Cursus Philosophicus Thomisticus, Secunda Pars Artis Logicae

We treat those things that are placed in the direct line of this category by participating in the account of the highest genus and contracting it.

AND WE SAY BRIEFLY that two conditions are required for a substance to be placed in the direct line and to be a categorial substance. First, it must be a finite substance; second, it must be a complete substance, that is, one to which the property of subsisting and underlying belongs per se. It belongs per se to what is signified as a whole. A part does not possess it per se, but through another and dependently on another, that is, on the whole. From the inclusion or exclusion of these conditions we shall understand which substances are placed in the account of this category and which are excluded from it.

Both conditions are gathered from a single principle: a categorial substance must not merely be a subsistent being; it must also be composite, so that it subsists through some composition. THE REASON IS that an infinite substance, if placed in a category, cannot be placed there as the highest genus, but only as something contained under such a genus. For if it were the highest genus, all categorial substances participating in that genus would be infinite. It must therefore be a species and consequently consist of genus and difference, for this is what is called a species. But genus expresses something potential, which is related to differences as something contractible and determinable by them. Therefore God would consist of one account expressing potentiality and another expressing actuality, and thus would not be pure act, since he would have something potential, namely the account of genus. Hence the actuality expressed by the specific difference would not be pure act either, since it would be joined to a potential actuality, namely the genus. That such a genus would express potentiality is clear, besides what was said in the question on genus¹, because genus cannot be pure act: if it were, it would not be determinable and contractible by differences, which actualize and qualify the genus they contract. Pure act, however, is in ultimate actuality. Moreover, since that genus would be common to God and creatures, and pure act is not found in creatures, it is consequently not pure act in itself. A composition of act and potency is therefore required for something to be a categorial substance; this is incompatible with an infinite substance, that is, pure act.

FROM THE SAME PRINCIPLE THEY EXCLUDE incomplete beings, for example, difference—not because they express pure act, but because they exclude composition from genus and difference. For if they were composed, that difference in turn would be composed of genus and difference, since the same reasoning applies; that difference in turn would be composed of another, and so there would be an infinite regress, requiring infinitely many compositions to compose one quiddity. Again, if the same genus that is genus with respect to a species were also genus with respect to a difference, genus would be placed twice in the definition, once on account of the species and again on account of the difference. Nor could it be univocal, since it would belong to the concept of differences and express the account of diversity, as we proved above in the discussion of analogues.² Therefore it is incompatible with differences being directly in a genus; they are instead reduced to it and placed, as it were, alongside it.

Whether matter, form, and integral parts as such are directly contained under the genus of substance, we said in the question³ on genus, article 3. It suffices now to add that insofar as parts do not underlie, neither do they subsist directly, but dependently on the whole. Therefore they are not per se and directly substance, since what is directly substance is what directly calls for subsisting and underlying, which belongs only to the whole, whether taken singularly or in common. Thus universal substance per se calls for subsisting, but exercises this as it exists in an individual. Parts, however, call for subsisting and underlying not per se, but through and in the whole, as I now presuppose from the Metaphysics. Likewise, since the parts of substance are per se and intrinsically ordered to composing the whole, which is directly placed in the category, if the parts themselves were also directly placed in the category, the same thing would be placed in the category and in the definition twice, once on its own account and again on account of its parts. We said the same concerning difference; the Philosopher does not allow this absurdity in Metaphysics 3, text 10⁴, nor does St. Thomas there⁵ or in Contra Gentiles 1, chapter 25.

BUT YOU WILL OBJECT: Some composition by reason, and consequently something by way of potency and act according to our consideration, is not incompatible with God, as certain authors hold. For our intellect distinguishes the divine perfections, even though they are one most simple reality. Therefore our mode of conceiving can conceive these perfections and attributes by way of act and potency.

Hence this is confirmed: if division according to our mode of conceiving is not incompatible with pure act, composition will not be incompatible with it either, since the same reasoning applies to opposites.

But this objection presupposes something impossible: that a distinction in God can be conceived by excluding and separating one thing from another. This cannot stand, because, since God is pure act, the very conception of something in him as potential and as added to something else destroys the concept of pure act. Therefore what occurs here is not abstraction but destruction of one attribute by another. For when an attribute in God is conceived, it is conceived either as divine being, as created, or as abstracting from both. If as created or as abstracting, it is not conceived as pertaining to God or as something of God, and so is destroyed. If as uncreated, then it is conceived as pure and infinite act, and therefore as excluding all potentiality, even as a subject of such a concept. Thus this distinction in divine things does not occur by excluding one perfection from another, but through an implicit or explicit concept. Our imperfect mode of conceiving explains one perfection in God without explaining another. This explaining of one and not explaining of another is a distinction of reason, which can occur in God; but it is not a concept of one perfection as formally excluding another and standing in potency to it, since every concept of potentiality is incompatible with the account of pure act. Hence such division is not opposed to composition, but to a perfect explanation of the same most simple reality. Composition of reason, founded on the potentiality of one extreme and the addition of another to it, therefore does not belong to God; rather, there is a greater or lesser explanation of the same thing, as was said of the transcendentals in the preceding question.⁶

SOME DOUBT ABOUT THE LORD CHRIST as to whether he is placed in a category by reason of his human nature, or insofar as he is man. It must be asserted without qualification that he is, because, as the faith teaches, he is univocally man, subsisting from a rational soul and human flesh. Therefore he is placed under the species of man, since he is placed univocally under man and consequently under living animal, and so forth. This is to be placed under a genus and species, and thus in the levels of a category.

NOR IS IT AN OBJECTION that only created being is in a category, whereas Christ is not absolutely a creature, as St. Thomas teaches in 3. p. q. 16. art. 8.; therefore he is not absolutely placed in a category. The answer is that the accounts differ, because the name “creature” is indifferent as to whether it designates a nature or a supposit, on account of its transcendence. Being in a category, however, belongs only by reason of a nature, which in Christ is created insofar as he is man, just as walking and dying belong to him by reason of his nature.

From these points it is clear that every created substance is contained in this genus, even if incorruptible and spiritual. For it is finite and composite, at least of some potency and act, since it is not pure act. Therefore some determinable and contractible account, and some determining and contracting account, can be conceived; consequently, it must pertain to some genus and category, and there is no other than this one. Since these are complete and integral substances, not merely incomplete beings, as is clear in the case of angels, they consequently belong directly and not reductively.

When the Philosopher says in Metaphysics 10, final chapter⁷, lecture 12⁸ according to St. Thomas, that “the corruptible and incorruptible differ in genus,” he is speaking of physical genus, which is matter. The meaning is that they do not agree in matter: on the more probable opinion, the heavens have matter specifically different from that of sublunary things, and angels have none.