Commentaria in Summam contra Gentiles, Liber I

Finally, Saint Thomas excludes from God the composition of genus and difference ¹. In this matter he does two things: first, he excludes potential composition, insofar as a genus contains many differences potentially, by which it can be determined; second, actual composition, insofar as a species is said to be composed of genus and difference ².

I. As to the first, the following conclusion is proposed: Nothing can be superadded to the divine esse that would designate it by an essential designation, in the way a genus is designated by its differentiae.

For the understanding of this, before the conclusion is proved, it must be considered that a genus is said to be designated or determined essentially by its differences—not as if those differences were part of the essence and quiddity of the genus, but because they divide the nature of the genus into diverse essences and natures contained per se under that genus. For the genus signifies a certain nature unlimited and indeterminate with respect to the species; by the addition of one difference it is contracted to one species, of which it is predicated essentially, and by the addition of another it is contracted to another species; and thus it is said to be designated by an essential designation, that is, to be determined to the essence of a species contained per se under it. In this way, then, designation is denied of divine esse, namely on the ground that it is something common, signifying a certain indeterminate nature, limitable by some difference and contractible to a more particular nature contained per se under it—as some have wrongly held.

It is proved, first. God is of himself necessary being (esse). Therefore his essence is not in any supervening act. Therefore neither is his esse. Therefore his esse is not designated by essential designation. — The first consequence is evident. — The second is proved, because his esse is his essence. — The third, however, because it is impossible for anything to be in act unless all the existents by which substantial esse is designated exist: for an animal is not in act unless it be rational or irrational. Nor did even the Platonists posit ideas except of the most special species. Therefore, if esse were designated by essential designation, it could not be in act except through that which would designate it. And thus it would be in act through something supervening.

2. Concerning Plato's position, it must be noted that the phrase most special species does not make a distinction from all universals simply, for, as is clear from I Ethics ³, and as is held by St. Thomas in Prima, q. vi, a. 4, and On Truth, q. xxi, a. 4, Plato posited not only ideas of most special species but also of being, of one, and of good; but it does make a distinction from subordinate species, namely from genera. For as is said in Truth, q. iii, a. 8, Plato did not posit ideas of genera but only of most special species, because, since an idea belongs only to those things that are intended per se, and the intention of nature is not terminated at the production of the form of a genus but only at the form of a species, it was not necessary to posit ideas of genera, though it was fitting to posit ideas of species. Hence when St. Thomas sometimes says ⁴ that Plato held that things which can be separated according to intellect are separated according to esse, this must be understood of those things that are intended by nature per se. Now such are most special species, and those things common to all, such as being, one, and good; but not genera.

3. It must be noted that this proposition, It is impossible for anything to be in act unless all those things exist by which substantial esse is designated, can be expounded in two ways. In one way, so that by "substantial esse" we understand the very essence and quiddity. And thus it is without doubt true, as is shown by the example and Plato's position: for an animal cannot be in act unless there exist the differences by which the nature of animal is determined to one species not further determinable essentially. But that sense does not seem relevant to the point at issue: for here Saint Thomas is speaking of the actual existence of God, not of essence.

Therefore it can be understood in a second way, so that by substantial esse is understood the very actuality of being. And then the proof can be expounded in two ways: namely, by way of similitude, and by way of example. By way of similitude: because, just as an animal cannot exist in act unless its limiting difference exists essentially, so, if esse receives its essential limitation from something else, it cannot be posited in act unless that difference by which it is essentially limited exists. — And also by way of example: since an animal is not in act unless there is some difference of it by which its substantial esse is determined. Therefore, similarly in all other things, nothing is in act unless all those things by which substantial esse is essentially determined exist. But how substantial esse is determined by rational or irrational will be said in the third argument ⁵.

II. But a doubt arises. For it does not seem unfitting that the divine essence be in act through something superadded, if that thing is not really distinct from the essence: just as it is not unfitting that one be wise through a wisdom superadded to the essence, which is not really distinct from it but distinct only according to reason. For this does not take away that one is wise through oneself; just as the fact that one is wise through wisdom does not take away that one is wise through oneself and through one's essence. Now, if something were added to the divine esse determining it essentially, that thing would be really distinct neither from the esse nor from the essence: just as the difference contracting a genus is not really distinct from the genus. Therefore it is not unfitting that the essence itself be in act through something superadded to it.

For the clarification of this doubt, it must be considered that we must speak in one way of the nature of the genus as it is in the species according to the thing itself, and in another way as it is considered in common through abstraction from the species and differences. In the first way, it is really identical with the difference, and the difference is not something added to the entity of the genus. In the second way, however, the genus is considered as formally distinct from the difference, having with it no identity except a potential one, namely that of containment, insofar as it contains those differences potentialiter. Therefore the difference is then considered as wholly outside the essence of the genus. And therefore, when the difference is added to the nature of the genus so considered, it is added as something extraneous to the essence of the genus. Hence, if the genus were posited to exist as it is understood, it would be without the differences by which it is divided and contracted to its inferiors. For it is evident that animal, considered through abstraction from the differences, is essentially nothing other than substantia animata sensibilis; and if rationale is added, it will be called substantia animata sensibilis rationalis, wherein it is clear that rationale is added to the whole essence of animal. And thus, for animal to be, it is required that something be added to it which lies outside its formal ratio, even though in that which is constituted by them, genus and difference are really the same. Hence it cannot be said that the genus is through itself, but through another: namely, through the difference.

Thus, therefore, if the divine esse, considered formally and according to its proper ratio, were something common and essentially contractible in the manner of a genus, and likewise if the divine essence could not actually be except through something wholly alien to its quiddity and essence, formally considered—although that added to the essence, in that thing in which it would be united, would be really identical with the essence.

It is said, therefore, in reply to the doubt that it is not only unfitting that the divine essence should need, for its actual esse, something really distinct from itself; it is also unfitting that it should need anything outside its formal ratio and quiddity: for then it would not be necessary in being from its own quiddity and essence, but would need something wholly extrinsic to its formal and quidditative ratio in order to be.

What is added, however, concerning wisdom is not similar. For wisdom is not outside the formal and quidditative account of the essence, if the divine essence were considered as it is in itself, but only insofar as it is conceived by us in various ways. But if the divine essence were a nature indeterminate in the manner of a genus, and were determined by an essential difference, that difference would be outside the quidditative account of the essence even considered as it is in itself, and not merely according to our manner of conceiving it.

III. Second. The divine substance is in no way in potency: * because it is ipsum esse itself, which is most actual. Therefore the divine esse cannot be signified essentially by something added to it.* — The consequence is proved. Because everything that needs something in order to be is in potency with respect to it: * namely, if it needs it as a limiting form*.

IV. Third. It is designated essentially by something added. Therefore that added element makes the designated thing be in act, and is intrinsic to it. Therefore it is either its essence or a part of its essence. It cannot be the whole essence of God: for His essence is the same as esse; but what is added to esse is not the whole esse, insofar as it is added, although materially it could be the same esse. Therefore it is a part of the essence. Therefore God is composed. The opposite of this was shown above. — The first inference is proved: because what designates something by essential designation makes the thing be in act, and is intrinsic to the designated thing. — The second is also proved: because that by which a thing is in act and which is intrinsic to the thing is either the whole essence or a part of the essence.

Note that this argument proceeds from the imagination that something is added to the divine esse as constitutive of the divine essence, just as something is added to a genus that is constitutive of the species.

But concerning that proposition, That which designates something by essential designation makes the thing be in act, and is intrinsic to the thing designated, it must be known that being in act can be taken in two ways: in one way, in quidditative and essential act; in the other way, in the act of actual existence. This proposition is understood not only of being in quidditative act, but also of being in the act of existence. For this rational difference, added to animal, constitutes man—who is here called the designated thing—in the act of essence and quiddity: because man was contained in animal potentially, and by the addition of the difference there is constituted in act rational animal, which is the essence and quiddity of man; just as by the conjunction of form with matter the whole itself is made in quidditative act. It also constitutes man in actual existence: insofar as it constitutes the quiddity, which is the proper recipient of esse, formally speaking and essentially. For from the addition of the specific difference to the genus there is constituted, essentially, the proper recipient of esse: because the most special species does not need any intrinsic formal principle in order to be, although in material things certain material principles individuating the nature are required. On account of this Porphyry says, ⁶ that the difference contributes to esse: namely, because it constitutes its essential recipient.

V. Fourth. If something were added to the esse of God, it would be added to His essence: because essence and esse in Him are the same. Therefore that which designates essentially would constitute the proper account of the divine nature and quiddity. But this is contrary to the account of what essentially determines something: for nothing of that sort constitutes the account of that to which it is added, just as rational does not constitute the account of animal. -- The consequence is proved as follows. What is added in this way constitutes the esse in act of that to which it is added. But in God this is the divine essence. Therefore, if something were added to Him essentially, it would constitute His essence.

Concerning that proposition, That which is added to something to designate it essentially does not constitute its ratio, but only its esse in actu, it must be noted that this proposition is not the same as the proposition of the preceding argument which we expounded ⁷. For in the latter, esse in actu was referred to what is constituted by genus and difference, or to what is constituted by an addition and that to which the addition is made—which was called the designated or determined thing, that is, including the very determination itself—but not as that to which designation is applied from without. Here, however, it is referred to that to which the addition is made, or to the genus itself. For the genus, because it has the character of potency and determinability, when considered under the aspect of the universal whole, does not have within itself anything in act of those things by which it is determined to species. Therefore it is in potency with respect to the differences and species. But through the addition of a difference it comes into act as difference and species, and becomes the proper essential subject of actual existence: just as matter, because it has no act in its own substance if considered with all form abstracted away, is in potency so as to be determined to this or that form and to this or that species; but once it has received a form, it is in act of that form and of the species constituted by it, and in the esse of actual existence, which accompanies that form.

VI. For a fuller understanding of what has been said in this chapter, it must be known, from the teaching of St. Thomas in the Prima, q. iv, a. 1 ⁸, the de Pot., q. vii, a. 2, and the de Ente et Essentia ⁹, that one must speak differently of esse of actual existence abstracted according to the thing, such as divine esse is, and differently of esse abstract and common according to the concept: just as one would speak differently of whiteness if it were separated according to the thing from every receiver, and differently if it were abstracted from every subject only by consideration. They do indeed agree in this, that esse abstract according to the thing and esse abstract according to the concept are both indeterminable by a formal difference: because esse names the most perfect act and the actuality of all actualities, and consequently nothing is more formal and more actual than esse itself; from which it follows that nothing is added to either the one or the other, otherwise it would not be altogether abstract; just as to animal, considered by abstraction from all differences, no rational difference is added. But they differ in this: that divine esse, separated according to the thing from every receiver, cannot be determined not only by an essential difference but not even by any receptive subject, since it can be received in nothing: just as a whiteness that were really separated from every subject could not be received in a subject, for it would be distinguished from this and that particular whiteness because it would subsist as separated from every subject, whereas the others exist in this or that subject; hence, if its subsisting and separate character were removed from it, it would no longer be the same as before. But esse common according to the concept, although it cannot be limited by formal and essential differences, can nevertheless be determined by diverse receivers: for the esse of man comes about because it is received in human nature, and the esse of horse because it is received in the nature of horse; just as whiteness, common according to the concept, is limited to this and that because it is received in this and that subject. Therefore divine esse, although it is absolute from every determining principle, is nevertheless not esse common according to the concept: because esse common according to the concept, although as such it is not determined in act by anything, can nevertheless be determined by a receiver; but divine esse is determined neither in act nor in potency—indeed, it belongs to its very nature that it cannot be determined.