Aquinas uses the expression actus essendi in the Summa theologiae
only once, in part I, question 3, article 4, ad 2.
In this article of the Summa, Aquinas explains that in
God, essentia and esse are not two distinct metaphysical principles
as is the case in creatures; in the Creator essentia and esse are
one and the same reality. The expression actus essendi appears in the answer
to the second of the only two objections addressed in the article. The body of the article is devoted to explaining why God
is His own esse. And the answer to the first objection offers a brief explanation
of the difference between the esse of God and esse commune. Here is
a quick look at this context.
Aquinas had shown in the preceding article (article 3) that God
is His own essence. He based his argumentation on the fact that in material things,
the natura and the suppositum are distinct: In material things the
suppositum includes not only the nature of the thing but also other elements
that fall outside the scope of the nature such as accidents and individual matter.
Even in Angels there are accidental perfections that fall outside the scope of the
angel’s essence and so, to a certain extent, angels also possess a suppositum
that cannot be said to be exactly the same as their natura. (For more on
the distinction between suppositum and natura in the case of angels,
see John F. Wippel, The Metaphysical Thought of Thomas Aquinas [Washington, D.C.:
Catholic University of America Press, 2000], 238-253.)
In God, however, nothing can fall outside the scope of His own
nature. God’s nature is itself per se a subsisting individual distinct from
all other reality. God’s nature is such that it precludes any addition; therefore,
in God nature and suppositum are the same. God is His own essence. Having
established this, Aquinas now proceeds to show that God also is His own esse.
Three reasons are offered in the present article (article 4) as follows:
(1) Anything inhering in a subsisting thing that does not belong
per se to the essence of the thing is either caused by the constituent principles
of the essence or caused by some exterior agent. (This is illustrated with two examples:
(a) A property such as the human being’s ability for laughing—which if lacking would
constitute a privation—is caused by the constituent principles of the essence of
a human being; and (b) the quality of heat in hot water is caused by fire which
is exterior to water.)
Now, regarding the inherent esse of things, Aquinas reasons
as follows. If in a thing esse is distinct from essence, then this esse of the thing must be caused either by some exterior agent or by the thing’s essential principles.
It is impossible for a thing’s esse to be caused by its own essential constituent principles, for nothing can be the sufficient cause of its
own esse, if its esse is caused. The guiding principle here is the
impossibility of having an efficient cause that is capable of producing itself prior
to its own existence.
(See Summa theologiae, part I, question 2, article
3, corpus: "Nec tamen invenitur nec est possibile quod aliquid sit causa
efficiens sui ipsius; quia sic esset prius seipso, quod est impossibile;" and
De ente et essentia, chapter 3: "Non autem potest esse quod ipsum esse
sit causatum ab ipsa forma vel quiditate rei—dico sicut a causa efficiente—quia
sic aliqua res esset sui ipsius causa et aliqua res seipsam in esse produceret,
quod est impossibile.")
Therefore that thing whose esse differs from its essence
must have its esse caused by another.
But this cannot be true of God because God is the uncaused cause.
Therefore it is impossible that God’s esse should differ from His essence.
God is His own esse.
(Summa theologiae, part I, question 3, article 4, corpus: Primo quidem, quia quidquid est
in aliquo quod est praeter essentiam eius, oportet esse causatum vel a
principiis essentiae, sicut accidentia propria consequentia speciem, ut
risibile consequitur hominem et causatur ex principiis essentialibus speciei;
vel ab aliquo exteriori, sicut calor in aqua causatur ab igne. Si igitur ipsum
esse rei sit aliud ab eius essentia, necesse est quod esse illius rei vel sit
causatum ab aliquo exteriori, vel a principiis essentialibus eiusdem rei.
Impossibile est autem quod esse sit causatum tantum ex principiis essentialibus
rei, quia nulla res sufficit quod sit sibi causa essendi, si habeat esse
causatum. Oportet ergo quod illud cuius esse est aliud ab essentia sua, habeat
esse causatum ab alio. Hoc autem non potest dici de Deo, quia Deum dicimus esse
primam causam efficientem. Impossibile est ergo quod in Deo sit aliud esse, et
aliud eius essentia.)
(2) The second reason comes from the observation that esse
is the actuality of every form or nature. Goodness and humanity, for example, are
said to be real on account of the esse of the subsisting thing that instantiates
goodness and humanity. Therefore, in things whose essence is distinct from esse,
esse must compare to essence as act to potency. But in article 1, Aquinas
had already shown that in God there is no potency. It follows then that in God essence
does not differ from esse. God’s essence and God’s esse are identical.
(Summa theologiae, part I, question 3, article 4, corpus: Secundo, quia esse est
actualitas omnis formae vel naturae, non enim bonitas vel humanitas
significatur in actu, nisi prout significamus eam esse. Oportet igitur quod
ipsum esse comparetur ad essentiam quae est aliud ab ipso, sicut actus ad
potentiam. Cum igitur in Deo nihil sit potentiale, ut ostensum est supra,
sequitur quod non sit aliud in eo essentia quam suum esse. Sua igitur essentia
est suum esse.)
And (3) just as something on fire that is not the fire itself
is said to be on fire by participation, so also that which has esse but is
not esse itself is said to be an ens by participation. But since it
was shown above that God is His own essence, if God were not also His own esse,
it would follow that He would then be ens per participationem, and
not the ens per essentiam. And this would in turn show that God is not the
first ens which is absurd. Therefore God is His own esse, and not
merely His own essence.
(Summa theologiae, part I, question 3, article 4, corpus: Tertio, quia sicut illud quod
habet ignem et non est ignis, est ignitum per participationem, ita illud quod
habet esse et non est esse, est ens per participationem. Deus autem est sua
essentia, ut ostensum est. Si igitur non sit suum esse, erit ens per
participationem, et non per essentiam. Non ergo erit primum ens, quod absurdum
est dicere. Est igitur Deus suum esse, et non solum sua essentia.)
With this background Aquinas proceeds to answer the two objections.
In the first objection it is argued that God’s essence is not
identical to God’s esse because if this were the case then nothing should
be added to God’s esse. But the esse to which no addition is made
is esse commune which is predicated of all things. God would therefore be
esse commune. But this is false, for revelation tells us that men have wrongly
attributed the name of God to stones and wood thinking that there was something
divine in them. (See Wis.
14:21.) Therefore God’s esse is not God’s essence.
(Summa theologiae, part I, question 3, article 4, obj.
1: Videtur quod in Deo non sit idem essentia et esse. Si enim hoc sit, tunc ad esse
divinum nihil additur. Sed esse cui nulla fit additio, est esse commune quod de
omnibus praedicatur, sequitur ergo quod Deus sit ens commune praedicabile de omnibus.
Hoc autem est falsum, secundum illud Sap. XIV: Incommunicabile nomen lignis et lapidibus
imposuerunt. Ergo esse Dei non est eius essentia.)
In answer to this objection Aquinas explains that esse sine
additione can be understood in two ways. In one way, he says, esse sine additione
is that esse that precludes addition, and he illustrates this with the example
of irrational animals whose essence precludes the addition of reason.
But in another
way, Aquinas continues, esse sine additione can be understood to be that
esse which does not preclude addition. The addition of reason for example,
he says, is not precluded in the scale of animal beings as such.
God’s esse
can be said to be esse sine additione in the first sense because God’s esse
precludes addition; esse commune, on the other hand, is esse sine additione
in the second sense, that is to say, esse commune is that esse that
does not preclude addition.
(Summa theologiae, part I, question 3, article 4, ad 1:
Ad primum ergo dicendum quod aliquid cui non fit additio potest intelligi dupliciter.
Uno modo ut de ratione eius sit quod non fiat ei additio, sicut de ratione animalis
irrationalis est, ut sit sine ratione. Alio modo intelligitur aliquid cui non fit
additio quia non est de ratione eius quod sibi fiat additio, sicut animal commune
est sine ratione, quia non est de ratione animalis communis ut habeat rationem,
sed nec de ratione eius est ut careat ratione. Primo igitur modo, esse sine additione,
est esse divinum; secundo modo, esse sine additione, est esse commune.)
In the Summa contra gentiles, book I, chapter 26, Aquinas
offers a more complete explanation of why God cannot be said to be esse commune.
That which is common, he affirms, is specified or individuated through addition.
Through addition to esse commune one can reach down to the esse proprium.
What is common or universal cannot exist without addition, but can intellectually
be considered without addition.
The concept of animal, he now explains, is not instantiated
in reality without the difference rational or the difference irrational, although
the concept animal can be understood without these differences.
What is more, although
a universal concept may be considered without addition, it cannot be understood
without the receptibility of addition; for, if no difference could be added to the
concept animal, it would not be a genus.
But God’s esse is without addition
not only in the consideration of reason but also in reality; and not only is the
esse of God, esse without addition, the esse of God is also
esse without the receptibility of addition.
Thus, since God’s esse
neither receives nor can receive addition one can rather conclude that God is not
esse commune but esse proprium, for God’s esse is distinguished
from all the rest by the fact that nothing can be added to it.
(Summa contra gentiles, book I, chapter 26: Quia enim id quod commune est
per additionem specificatur vel individuatur, [aliqui] aestimaverunt divinum esse, cui nulla
fit additio, non esse aliquod esse proprium, sed esse commune omnium; non considerantes
quod id quod commune est vel universale sine additione esse non potest, sed sine
additione consideratur: non enim animal potest esse absque rationali differentia,
quamvis absque his differentiis cogitetur. Licet etiam cogitetur universale absque
additione, non tamen absque receptibilitate additionis: nam si animali nulla differentia
addi posset, genus non esset; et similiter est de omnibus aliis nominibus. Divinum
autem esse est absque additione non solum in cogitatione, sed etiam in rerum natura:
nec solum absque additione, sed etiam absque receptibilitate additionis. Unde ex
hoc ipso quod additionem, non recipit nec recipere potest, magis concludi potest
quod Deus non sit esse commune, sed proprium: etiam ex hoc ipso suum esse ab omnibus
aliis distinguitur quod nihil ei addi potest. Unde Commentator in libro De Causis
dicit quod causa prima ex ipsa puritate suae bonitatis ab aliis distinguitur et
quodammodo individuatur.)
Finally Aquinas addresses a second objection against the identity
of God’s essence and God’s esse. The objection is an argument based on the
fact that about God one can only answer the question an sit and not the question
quid sit. It is in answer to this objection that Aquinas uses the expression
actus essendi.
In his answer Aquinas explains that the verb esse has
two meanings. In its primary signification, esse means the actus essendi,
and in its extended meaning esse connotes the composition of a proposition
effected by the mind in joining a predicate to a subject.
While granting that about God one cannot answer the question quid
sit, Aquinas appeals to the primary meaning of esse to hold also that
it is not by knowing God’s actus essendi that one can answer the an sit
question about God.
One can indeed answer the an sit question about God,
but by appealing to the extended meaning of esse.
Aquinas explains that one can establish the truth of the proposition
“God is” through a sequence of judgments whose connection is established through
reasoning from God’s effects. But the esse thus known by the human intellect
is not God’s actus essendi. Hence, the argument of the second objection does
not follow.
Regarding this use of the expression actus essendi, here
is Aquinas in his own words:
Objection 2:
Praeterea, de Deo scire possumus an sit, ut supra (qu.
2, art. 2) dictum est. Non autem possumus scire quid sit. Ergo non est idem
esse Dei, et quod quid est eius, sive quidditas vel natura (Summa theologiae,
part I, question 3, article 4, obj. 2, Rome: Leonine edition, 1888, vol. 4, p. 42,
column A).
Answer to objection 2:
Ad secundum dicendum quod esse dupliciter dicitur: uno modo,
significat actum essendi; alio modo, significat compositionem propositionis, quam
anima adinvenit coniungens praedicatum subiecto. Primo igitur modo accipiendo esse,
non possumus scire esse Dei, sicut nec eius essentiam: sed solum secundo modo. Scimus
enim quod haec propositio quam formamus de Deo, cum dicimus Deus est, vera
est. Et hoc scimus ex eius effectibus, ut supra (qu. 2, art. 2) dictum est (Summa theologiae, part I, question 3, article 4, ad 2, Rome: Leonine edition, 1888, vol. 4, p. 42, column B).
In this text it is clear that Aquinas does not connect God’s actus
essendi with the knowledge of the esse of God that the human intellect
is capable of reaching through God’s effects. The esse of God known though
God’s effects is the esse that answers the question an Deus sit, that
is to say, the question of God’s existence. But esse in its meaning of God’s actus
essendi answers rather the question of God’s essence, the quid est of
God.
Therefore, in the present context something that may seem obvious
needs to be emphasized. The issue of how to reason and conclude correctly about
God’s actus essendi is not to be confused with the issue of how to reason
and conclude correctly about God’s existence.
Two different paths can be easily
traced about the historical development of these two issues. In his understanding
of esse, Aquinas distinguishes clearly between the esse that answers
the question of existence (an sit) and the esse that connotes the
metaphysical principle of actus essendi.
Commenting on the meanings of esse, J. F. Wippel remarks
that “Aquinas is only too aware that the term esse (literally: ‘to be’) can
be used with different meanings. For instance, in an early texts from his Commentary
in I Sentences (d. 33, q. 1, a. 1, ad 1), he distinguishes three different
meanings for it. As he puts it there, the term esse may be taken to signify
the very quiddity or nature of a thing, as when we refer to a definition as signifying
what a thing’s esse is; for, as Thomas remarks, a definition signifies the
quiddity of a thing” (Wippel, The Metaphysical Thought of Thomas Aquinas,
24-25).
In the footnote to this sentence Wippel writes: “Here Thomas is
discussing the nature of relations in the Trinity. In responding to an objection
he comments: ‘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’ (Mandonnet ed., Vol. 1,
pp. 756-66).”
“Secondly,” Wippel continues, “esse may signify the very
act of an essence, meaning thereby not its second act or operation but its first
act, i.e., its actual existence.”
“Taken in a third way,” proceeds Wippel, “esse signifies
the truth of composition, that is, of judgment, as this is expressed in propositions.
In this sense, continues Thomas, the verb ‘is’ is referred to as copula. When used
in this way esse is realized in the full sense in the intellect which composes
or divides. Nonetheless, when so used this esse itself is grounded in the
esse of the thing, that is, in the act of its essence (its existence) just
as truth is.”
The footnote for this line reads as follows: “‘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’ (p. 766). Concerning truth cf. In I Sent., d. 19,
q. 5, a. 1 (cited below in n. 16).”
“Of these three usages,” Wippel remarks, “the first may strike
the reader as somewhat surprising. In many other context Thomas is content simply
to distinguish between esse insofar as it signifies the composition of a
proposition which the intellect effects through judgment, and esse that is
actual existence or, as Thomas often expresses it, as the actus essendi (act
of being). In other words, he often limits himself to the second and third meanings
he has singled out in the present text. For instance, he appeals to this twofold
distinction in Summa Theologiae I, q. 3, a. 4 in order to meet an objection
against his claim that in God essence and esse (act of being) are identical.”
As footnote to this passage, one reads: “Leon. 4.42. Note:
‘Ad secundum dicendum quod esse dupliciter dicitur: uno modo, significat actum essendi;
alio modo, significat compositionem propositionis, quam anima adinvenit coniungens
praedicatum subiecto.’ Also see Quodlibet XII, q. 1, a. 1, ad 1: ‘…esse dupliciter
dicitur: quandoque enim esse idem est quod actus entis; quandoque autem significat
compositionem enuntiationis et sic significat actum intellectus’ (Leon. 25.2.399:34-38).
Cf., however, Thomas remark on De potentia, q. 7, a. 2, ad 1: ‘Ad primum
ergo dicendum, quod ens et esse dicitur dupliciter, ut patet V Metaph. Quandoque
enim significat essentiam rei, sive actum essendi; quandoque vero significat veritatem
propositionis …’ See Quaestiones disputatae, vol. 2, M. Pession ed. (Turin-Rome,
1953), p. 191. Also see In V Met., lect. 9, pp. 238-40, nn. 889-896” (Wippel,
The Metaphysical Thought of Thomas Aquinas, 24-25).
Jan A. Aertsen for his part commented briefly on the text from
Summa Theologiae, part I, question 3, article 4, ad 2, in his discussion
on the relationship between the “if” question (the question an sit) and the
“what is” question. Here is a lengthy quotation from Aertsen’s reflections on this
subject found in his Nature and Creature: Thomas Aquinas’s Way of Thought,
(Leiden, The Netherlands: E. J. Brill, 1988), 20-23.
On the issue of whether or not the question an est is the
most fundamental question Aertsen comments first that “In the second book of the
Posteriora Analytica (89 b 38-90 a 1: 90 a 8 ff.) Aristotle says only this:
‘Whenever we know if something is, we ask what it is.’ The ‘if’ question is twice
dismissed in this manner in passing. Thomas speaks more extensively of it in various
loci in his writings and places the answer to the question an est within
a dichotomy of being, namely, extra-mental and intra-mental being.”
In the footnote to these remarks Aertsen writes: “See S.Th.
I, 3, 4, ad 2 and 48, 2, ad 2; S. c. G. III, 9; De pot. 7, 2, ad 1;
De malo 1, 1, ad 19; Quodl. IX, 2, 2; De ente, c. 1; In
I Sent. 19, 5, 1; In II Sent. 34, 1, 1; In V Metaph., lect. 9.”
Aertsen then specifies, “Ens or esse (in this context
Thomas uses the terms indifferently) is said in two ways. In the first way it signifies
‘the entity of the thing according to its division by the ten categories’ (S.Th.
I, 48, 2, ad 2); ‘the essence of the thing or the act of being’ (De pot.
7, 2, ad 1); ‘the nature of the ten genera’ (De malo 1, 1, ad 19); ‘what
is divided by the ten genera, and so being signifies something existing in nature,
whether a substance, such as man, or an accident, such as color’ (In II Sent.
34, 1, 1); and ‘what is outside the soul (extra animam), divided by the ten
categories’ (In V Metaph., Lect. 9, 889). In a second way ‘being’ signifies
what is ‘only in the mind’ (ibid.); means ‘the truth of a proposition that exists
in a composition the mark of which is the verb “is”’ (S.Th. I, 48, 2, ad
2). And this text continues: ‘In this sense being is what answers the question “if
something is”’ (hoc est ens quo respondetur ad quaestionem ‘an est?’). Similarly,
in De malo 1, 1, ad 19: ‘being’ is said in a second way, ‘according as it
answers the “if” question.’”
“The reasons for this distinction [extra-mental being versus intra-mental being],” Aertsen emphasizes, “become
clear especially when attention is given to the problems it means to resolve.”
“What ‘is’ according to the first way,” Aertsen reports, “is also
‘being’ according to the second mode; for an affirmative proposition—e.g., ‘man
is’—can be formed about whatever has natural being. Yet the reverse is not the case.
Whatever is in itself a non-being, such as a privation, can be regarded as a being
by the intellect and affirmed in a statement—e.g., ‘evil is.’ This does not imply,
however, that evil is something in reality, that is, is according to the first mode
of ‘being.’”
The reference here is to In I Sent. 34, 1, 1; In V Metaph.,
lect.9, 896; De ente, c. 1.
“The possibility of affirming privations and negations,” Aertsen
continues, “is therefore a first reason to regard the answer to the question ‘if
it is’ as purely logical, predicative synthesis.”
“A still more important motive,” Aertsen underlines, “becomes
apparent at the beginning of the Summa theologiae. After Thomas in q. 1 has
shown that sacred doctrine is a science, he asks and affirms in the very first place
(q. 2), in conformity with the order of questioning: ‘if God exists’ (an sit
Deus). When it is subsequently inquired in q. 3, art. 4 whether ‘essentia’ and
‘esse’ are identical in God, then the objection arises (obj. 2): ‘We can
know ‘if God is,’ as has been explained above. ‘What He is,’ however, we cannot
know. Therefore there is a nonidentity between God’s being (esse) and his
essence (quod quid est eius).’ To this objection Thomas responds with the
dichotomy of ‘being’ just mentioned. It may mean the act of being, or it may mean
the composition of a proposition effected by the mind in joining a predicate to
a subject. Taking ‘being’ in the first sense, we cannot understand God’s being;
but only in the second sense.”
In the footnote Aertsen reports, “Esse dupliciter dicitur, uno
modo, significat actum essendi; alio modo, significat compositionem propositionis,
quam anima adinvenit coniungens praedicatum subiecto. Primo igitur modo accipiendo
esse, non possumus scire esse Dei, sicut nec eius essentiam, sed solum secundo modo.
Scimus enim quod haec propositio quam formamus de Deo, cum dicimus Deus est, vera
est.”
And then Aertsen continues, “This reply raises, however, various
questions. Let us have a closer look at it.”
“In the first place,” Aertsen reasons, “the objection suggests
that the ‘if’ and ‘what’ questions imply a composition of ‘being’ (esse)
and ‘essence’ in that which can be questioned. In 1.3.2., [of Aertsen’s book], however,
we saw that this questioning was, indeed, restricted to composed things, but then
to a thing that is characterized by the composition of form and matter. What would
have to be explained first, therefore, is how the order of the questions is related
to the composition of ‘esse’ and ‘essentia’ (cf. 1.9., [of Aertsen’s book]).”
“From this remark,” Aertsen contends, “there follows directly
a second point that is usually given too little consideration. The preliminary question
must be whether this mode of questioning is at all possible with respect to God.
Are the limits of this questioning not overstepped in the question ‘if God exists?’
For with regard to a simple being, there is no room for any question (1.3.2., [of Aertsen’s
book]).”
Aertsen then affirms that “After drawing this corollary in his
commentary on the Metaph. (VII, lect. 17, 1671), Thomas adds that what is
required here is another mode of questioning (alter modus quaestionis). For
we come to knowledge of simple substances only from the sensible ones, of which
the first are in a certain sense the causes. ‘Therefore we make use of sensible
substances as that which is known, and through them we inquire concerning the simple
substances.’ That is precisely the method that Thomas follows in his ‘ways’ to the
existence of God. It must, however, be realized that this mode of questioning is
not the ‘analysis’ of an inner composition but the reduction to the extrinsic cause
of sensible things. In Thomas’s reply the important structural difference between
the two modes of questioning is by-passed, so that the necessity arises to regard
the answer to the ‘if’ question as, simply, propositional truth.”
“Two considerations,” argues Aertsen, “evidently lead Thomas to
reduce the answer to ‘if’ question to something purely mental (Quodl. IX,
2, 2: tantum in actu animae componentis et dividentis), namely, the affirmation
of privations, which are not ‘something;’ and the affirmation of immaterial substances,
of which the being-something is unknown to us. With regard to both, it is accordingly
impossible to ask: ‘What is it?’”
“From this negative conclusion,” Aertsen contends, “there results
an important positive insight: as question, the ‘if’ cannot be separated from the
‘what’ ontologically. But this implies that in both the cases mentioned, the ‘if’
question fails to reach its end. The affirmation of negations and of immaterial
substances would therefore have to be distinguished expressly from an affirmation
in which the sense of the ‘if’ question is really fulfilled. Such is the case whenever
what is affirmed is not merely an accidental predicate, but means ‘being’ in the
first way, which is already connected with the ‘what’ question. One can affirm that
‘evil is’—insofar as answer is given to the ‘if’ question—but this does not mean
that evil is ‘something,’ because ‘being something signifies not only what answers
to the ‘if’ question but also what answers to the ‘what’ question’ (De malo
1, 1, ad 19). The sense of the ‘if’ question (an est) is to manifest the
subject as ‘ens,’ as ‘that which is,’ a substantial predicate, a ‘being something’
that has its sequel in the ‘what’ question” (J. A. Aertsen, Nature and Creature,
20-23).
We conclude by saying
that in the Summa theologiae, part I, question 3, article 4, ad 2, Aquinas
once again makes use of the res significata of the expression actus essendi
(a metaphysical principle) to explain his understanding of the several meanings of the verb esse.