; id enim quod significatur per
nomen est diffinitio, sicut dicitur in IV
Metaphysice. Analogice dicitur predicari quod
predicatur de pluribus quorum rationes diverse
sunt, sed attribuuntur uni alicui eidem, sicut sanum
dicitur de corpore animalis et de urina et de
potione, sed non ex toto idem significat in
omnibus: dicitur enim de urina ut de signo
sanitatis, de corpore ut de subiecto, de potione ut
de causa. Sed tamen omnes iste rationes
attribuuntur uni fini, scilicet sanitati.
To understand this it must be known that
something is predicated of several things in three
ways: univocally, equivocally, and analogically.
That is predicated univocally which is predicated
according to the same name and according to the
same intelligible content, which is a definition. In
this way animal is predicated of man and of
donkey: for each is called animal, and each is an
animate sensible substance, which is the definition
of animal. That is predicated equivocally which is
predicated of several things according to the same
name and according to diverse intelligible content.
In this way dog is said of what barks and of a
heaven[ly body], which agree only in name and not
in definition or signification; for that which is
signified through a name is the definition, as is said
in Metaphysics IV. That is said to be predicated
analogically which is predicated of several things
whose intelligible contents are diverse, but are
related to one and the same thing. In this way
healthy is said of the body of an animal and of
urine and of medicine, but it does not signify
entirely the same thing in all of them: for it is said
Carl: Metaphysics 19
of urine as of the sign of health, of the body as of
[its] subject, [and] of medicine as of [its] cause.
Nevertheless all these intelligible contents are
related to one end, namely health.
Whenever something is predicated analogically, it is predicated primarily (per prius) of
one thing and secondarily (per posterius) of other things. The key to understanding St. Thomas’s
notion of analogy is that the secondary analogates are related to the primary analogate according to
some mode of causality: it is causality that provides the connection among the analogates.21 This
causality can be final causality (as it is in the example of health, where the secondary analogates
are ordered to health as an end); it can be efficient causality (as we shall see later in our treatment
of the analogy between God and created being); and it can be material or subject causality.
In commenting on Metaphysics 4.1, St. Thomas offers an important point of development:
Sed sciendum quod aliquid praedicatur de diversis
multipliciter: quandoque quidem secundum
rationem omnino eamdem, et tunc dicitur de eis
univoce praedicari, sicut animal de equo et bove.
Quandoque vero secundum rationes omnino
diversas; et tunc dicitur de eis aequivoce
praedicari, sicut canis de sidere et animali.
Quandoque vero secundum rationes quae partim
sunt diversae et partim non diversae: diversae
quidem secundum quod diversas habitudines
important, unae autem secundum quod ad unum
aliquid et idem istae diversae habitudines
referuntur; et illud dicitur “analogice praedicari,”
idest proportionaliter, prout unumquodque
secundum suam habitudinem ad illud unum
refertur.
Item sciendum quod illud unum ad quod diversae
habitudines referuntur in analogicis, est unum
numero, et non solum unum ratione, sicut est unum
illud quod per nomen univocum designatur.
But it must be known that something is predicated
of diverse [things] in several ways: sometimes
according to entirely the same intelligible content,
and then it is said to be predicated of them
univocally, as animal [is predicated] of horse and
ox. But sometimes according to intelligible
contents in every way diverse: and then it is said to
be predicated of them equivocally, as dog of a star
and of an animal. But sometimes according to
intelligible contents which are partly diverse and
partly not diverse: diverse insofar as they imply
diverse relations, but one insofar as these diverse
relations are referred to something one and the
same; and that is said “to be predicated
analogically,” that is, proportionally, as each of
them according to its own relation is referred to
that one [thing].
Furthermore it must be known that that one, to
which the diverse relations are referred among the
analogates, is one in number, and not only one in
intelligible content, as is the one which is
designated by a univocal name.
21See Wippel 77; Montagnes 26.
Carl: Metaphysics 20
In this text, St. Thomas emphasizes that the primary referent of analogical predication is
always something that is one not merely in ratio (that is, notion or intelligible content) but is also
numerically one: that is, the primary referent of analogical predication is one thing. For example,
in the case of healthy, it is the health (understand as a singular thing, a quality) of the animal that is
the primary referent in relation to which all of the secondary analogates are called healthy.
4.2. The analogy of being on the predicamental level
Although application of the notion of analogy is not restricted to being, nevertheless the
analogy of being is its most famous and most important application in the thought of St. Thomas.
The analogy of being can be formulated on two distinct levels: (1) on the “horizontal” or
predicamental level, according to which being is said analogically of accidents and of substances;
and (2) on the “vertical” or transcendental level, according to which being is said analogically of
God and creatures.22 We will treat the second level of the analogy of being later in our course; for
now, we are concerned with the analogy of being on the predicamental level.
In brief, the theory of Aristotle is that being is a pros hen equivocal term in which the
secondary analogates are the beings in the categories of accidents and the primary analogate is
being in the category of substance.23 St. Thomas holds the same view, but he articulates this claim
in terms of analogy. We will now consider, at length, St. Thomas’s commentary on Metaphysics
4.1.
Dicit ergo primo, quod ens sive quod est, dicitur
multipliciter. . . .
Et ideo dicit quod ens etsi dicatur multipliciter, non
tamen dicitur aequivoce, sed per respectum ad
unum; non quidem ad unum quod sit solum ratione
unum, sed quod est unum sicut una quaedam
natura. . . .
Sed tamen omne ens dicitur per respectum ad
unum primum. Sed hoc primum non est finis vel
efficiens sicut in praemissis exemplis, sed
subiectum. Alia enim dicuntur entia vel esse, quia
per se habent esse sicut substantiae, quae
principaliter et prius entia dicuntur. . . .
Sciendum tamen quod praedicti modi essendi ad
Therefore he says first that being (ens) or what is is
said in many ways. . . .
And therefore he says that being (ens) even if it is
said in many ways, is nevertheless not said
equivocally, but with respect to one; indeed not
[with respect] to a one that is one only in
intelligible content, but which is one as a certain
single nature. . . .
Nevertheless every being (ens) is called [being]
with respect to one first [thing]. But this first
[thing] is not an end or an efficient [cause] as in the
previous examples, but is a subject. For some
things are called beings (entia) or esse, because
they have esse in themelves, such as substances,
which are principally and primarily called beings
(entia).
Nevertheless it must be known that the
22See Wippel 73-74 for this language.
23See Metaphysics 4.1.
Carl: Metaphysics 21
quatuor possunt reduci. Nam unum eorum quod est
debilissimum, est tantum in ratione, scilicet
negatio et privatio, quam dicimus in ratione esse,
quia ratio de eis negociatur quasi de quibusdam
entibus, dum de eis affirmat vel negat aliquid.
Secundum quid autem different negatio et privatio,
infra dicetur.
Aliud autem huic proximum in debilitate est,
secundum quod generatio et corruptio et motus
entia dicuntur. Habent enim aliquid admixtum de
privatione et negatione. Nam motus est actus
imperfectus, ut dicitur tertio Physicorum.
Tertium autem dicitur quod nihil habet de non ente
admixtum, habet tamen esse debile, quia non per
se, sed in alio, sicut sunt qualitates, quantitates et
substantiae proprietates.
Quartum autem genus est quod est perfectissimum,
quod scilicet habet esse in natura absque
admixtione privationis, et habet esse firmum et
solidum, quasi per se existens, sicut sunt
substantiae. Et ad hoc sicut ad primum et
principale omnia alia referuntur. Nam qualitates et
quantitates dicuntur esse, inquantum insunt
substantiae; motus et generationes, inquantum
tendunt ad substantiam vel ad aliquid
praedictorum; privationes autem et negationes,
inquantum removent aliquid trium praedictorum.
aforementioned modes of being can be reduced to
four. For one of these which is the weakest [mode
of being], is [being] only according to reason,
namely negation and privation, which we say exist
according to reason, because [our] reason is
concerned with them as if with certain beings when
it affirms or denies something of them. But in what
way negation and privation differ will be discussed
below.
But another [mode of being] is close to [the first
mode of being] in weakness, insofar as generation
and corruption and motion are called beings
(entia). For they have something admixed with
privation and negation. For motion is the act of the
imperfect, as is said in Physics III.
But the third [mode of being] is called that which
has nothing of non-being admixed, but has weak
being, because [they have esse] not in themselves,
but in another, such as qualities, quantities, and the
properties of substance.
But the fourth kind is that which is most perfect,
which namely has esse in [its] nature without
admixture of privation, and has stable and
complete esse, existing as it were in itself, as are
substances. And to this as to the first and principal
all the others are referred. For qualities and
quantities are said to exist insofar as exist in
substances; motion and generation, insofar as they
tend to substance or to something of the [other]
mentioned [modes of being]; but privations and
negations insofar as they remove something from
the [other] three mentioned [modes of being].
Carl: Metaphysics 22
St. Thomas distinguishes here four modes of being:
(1) The being of privations and negations. -being only according to reason
(2) The being of generation, corruption, and motion. -admixed with non-being
(3) The being of accidents. -being in another
(4) The being of substance. -stable and complete being per se
It is the fourth mode of being distinguished here to which the other three modes are
ultimately referred. Beings of the first mode (privations and negations) are beings of reason, in that
a privation or negation serves to remove or deny being in one of the other three modes (rest is the
negation or privation of motion; blind is the privation of sight; non-substance is the negation of
substance). Beings of the second mode (generation, corruption, and motion) are beings insofar as
they terminate in being in the third or fourth modes—according to Aristotle and St. Thomas,
generation, corruption, and motion occur in the categories of substance, quantity, quality, and
place. Beings of the third mode are related to being of the fourth mode insofar as they exist in
substances as in their subject.
As noted above, for St. Thomas the analogical predication of a term depends upon some
causal relationship that exists among the analogates. In the case of the analogical predication of
being on the predicamental level, the causal relationship between substance and accidents is that
substance is the subject or quasi-material cause of accidents: accidents exist in substances and are
therefore dependent beings. That is, an accident is a being (a habens esse) because it inheres in a
substance, which is being in the primary sense. For this reason, being (ens) is predicated primarily
(per prius) of substance and secondarily (per posterius) of accidents, and the predication of being
as regards accidents is by relation to the category of substance.
Being is not a genus24
Because being is not a univocal term, it is not the case that being is a genus. Every generic
and specific universal term is predicated univocally of the many individuals that fall under these
universals. If being is not a univocal term, then it cannot be a generic or specific universal. Thus,
being is not a genus.25
This conclusion can also be confirmed, as Aristotle argues, by noting that every genus is
divided by differences that are taken from outside the genus.26 Therefore, if being were a genus, it
would have to be divided by non-being. But a difference is always some positive characteristic,
and therefore non-being cannot divide being as if it were a univocal genus.
Therefore, instead of saying that the ten categories are the ten species of being taken as a
genus, St. Thomas prefers to say that the ten categories are ten modes of being. St. Thomas takes it
that when something is divided into various modes, it is not divided in the same way as a genus is
divided into species. The ten categories are therefore better thought of as the ten different ways in
which things can exist extra animam, rather than as ten kinds of being.
Is being ever predicated univocally?27
Given that being is not a genus divided into the ten categories, the next question to arise is
whether being can ever be said univocally of two things that are the same in some way. For
24See Wippel 87-90.
25There are texts in which St. Thomas speaks of being as a genus—in these texts, we must conclude that the
term genus is itself being used in an analogical sense.
26See Metaphysics 998b21-27.
27See Wippel 90-93.
Carl: Metaphysics 23
example, are two members of the same genus or of the same species called beings univocally?
St. Thomas’s answer to this question can be articulated at three different levels:
(1) St. Thomas holds that different levels or grades of substance are not beings univocally;
by this he means that incorporeal substances (i.e., the angels) do not share being univocally with
corporeal substances (e.g., you and me). His reasoning for this claim is beyond what we can fully
explain at the present, but it involves his claims about the composition of esse and essence in every
created substance.
(2) Among substances of the same level or grade but of distinct species (e.g., a dog and a
man), St. Thomas holds that once again being is not predicated univocally. Again the reason for
this view is beyond our present attention.
(3) It can also be asked whether or not being is predicated univocally of two substances of
the same species (e.g., of two men). As Msgr. Wippel notes, Thomists have differed historically on
this question: John of St. Thomas rejects analogical predication of being in this case, but Msgr.
Wippel offers reasons for holding that even this predication of being will be analogical.28 If his
view on this point is correct, then it will never be the case that being is predicated univocally of
any two distinct things.
Concluding remarks concerning predicamental analogy
It should be noted that what we have called the predicamental analogy of being—the
analogy according to which being is said of both accidents and of substance—is not the only type
of analogy of being in the thought of St. Thomas, and indeed it is far less commented upon than the
other kind of analogy of being, that which obtains between created being and uncreated being. The
Aristotelian theory according to which being is said primarily of substance and secondarily of
accidents is accepted by St. Thomas in a straightforward way, with relatively little need for
extensive clarification by scholarship. What we will later call the transcendental analogy between
God and creatures requires much more careful consideration.
28See Wippel 93. The reason Msgr. Wippel offers is that St. Thomas asserts that esse understood as the act of
existing (actus essendi) is present in only one thing and is only analogically common to two things. But
since being (ens) is understood as what has being (quod habens esse), it follows that ens too can only be
analogically common even to two members of the same species.
Carl: Metaphysics 24
5. Participation
A theme in the thought of St. Thomas that has received much greater attention since the
mid-20th century is that of participation. That the notion of participation deserves sustained
attention should be clear simply from the frequency with which St. Thomas employs the language
of participation in his writings.29 Even if one should conclude that participation is not a notion that
is fundamental to St. Thomas’s metaphysical thought, still one must contend with what St. Thomas
means by the language of participation.
As we shall see, St. Thomas frequently uses the language of participation to express his
doctrine of the real composition of esse and essence in (created) beings. We have not yet addressed
any of St. Thomas’s reasoning in support of this position; for now, our purpose is only to
understand the meaning of this language of participation. Following the presentation of Msgr.
Wippel, we will begin by considering what St. Thomas means by participation in general, with a
quick consideration of St. Thomas’s attitude towards the Platonic theory of participation.
5.1. St. Thomas’s Attitude Towards Plato on Participation
The historical background for the notion of participation is primarily Platonic: one finds in
the dialogues of Plato the famous claim that individual sensible realities participate in the eternal,
immaterial Forms. In this way, Socrates is supposed to be a man by his participation in the separate
Form, man-itself. Concerning this theory, in addition to his more substantive critiques, Aristotle is
famously dismissive of the very language of participation (Metaphysics 1.6):
In his Commentary on this text, St. Thomas shifts the blame for not considering the
meaning of participation exclusively onto the Pythagoreans (In Meta. 1.10):
Hoc autem nomen participationis Plato accepit a
Pythagora. Sed tamen transmutavit ipsum.
Pythagorici enim dicebant numeros esse causas
rerum sicut Platonici ideas, et dicebant quod
huiusmodi existentia sensibilia erant quasi
quaedam imitationes numerorum. Inquantum enim
numeri qui de se positionem non habent,
accipiebant positionem, corpora causabant. Sed
quia Plato ideas posuit immutabiles ad hoc quod de
Now Plato took this name of participation from
Pythagoras. But he altered it. For the Pythagoreans
said that numbers are the causes of things, just as
the Platonists [say that] the ideas [are]; and they
said that sensible existents of this kind are certain
imitations of numbers. For insofar as numbers,
which of themselves do not have position, received
position, they caused bodies. But because Plato
held the ideas [to be] immutable in order that there
29Quick searches on the Index Thomisticus reveal that St. Thomas’s use of the language of participation is in
fact more common than his use of the (explicit) language of analogy.
For according to [Plato], it is impossible that there should be a common definition of any one of these
sensible things which are always changing. Such entities, then, he called Ideas or Forms (species); and
he said that all sensible things exist because of them and in conformity with them; for there are many
individuals of the same name because of participation in these Forms. With regard to participation, he
[merely] changed the name; for while the Pythagoreans say that things exist by imitation of numbers,
Plato says that they exist by participation, changing the name. Yet what this participation or imitation of
Forms is they commonly neglected to investigate.
Carl: Metaphysics 25
eis possent esse scientiae et definitiones, non
conveniebat et in ideis uti nomine imitationis. Sed
loco eius usus est nomine participationis. Sed
tamen est sciendum, quod Pythagorici, licet
ponerent participationem, aut imitationem, non
tamen perscrutati sunt qualiter species communis
participetur ab individuis sensibilibus, sive ab eis
imitetur, quod Platonici tradiderunt.
could be science and definitions about them, he did
not agree [with the Pythagoreans] in using the
name of imitation. But in its place he used the
name of participation. But it must be known that
the Pythagoreans, although they posited
participation or imitation, nevertheless they did not
scrutinize how a common species is participated or
imitated by sensible individuals; [but] the
Platonists did treat this.
Whereas Aristotle seems to blame Plato along with the Pythagoreans for failing to
carefully consider the meaning of participation, St. Thomas preserves the Platonists from this
criticism: even if, as we shall see, he sides with Aristotle rather than the Platonists concerning the
reality of separate Forms, and he expresses the Aristotelian position concerning the relationships
between particulars and universals in the language of participation.
5.2. The Meaning of Participation in General
St. Thomas’s most careful presentation of the meaning of participation is found in his
Commentary on the De Hebdomadibus of Boethius, lec. 2.30 He begins with an etymological
explanation of the meaning of participare:
Est autem participare quasi partem capere. Et ideo
quando aliquid particulariter recipit id quod ad
alterum pertinet universaliter, dicitur participare
illud, sicut homo dicitur participare animal quia
non habet rationem animalis secundum totam
communitatem; et eadem ratione Sortes participat
hominem.
But to participate is, as it were, to take a part. And
therefore when something receives in a particular
way that which belongs to another in a universal
way, it is said to participate that, as man is said to
participate animal since [man] does not possess the
intelligible content of animal according to [its]
entire community; and in the same way Socrates
participates man.
To participate is “to take a part” of something, to receive and possess in a particular or
partial way what belongs to something else in a universal or total way. Consequently, a species
is said to participate (in) its genus, and an individual is said to participate (in) its species (and its
various genera). When it is said that a species participates its genus and that an individual
participates a universal, in both cases we can take this to mean that the former does not exhaust the
intelligible content of the latter. For example, man is but one particular kind of animal.
Consequently, there are things belonging to animal taken as a universal whole (namely, the things
belonging to non-human animals according to their differentiating characteristics) that do not
30It is worth noting that Boethius, in general, was committed to the harmony between the thought of Plato
and the thought of Aristotle. He expresses this view early in the Consolation of Philosophy, and he
characterizes the defense of this view as a central aim of his own philosophical exertions.
Carl: Metaphysics 26
belong to man. Similarly, Socrates does not exhaust the intelligible content of humanity; by being
this man, with this flesh and these bones, Socrates is one limited instantiation of the universal man.
Now, because the distinction between man and animal and the distinction between
Socrates and man are logical or intentional distinctions, this participation of a species in its genus
or of a particular in a universal can be rightly characterized as a logical or intentional participation
rather than as an instance of real participation.31
To summarize, to receive in a particular way what belongs to something else in a universal
way is the general meaning of the term participation for St. Thomas, and it is exemplified by the
participation of a species in its genus and of a particular in the universal. St. Thomas then extends
the meaning of participation to a second set of cases, which involve composition:
Similiter etiam subiectum participat accidens et
materia formam, quia forma substantialis vel
accidentalis, que de sui ratione communis est,
determinatur ad hoc vel illud subiectum.
And similarly, a subject participates [its] accident
and matter [participates its] form, since a
substantial or accidental form, which is common
from its intelligible content, is determined to this
or that subject.
A subject—i.e., a substance—is said to participate (in) its accident, and matter participates
(in) form. These are both instances of composition that we will treat in greater detail later in the
course, in our consideration of the various ways in which ens commune is composite. As we will
see in these later treatments, St. Thomas will analyze both subject-accident composition and
matter-form composition as the composition of a principle of potency with an actualizing principle.
Again, what is fundamentally at issue in calling these cases participation is that the receiving
subjects—substance and matter—do not share in the character of the forms that they receive in an
exhaustive way. Because these examples of participation concern instances of real composition,
one can refer to this as real (or ontological) participation rather than logical participation—
although the claim that these are instances of real composition is something we will defend later in
the course.
Now, one might ask what the relationship is between the participation of an individual in a
universal and the participation of matter in form, since there seem to be examples that are closely
related: Socrates participates in man, and the matter of Socrates participates in the form or nature
of humanity. In the Commentary on the Metaphysics 1.10, immediately prior to the comments
about Pythagoras and Plato that we cited earlier, St. Thomas makes the following remarks:
Individuum autem est homo per participationem,
inquantum natura speciei in hac materia designata
participatur. Quod enim totaliter est aliquid, non
participat illud, sed est per essentiam idem illi.
Quod vero non totaliter est aliquid habens aliquid
aliud adiunctum, proprie participare dicitur. Sicut
But the individual is man by participation, insofar
as the nature of the species is participated in this
designated matter. For that which is something in a
total way, does not participate that [something], but
is that same thing by essence. But what is
something not totally, [rather] having something
31See Wippel 97 and his reference to Fabro and Geiger in n. 9 for this point.
Carl: Metaphysics 27
si calor esset calor per se existens, non diceretur
participare calorem, quia nihil esset in eo nisi
calor. Ignis vero quia est aliquid aliud quam calor,
dicitur participare calorem.
else joined [to it], is properly said to participate.
For example, if heat were a heat existing per se, it
would not be said to participate heat, since there
would be nothing in it but heat. But fire, since it is
something other than heat, is said to participate
heat.
The context for these remarks is that St. Thomas is presenting, so far as possible, the
Platonic account of participation in separate Forms in a positive light. We will return to this text in
its complete context later when we discuss the principle of individuation (the designated matter
that St. Thomas refers to in this text). For now, I only want to highlight that St. Thomas grounds
the participation of the individual in the universal in the participation of matter in form: the former
logical or intentional participation is grounded in a real participation and a real composition. For
this reason, here St. Thomas characterizes participation in the proper sense as the characteristic of
something that is joined to (i.e., composed with) something else.
We should also highlight as important the contrasting of what is per participationem with
what is per essentiam: one will find that St. Thomas frequently makes appeal to this distinction in
his writings.
Returning to our consideration of the Commentary on the De hebdomadibus, lec. 2, St.
Thomas then adds a third use of the term participation:
Et similiter etiam effectus dicitur participare suam
causam, et precipue quando non adequat virtutem
suae causae, puta si dicamus quod aer participat
lucem solis quia non recipit eam in claritate qua est
in sole.
And similarly too an effect is said to participate its
cause, and especially when [the effect] is not equal
to the power of its cause, as for example if we say
that air participates the light of the sun, since it
does not receive [light] with the brilliance it has in
the sun.
When something receives from its efficient cause a perfection that belongs to that cause,
but it receives that perfection in a limited or determinate way relative to the more complete
existence of that perfection in the cause, then that thing can be said to participate (in) the perfection
of the cause. St. Thomas does not offer any elaboration on this third case of participation, but it is a
usage that we will want to recall later.
To summarize, these are the cases or kinds of participation described by St. Thomas:
1) the participation of a species in a genus or of an individual in a species
2) the participation of substance in accident and of matter in form
3) the participation of an effect in its cause
5.3. Participation and Being
Conveniently enough, in the very text that we have considered as a source for St. Thomas’s
understanding of the notion of participation, St. Thomas is concerned with commenting on remarks
made by Boethius about participation and being. We can address ourselves to two questions in
Carl: Metaphysics 28
order: (1) does being participate in anything? (2) In what sense can beings (entia) be said to
participate in being (esse)? We will not at this time address either of these questions in full detail.
As mentioned before, some of the following comments will presume St. Thomas’s thesis that there
is real composition of essence and esse in created beings—this thesis will be considered as our
next major topic in this course.
To begin, it will be helpful to consider the text of Boethius about which St. Thomas is
commenting. The numbers here indicate the numbers of the seven axioms presented by Boethius:32
Does being participate in anything?
As we have seen before, one can understand being as that-which-is (id quod est, ens) or as
the existence or being (esse) that is the act of an essence. We find this very distinction articulated
in the first axiom of Boethius: esse and id quod est are diverse. St. Thomas comments on this
distinction as follows:
Dicit ergo primo quod diversum est esse et id quod
est, quae quidem diversitas non est hic referenda
ad res de quibus adhuc non loquitur, sed ad ipsas
rationes seu intentiones. Aliud autem significamus
per hoc quod dicimus esse et aliud per id quod
He says first therefore that esse and id quod est are
diverse, which diversity is not here referred to the
realities, of which he has not yet spoken, but to the
notions or intentions themselves. But we signify
one thing when we say esse and another when we
32The translation here is a translation of the text of Boethius as found in the Leonine edition of St. Thomas’s
Commentary. The translation is that of Janice Schultz and Edward Synan in their An Exposition of the
“On the Hebdomads” of Boethius (Washington, DC: The Catholic University of America Press, 2001),
xxxi & 15.
(1) Being (esse) and that-which-is (id quod est) are diverse. For being itself (ipsum esse) as yet is not.
That-which-is, however, once the form of being has been taken on, is and stands together.
(2) What-is (quod est) can participate in something, but being itself (ipsum esse) in no way participates
in anything. For participation occurs when something already is. Something is, however, when it has
received being (esse).
(3) That-which-is can possess something other than what it itself is. Being itself, however, has nothing
else outside itself as an admixture.
(4) However, to be something, and to be something in this, that [a thing] is, are diverse. For by the
former, accident is signified; by the latter, substance.
(5) Everything that is (omne quod est) participates in that which is being (eo quod est esse) with the
result that it be (ut sit). It participates in something else with the result that it be something. And
through this, that-which-is participates in that which is being with the result that it be. It is, however,
with the result that it can participate in anything else whatever.
(6) In every composite, being (esse) is other than the item itself. Every simple item possesses its being
(esse) and that-which-is (id quod est) as one.
(7) All diversity is discordant, whereas similitude must be sought. And what seeks something else is
shown to be itself by nature such as that which it seeks.
What we have set down as preliminaries, therefore, suffice. Each one will be applied in argumentation
by the prudent interpreter of their meaning.
Carl: Metaphysics 29
dicimus id quod est, sicut et aliud significamus
cum dicimus currere et aliud per hoc quod dicitur
currens. Nam currere et esse significatur in
abstracto sicut et albedo; sed quod est, id est ens et
currens, significatur in concreto velut album.
say id quod est, just as we also signify one thing
when we say “to run” and another when we say
“running.” For to run and to be (esse) are signified
in the abstract, like whiteness; but what is, that is, a
being (ens) and [one] running, are signified in the
concrete, like white [thing].
The distinction between esse and id quod est or ens is not initially to be construed as a real
distinction, but instead should be construed as a distinction in notion or intention—i.e., as a logical
distinction. Similarly, one can draw a logical distinction between “one running” and “to run,” or
between “white thing” and “whiteness,” as between the concrete and the abstract. Considered in
this way, therefore, the distinction between ens and esse is just the logical distinction between an
existent in the concrete and existence in the abstract.
Given this distinction between esse and id quod est, the question of whether being
participates in anything can therefore be understood in two ways: (a) Does esse participate in
anything? (b) Does that-which-is participate in anything?
Does esse participate in anything?
In his Commentary, following the preceding elaboration of the distinction between esse
and id quod est, St. Thomas immediately comments on the question of whether esse participates
anything:
Deinde cum dicit: Ipsum enim esse etc., manifestat
praedictam diversitatem tribus modis.
Quorum primus est quia ipsum esse non
significatur sicut subiectum essendi, sicut nec
currere significatur sicut subiectum cursus. Unde
sicut non possumus dicere quod ipsum currere
currat, ita non possumus dicere quod ipsum esse
sit; sed id quod est significatur sicut subiectum
essendi, velut id quod currit significatur sicut
subiectum currendi; et ideo sicut possumus dicere
de eo quod currit sive de currente quod currat in
quantum subicitur cursui et participat ipsum, ita
possumus dicere quod ens sive id quod est sit in
quantum participat actum essendi.
Then when he says: For being itself, etc., he shows
the aforementioned diversity in three ways.
Of these, the first is that being (esse) itself is not
signified as the subject of being, as “to run” is not
signified as the subject of running. Wherefore, just
as we cannot say that “to run” itself runs, so we
cannot say that being (esse) itself is; but that which
is (id quod est) is signified as the subject of being,
just as that which runs is signified as the subject of
running; and therefore just as we can say of that
which runs or of the runner that he runs insofar as
he is the subject of running and participates it, so
we can say that being (ens) or that which is (id
quod est) is insofar as it participates the act of
being (actus essendi).
Given only the logical distinction between ens and esse as the distinction between the
concrete and the abstract, it cannot be said that esse participates ens; rather, ens participates esse
insofar as it is the subject of esse, just as the runner is the subject of and participates running, rather
Carl: Metaphysics 30
than vice versa. St. Thomas proceeds to explain that it is for this reason that Boethius next says
being itself as yet is not (ipsum esse nondum est): ens is, because ens is the subject of esse, but esse
is not the subject of anything, and so it cannot be said that esse is any more than it is said that to
run runs.
After providing the threefold explanation of the notion of participation that we considered
above, St. Thomas proceeds to offer more comments concerning the (im)possibility that esse
should participate in anything:
Praetermisso autem hoc tertio modo participandi,
impossibile est quod secundum duos primos
modos ipsum esse participet aliquid. Non enim
potest participare aliquid per modum quo materia
vel subiectum participat formam vel accidens quia
ut dictum est ipsum esse significatur ut quiddam
abstractum. Similiter autem nec potest aliquid
participare per modum quo particulare participat
universale; sic enim etiam ea quae in abstracto
dicuntur participare aliquid possunt sicut albedo
colorem, sed ipsum esse est communissimum,
unde ipsum quidem participatur in aliis, non autem
participat aliquid aliud.
But this third mode of participating set aside, it is
impossible that being (esse) itself participate
something according to the first two modes. For it
cannot participate something through the mode by
which matter or a subject participates form or
accident, since as was said being (esse) itself is
signified as something abstract. Nor similarly can
it participate something through the mode by
which a particular participates a universal; for in
this way too those things which are said in the
abstract can participate something, as whiteness
participates color, but being (esse) itself is most
common, indeed such that it is participated by
others, but it does not participate something else.
Without commenting at this moment on the third mode of participation, St. Thomas
excludes the first two modes of participation with regard to esse itself as that which participates.
However, in his explanation, he has noted that esse is most common (communissimum), with the
consequence that other things participate in esse, but esse does not participate in anything else.33
Does that-which-is participate in anything?
Thus, it will come as no surprise that St. Thomas defends the view that that-which-is does
participate in something else. First, and most importantly, it can be said that ens participates in
esse. Our purpose for now is to sketch only a general sense in which such a claim may be
articulated: fuller clarity about participation in esse will come only after we have discussed the real
composition of essence and esse in created substances and the existence of God, to Whom St.
Thomas will refer as ipsum esse per se subsistens.34 St. Thomas continues, in the text we have been
studying as follows:
33As we will discover later, this is a way of saying that esse is a transcendental term. St. Thomas often refers
to the transcendentals as the communissima.
34It must suffice for now to note that the qualification per se subsistens serves to distinguish the divine esse
from ipsum esse in the sense of esse commune (the act of [created] being in general). Esse commune is
signified in the abstract, as something that is not per se subsistens.
Carl: Metaphysics 31
Sed id quod est sive ens, quamvis sit
communissimum, tamen concretive dicitur, et ideo
participat ipsum esse, non per modum quo magis
commune participatur a minus communi, sed
participat ipsum esse per modum quo concretum
participat abstractum. Hoc est ergo quod dicit quod
id quod est, scilicet ens, participare aliquo potest;
sed ipsum esse nullo modo participat aliquo; et
hoc probat ex eo quod supra dictum est, quod
scilicet ipsum esse nondum est. Manifestum est
enim quod id quod non est non potest aliquo
participare, unde consequens est quod participatio
conveniat alicui cum iam est; sed ex hoc aliquid
est quod suscipit ipsum esse sicut dictum est. Unde
relinquitur quod id quod est aliquid possit
participare, ipsum autem esse non possit aliquid
participare.
But that-which-is or being (ens), although it is
most common, nevertheless is said concretely, and
therefore it participates being (esse) itself, not
through the mode by which the more common is
participated by the less common, but [that-whichis] participates being (esse) itself through the mode
by which the concrete participates the abstract.
This, therefore, is what he says, that that-which-is,
namely being (ens), can participate in something;
but being (esse) itself in no way participates in
anything; and he proves this from what was said
above, namely that being (esse) itself as yet is not.
For it is manifest that that-which-is-not cannot
participate in anything, whence it follows that
participation belongs to something when it already
is; but something is by this that it receives being
(esse) itself, as was said. Wherefore, it remains that
that-which-is can participate something, but being
(esse) itself cannot participate anything.
It is important to emphasize that the participation of ens in esse as articulated here
presumes only the logical distinction between the concrete and the abstract: ens participates esse
just as a runner participates in “to run,” and a white thing participates in whiteness. As St. Thomas
is careful to point out, the participation of ens in esse is not even a case of participation of the less
common in the more common, because both ens and esse are communissimum, most common.
Nevertheless, as we shall see in consideration of our next major topic (real composition of essence
and esse in created substances), St. Thomas is here paving the way for an argumentation for a real
distinction rather than a merely logical distinction between that-which-is and esse itself.
We will comment more in a moment on the claim that that-which-is (ens) can be said to
participate being (esse). For now, we should note another sense in which ens is said to participate
in something. We have already observed that a substance can be said to participate an accident.
According to the analogical character of ens, which is predicated primarily of substance, the
participation of substance in accident is the participate of ens in something. St. Thomas speaks
about substance-accident participation as the participation of ens in something later in the same
text we have been considering at length, Exp. De heb. lec. 2.
First, it should be noted that just as St. Thomas characterizes the participation of ens in
esse at first according to the participation of the concrete in the abstract, so too does he note that
human participates humanity and that white participates whiteness.
Ex hoc autem quod homo habet humanitatem vel
album albedinem, non prohibetur habere aliquid
But from this that man has humanity or white
whiteness, it is not precluded [that it] have
Carl: Metaphysics 32
aliud quod non pertinet ad rationem horum, nisi
solum quod est oppositum hiis; et ideo homo et
album possunt aliquid aliud habere quam
humanitatem vel albedinem; et haec est ratio quare
albedo et humanitas significantur per modum
partis et non praedicantur de concretis sicut nec
aliqua pars de suo toto. Quia igitur, sicut dictum
est, ipsum esse significatur ut abstractum, id quod
est ut concretum, consequens est verum esse quod
hic dicitur quod id quod est potest aliquid habere
praeter quam quod ipsum est, id est praeter suam
essentiam, sed ipsum esse nihil aliud habet
admixtum praeter suam essentiam.
something other that does not pertain to the
intelligible content of these, except only that which
is opposed to these; and therefore man and white
can have something other besides humanity or
whiteness; and this is the reason why whiteness
and humanity are signified in the manner of a part
and are not predicated of concrete [items], just as a
part [is] not [predicated] of its whole. Since
therefore, as was said, being (esse) itself is
signified as abstract, [and] that-which-is as
concrete, it follows that what is said here is true,
that that-which-is can have something other than
what it itself is, that is, outside its essence, but
being (esse) itself has nothing else admixed outside
its essence.
This possibility of ens receiving something not contained in its own essence is articulated
in two ways by St. Thomas: (1) in terms of the reception of esse, which is not contained in the
content of a thing’s essence; and (2) in terms of the reception of an accident, which is also not
contained in the content of a thing’s essence. To discuss the first kind of reception by ens of
something not contained in its essence will be the next major topic of discussion—the real
composition of essence and esse—to which we will turn shortly. For now, we want to consider the
participation of ens in accident, which St. Thomas considers in the same text:
Si vero sit talis forma quae sit extranea ab essentia
habentis eam, secundum illam formam non dicitur
habens esse simpliciter, sed esse aliquid, sicut
secundum albedinem homo dicitur esse albus. . . .
Dicit quod ad hoc aliquid sit simpliciter subiectum
participat ipsum esse, sed ad hoc quod sit aliquid,
oportet quod participet aliquo alio, sicut homo ad
hoc quod sit albus participat non solum esse
substantiale sed etiam albedinem.
But if the form be such that it is extraneous to the
essence of what possesses it, according to that
form it is not called something having being
(habens esse) without qualification, but [something
having] to-be-something (esse aliquid), as
according to whiteness man is said to be white. . . .
He says that for this that something be a subject
without qualification it participates being (esse)
itself, but for those that it be something, it is
necessary that it participate something else, as
man, for this that he be white, participates not only
substantial being (esse) but also whiteness.
The participation of a substance in accident is thus a kind of participation of ens or id quod
est in something else, because it does not pertain to this or that subject to include in its essence this
Carl: Metaphysics 33
or that accidental characteristic. In this way, then, ens can be said to participate in something.
To summarize, then, ens or that-which-is can be said to participate in two general ways: it
participates in esse, and it participates in accident. With regard to the former, so far we have
articulated only a logical or intentional way in which ens participates esse: we will now turn to the
distinct senses in which the participation of ens in esse can be understood.
In what distinct senses can beings (entia) be said to participate being (esse)?
We have already indicated that ens participates esse as the concrete participates the
abstract, just as white participates whiteness. So, it will be no surprise at this point that St. Thomas
does affirm that beings (entia) participate being (esse). However, by such an expression St.
Thomas typically means more than just the expression of a logical or intentional distinction
between the concrete being and its act of being taken in the abstract (which can be compared to the
concrete runner and his act of running taken in the abstract). We will here comment briefly on a
subject to which Msgr. Wippel devotes considerable attention (pp. 110-24): what does it mean to
say that beings participate esse? Following Msgr. Wippel’s presentation, we can distinguish three
senses in which this claim can be taken. Because the following comments will presuppose both the
real composition of essence and esse in finite realities and the existence of God, Who is ipsum esse
per se subsistens, what we are considering can be said to be usages of the phrase “participation in
esse” that will only be justified by virtue of arguments that will be given later in the course.35
(1) To participate in esse can be understood as to participate in esse commune, which is
esse understood as an analogically common perfection in which all finite or composite realities
share. This esse commune is not to be identified with God; rather, as will be discussed later in the
course, esse commune is caused by God. When we say that esse commune is an analogically
common perfection, we mean to exclude that esse commune be understood as a separate form
distinct from the individuals that participate it. That is, esse commune is not a Platonic Form.
Rather, each concrete ens possesses its own esse or act of existence, and insofar as one considers
esse to be a perfection shared in common, one calls this esse commune.
(2) To participate in esse can be understood as to participate in ipsum esse per se
subsistens, that is, in divine esse. This is not St. Thomas’s preferred mode of expression, but he
does speak in this way on occasion. This can only be understood as the participation of an effect in
its cause: one must exclude any notion that the divine esse itself is somehow communicated or
diversified in created beings. As Msgr. Wippel details, for this reason more often says that finite
beings participate a likeness of the divine esse, by which he means that they participate their own
esse, which is caused by and bears some likeness to the divine esse. Alternatively, St. Thomas will
say that beings participate esse from God. As Msgr. Wippel notes, the participation of beings in
esse commune is therefore ultimately grounded in their participation in divine esse, understood as
the participation of an effect in its cause.
(3) A being can be said to participate in esse insofar as it participates its own act of
existence: this is like the participation in esse commune, but one considers this concrete being’s act
of existence in particular rather than considering esse as a perfection that is analogically common
to many. What does it mean to say that this being participates its own actus essendi? The answer to
this question can only be given by answering a much more difficult question, to which we will
given only limited attention in this course: What is it that accounts for the limited or finite
character of a created reality? The claim that a finite being participates its own actus essendi can be
well understood, if one accepts the claim that it is primarily a thing’s essence rather than its esse
35See Msgr. Wippel’s summary remarks on pp. 120-21.
Carl: Metaphysics 34
that should be taken as the principle according to which it is finite and limited.36
36For Msgr. Wippel’s preliminary remarks on this point of dispute, see pp. 124-31.
Carl: Metaphysics 35
6. Real Composition of Essence and Esse in Finite Beings
Having noted that being in general (ens commune) is a common subject of study according
to analogical rather than univocal unity, we can proceed to a consideration of ens taken in its
primary referent, which is substance. What the predicamental analogy of being allows us to do, in
our consideration of ens commune (the subject of metaphysics), is to justify this initial focus on
substance. Because of the analogy of being, we understand that whatever we say about substance
will have implications for what we will say about accidents.
The central note of St. Thomas’s analysis of finite being, and particularly of substance, is
that finite being is composite, in various ways. We will begin with what is perhaps St. Thomas’s
most famous metaphysical thesis, the real distinction and composition of esse and essence in finite
beings.
6.1. Background: Relation of Concepts to Reality; Real and Logical Distinction
Medieval philosophers and theologians generally recognized a distinction between esse
(existence) and essence in created things, but it was a matter of significant dispute whether this
distinction is a real distinction or merely a logical or conceptual distinction. That is, is this
distinction between esse and essence a real feature of the world even apart from the consideration
of the mind? Or is it a distinction that only exists in the mind, in the way that (for example) the
distinction between dog and animal is a logical distinction that is not really present in a dog?37
To understand the question posed, we should draw two related distinctions. First, St.
Thomas distinguishes between three ways in which a concept of the intellect can be related to
things outside the mind, as follows:38
(1) What is conceived by the intellect can be a similitude (i.e., a likeness) of something
existing outside the mind. For example, one’s concept of man is a likeness of a thing existing
outside the mind, that is, of a man. Such a concept has an immediate foundation in the thing
outside the mind, insofar as the concept of man is a likeness of the essence of man; and this
likeness comes to exist as the product of the act of understanding.39
(2) What is conceived by the intellect is sometimes not a likeness of anything outside the
mind, but is rather something that arises from the activity of understanding. For example, the
concept of a genus is not a similitude of anything existing outside the mind; rather, it is a concept
that arises is consideration of the relationship between the essence animal and the various kinds of
things that possess this essence. The concept of genus has its foundation in things outside the mind;
this is not an immediate foundation, but a remote foundation. (These intentions, such as genus or
species, are typically called second intentions, as distinguished from first intentions, which are
concepts of the first kind distinguished above.)
(3) Finally, what is conceived by the intellect can fail to be a likeness of anything outside
37That is, in reality, a dog is not “composed” of animal and dog. This can be recognized from the fact that the
ratio of dog includes the ratio of animal.
38In Sent. 1.2.1.3.
39It should be noted that the concept taken in this sense is distinct from the intelligible species that is
abstracted from the phantasm. The intelligible species is the formal principle of the act of understanding,
whereas the concept is the terminus or product of the act of understanding. Both the intelligible species
and the concept are likenesses of the thing outside the mind, but one does not possess any awareness of
an intelligible species, while one is aware of one’s concept.
Carl: Metaphysics 36
the mind, such as the concept of a chimera. Such a concept has no foundation except the mind
itself.
Now, one can also draw a related distinction between two kinds of distinction: this is the
distinction between a real distinction and a distinction of reason.
(a) In a real distinction, one distinguishes two items that are distinct in reality even apart
from the consideration of the mind, because the two items are not identical in reality. For example,
a man is really distinct from a dog, even prior to the consideration of the mind. This is obviously a
case of a real distinction, because a dog and a man possess independent existence as substances.
(b) In a distinction of reason (or a logical or conceptual distinction), one draws a
distinction between things that are not absolutely distinct apart from the consideration of the mind.
That is, one considers a single thing according to distinct concepts. An obvious example of a
distinction of reason is the distinction between the morning star and the evening star (which are
identical in reality: they are both the planet Venus). St. Thomas will also say (as we will see later in
our course) that the divine attributes are not really distinct but are only distinct according to reason.
Indeed, the texts where St. Thomas brings up the difference between real and logical distinction are
almost exclusively concerned with theological questions: he affirms on the one hand that the
distinction between the divine Persons is a real distinction40, whereas the distinction between the
divine attributes is a distinction of reason.41
A number of later authors (such as Ockham) will understand real distinction exclusively as
the distinction between one thing (res) and another thing (res) which exist or can exist
independently from one another, such as a man and a dog or a man and his arm. If this is what is
meant by a real distinction, then a real distinction always implies the possible separate existence of
the items distinguished. This is not, however, how St. Thomas understands a real distinction: it is
not a requirement for a real distinction that the items distinguished be capable of existing
independently from one another.
For example, as we will explain below, for St. Thomas the distinction between substantial
form and prime matter is a real distinction, because these are two principles that enter into real
composition in a corporeal substance: but neither the matter nor the form is capable of existing
independently of the composite. (The only exception to this is the human soul, which is a
substantial form that survives the corruption of the human substance.) Substantial form and matter
are really distinct, according to St. Thomas’s understanding of real distinction, despite the fact that
neither the substantial form (except for the human soul) nor the prime matter is capable of
independent existence as a thing.
Much of the controversy about whether the distinction between essence and esse is a real
distinction or only a distinction of reason hinges on what one understands as the implications of a
real distinction with regard to the possible independent existence of the items distinguished.
Therefore, when we argue that essence and esse are really composite and really distinct in created
things, we do not mean to imply (absurdly) that an essence could exist apart from its esse.
6.2. Argument for Real Composition of Essence and Esse
One can distinguish in St. Thomas’s writings a variety of ways of arguing for the claim that
40See In Sent. 1.2.1.5.
41See In Sent. 1.2.1.3.
Carl: Metaphysics 37
esse and essence are really distinct and composite in finite beings. With our limited time, we will
begin by considering St. Thomas’s comments concerning real composition in the context of the
long text to which we have given significant attention under the heading of participation, Exp. De
heb., lec. 2. In this place, St. Thomas writes:
Deinde cum dicit: Omni composito etc., ponit
conceptiones de composito et simplici, quae
pertinent ad rationem unius, et est considerandum
quod ea quae supra dicta sunt de diversitate ipsius
esse et eius quod est, est secundum ipsas
intentiones. Hic ostendit quomodo applicetur ad
res; et primo ostendit hoc in compositis, secundo
in simplicibus, ibi: Omne simplex etc.
Est ergo primo considerandum quod sicut esse et
quod est differunt secundum intentiones, ita in
compositis differunt realiter. Quod quidem
manifestum est ex praemissis. Dictum est enim
supra quod ipsum esse neque participat aliquid ut
eius ratio constituatur ex multis, neque habet
aliquid extrinsecum admixtum ut sit in eo
compositio accidentalis; et ideo ipsum esse non est
compositum; res ergo composita non est suum
esse; et ideo dicit quod in omni composito aliud est
esse ens et aliud ipsum compositum quod est
participando ipsum esse.
Then when he says: In every composite etc., he
posits conceptions about the composite and the
simple, which pertain to the character of unity, and
it must be considered that those things said above
about the diversity of being (esse) itself and of
what-is (quod est), is according to the intentions
themselves. Here he shows how [this] is applied to
things; and first he shows this about composites,
second about simples, where [he says]: Every
simple etc.
Therefore first it must be considered that just as
being (esse) and what is (quod est) differ according
to intention, so also in composite [things] they
differ really. Indeed this is manifest from what
preceded. For it was said above that being (esse)
itself neither participates anything as though its
ratio were constituted from many, nor does it have
something extrinsic admixed with it as though
there were in it accidental composition; and
therefore being (esse) itself is not composite;
therefore a composite thing is not its esse; and
therefore he says that in every composite it is one
thing to be a being (esse ens) and another to be the
composite itself, which is, by participating ipsum
esse.
The most famous text concerning the distinction of essence and esse, that found in c. 4 of
the De ente et essentia.42 We can distinguish two stages in the argument presented in this text. The
first stage presents a version of what is often called St. Thomas’s intellectus essentiae
(understanding of an essence) argument. The context of this passage is that St. Thomas is
commenting on the characteristics of simple, intelligible essences (i.e., angels).43
42See Wippel 137-150 for
43All quotations are from the Goodwin translation.
Carl: Metaphysics 38
Stage 1: intellectus essentiae argument
Even though intelligences are simple (or non-composite) insofar as they are not composed
of matter and form, nevertheless St. Thomas wants to argue that there is some potency in them,
such that they are not pure act. (As we will explain later, St. Thomas holds that God alone is
absolutely pure act without any admixture of potency). St. Thomas now begins to offer his
argument for the claim that intelligences are composite in some way:
St. Thomas’s argument begins with the assertion that a given essence includes as
intelligible parts all of those things without which that essence cannot be understood. For example,
rational, animal, flesh, and bones are all intelligible parts of the essence of man: one does not
understand what a man is without knowing these parts of the essence. Anything that belongs to a
particular man besides these essential notes does so because of some kind of composition with
something extraneous to the essence of man. For example, that a man is white or tall or educated is
a matter of composition with these accidental forms.
Now St. Thomas notes that the esse of a thing is not one of these intelligible parts of an
essence, because one can