Entry 0386: Commentary on
In I Sententiarum, distinction 8, question 4, article 2, ad 2
The question asked in this article is whether or not God belongs to the category of substance. In a rather unusual way in this article, Aquinas does not structure his answer in a corpus. Rather, after granting the argument of the second sed contra, Aquinas gives his explanation within the segment of the sed contra.
In the second sed contra Aquinas uses the axiom quidquid est in genere habet esse suum determinatum ad illud genus and the premise that the divine esse transcends all categories—divinum esse nullo modo terminatum ad aliquod genus—to conclude that God does not belong to the category of substance. The explanation of the validity of the sed contra is formulated in four reasons—ratio quadruplex assignatur. Of these, only one argument interests us here, the ratio subtilior which Aquinas attributes to Avicenna.
Here is the text:
“Tertia ratio subtilior est Avicennae. Omne quod est in genere, habet quidditatem differentem ab esse, sicut homo; humanitati enim ex hoc quod est humanitas, non debetur esse in actu; potest enim cogitari humanitas et tamen ignorari an aliquis homo sit. Et ratio hujus est, quia commune, quod praedicatur de his quae sunt in genere, praedicat quidditatem, cum genus et species praedicentur in eo quod quid est. Illi autem quidditati non debetur esse nisi per hoc quod suscepta est in hoc vel in illo. Et ideo quidditas generis vel speciei non communicatur secundum unum esse omnibus, sed solum secundum unam rationem communem. Unde constat quod esse suum non est quidditas sua. In Deo autem esse suum est quidditas sua aliter enim accideret quidditati, et ita esset acquisitum sibi ab alio, et non haberet esse per essentiam suam. Et ideo Deus non potest esse in aliquo genere” (In I Sententiarum, distinction 8, question 4, article 2, sed contra 2).
Aquinas begins by stating that in everything that belongs to the genus of substance one finds the real distinction of quidditas and esse. If one takes for example man—homo—, one does not need to know of the existence of some man to reason conceptually about the quiddity of man—humanitas. This is so, Aquinas argues, because the common concept that is predicated of many things in a genus is the quiddity. A quiddity exists in the real world only when it is received in this or that other individual thing. Therefore in a genus, the quiddity is not communicated to many individuals according to one esse but according to the consideration of the intellect which considers a nature like that of man, without referring to Socrates and Plato. Thus Plato and Socrates have in common the nature of humanity but the esse of Plato’s humanity and the esse of Socrates’s humanity are numerically different. God, however, does not instantiate a quidditas different from His esse since, in God, esse actu is His quiddity. God therefore is not in the category of substance.
With this background Aquinas proceeds to analyze a definition of substance which was used in the second objection to answer the question in the affirmative. The authority of Avicenna is invoked again, but according to John F. Wippel the attribution of this definition of substance to Avicenna is likely to be a quotation ad sensum and not ad litteram, since the exact text has not been found in Avicenna’s writings. (1) The definition is this: “substance is that (ens) which does not inhere in a subject, but which exists in itself (ens per se).” And the second objection contends that this definition applies most fittingly to God. Therefore, God is in the genus of substance.
The Latin text of the objection reads as follows: “Praeterea, substantia est quod non est in subjecto, sed est ens per se. Cum igitur Deo hoc maxime conveniat, videtur quod ipse sit in genere substantiae” (In I Sententiarum, distinction 8, question 4, article 2, objection 2).
In his answer, Aquinas argues that this definition cannot be the definition of substance because, on the one hand, ens is not a genus and, on the other hand, the negation expressed with the phrase “does not inhere in a subject,” that is, substantia inquantum praedicatur non ut in subiecto existens, adds nothing that can be considered part of a definition since a pure negation cannot serve as a genus. It is at this point that Aquinas introduces the term “actus essendi” to accentuate the contrast between the meaning of the notion of “genus” and the meaning of the notion of “ens:”
“A genus does not signify esse, a genus signifies the quiddity.”
“Ens does not signify the quiddity, ens signifies the actus essendi.”
Thus, when addressing the passage from “ens which does not inhere in a subject” to “therefore it is in the genus of substance, Aquinas concludes with a simple non sequitur.
Thus Aquinas writes in In I Sententiarum, distinction 8, question 4, article 2, ad 2:
“Ad secundum dicendum, quod ista definitio, secundum Avicennam, non potest esse substantiae: substantia est quae non est in subjecto. Ens enim non est genus. Haec autem negatio ‘non in subjecto’ nihil ponit; unde hoc quod dico, ens non est in subjecto, non dicit aliquod genus: quia in quolibet genere oportet significare quidditatem aliquam, ut dictum est, de cujus intellectu non est esse. Ens autem non dicit quidditatem, sed solum actum essendi, cum sit principium ipsum; et ideo non sequitur: est non in subjecto: ergo est in genere substantiae. Sed hoc Deo non convenit, ut dictum est.”
Commenting on this text J. F. Wippel explains that “Thomas appeals to a point we have already seen him make in other contexts: whatever is included in a genus must signify a quiddity which does not include the act of being (esse) in its intelligible content. In fact, the term being (ens) does not signify quiddity but rather the act of being (actus essendi). Therefore it does not follow that if something is not in a subject, it is included in the genus of substance. What does follow is this. If something has a quiddity to which it belongs to exist not in a subject, then it is included within the genus of substance. But this (to have a quiddity to which it belongs to exist not in a subject) is not true of God. Therefore God does not fall within the genus substance” (The Metaphysical Thought of Thomas Aquinas, 230).
For more on the definition of substance see J. F. Wippel, The Metaphysical Thought of Thomas Aquinas, 228-237; and Jorgen Vijgen, The Status of Eucharistic Accidents “sine subiecto” (
: Akademie Verlag, 2013) 181-184. Berlin
Two things are worth noting regarding the use of the term “actus essendi” in this passage. First, that the text containing the term “actus essendi” is inserted in a context in which Aquinas is referring exclusively to the quiddity of the substance, not to the quiddity of accidents. And more importantly, second, that the three terms “esse,” “ens,” and “actus essendi” appear in the same text. How do these three terms relate to each other?
Concerning the res significata and the ratio significata of the term ens, there is no room for doubt. Aquinas says explicitly that ens non dicit quidditatem sed solum actum essendi. And from the way Aquinas explains the difference between the notion of “genus” and the notion of “ens,” it is clear also that the ratio significata of the term esse is the intellectual conception of the actus essendi, for he says that in quolibet genere oportet significare quidditatem aliquam de cujus intellectu non est esse.
Thus in this text again, it is indicated that the three terms “esse,” “ens,” and “actus essendi” have the same res significata, namely, the metaphysical principle of actus essendi. The term “ens” differs from “esse” and “actus essendi” in that it has a different ratio significata; the term “ens” responds to a modus inelligendi of the metaphysical principle of actus essendi that is different from the modus intelligendi of the metaphysical principle of actus essendi to which the terms “esse” and “actus essendi” respond.
(1) J. F. Wippel writes: “[A]s Gilson has pointed out in an interesting article, almost from the beginning of his career Thomas repeatedly returns to a point which he also attributes to Avicenna: being in itself (per se) is not the definition of substance. … Gilson has managed to show that there is some foundation in the Latin translation of Avicenna’s Metaphysics for Thomas to attribute this view to him. Even for this attribution to be successful, one must concede that “not to be in a subject” (or better, “to be not in a subject”) can be identified with “to be in itself.” Gilson’s identification and interpretation of this particular passage from Avicenna is highly plausible. If correct, it is another illustration of how likely Thomas was to quote a difficult and possibly confusing text from the Latin Avicenna ad sensum rather than ad litteram” (The Metaphysical Thought of Thomas Aquinas [Washington, D.C.: Catholic University of America Press, 2000] 229-230).