Chapter 24 — That the divine being cannot be specified by the addition of any substantial difference

Again. From what we have said above, it can be shown that we cannot add anything to the divine being that specifies it by an essential specification (as a genus is specified by differences).

For it is impossible for a thing to be in act without also all those things by which its substantial being is specified, for an animal cannot be in act unless it be either a rational or an irrational animal. Therefore also the Platonists who postulated ideas did not postulate essentially existing ideas of genera, which derive specification from essential differences, but they postulated essentially existing ideas of the species alone, which do not need to be specified by essential differences. If, then, the divine being can receive an essential specification from something added to it, that being will not be in act without something added to it. But God’s very being is his substance as shown above. (Ch. 22.) Therefore, the divine substance cannot be in act without some addition, the contrary of which has been shown above. (Ch. 13.)

Again. Whatever needs something added to it, in order to exist, is in potency to that thing. But the divine substance is not in potency in any way, as proved above. (Ch. 16.) And God’s substance is his being. Therefore, his being cannot receive essential specification from something added to it.

Moreover. Whatever makes a thing to be in act, and is intrinsic to that thing, is either its whole essence or part of its essence. Now, that which specifies a thing by an essential specification makes a thing to be in act, and is intrinsic to the thing specified, otherwise the latter could not be specified essentially thereby. Therefore, it must be either the very essence or part of the essence of that thing. But if something is added to the divine being, it cannot be the whole essence of God, for it has already been proved (Ch. 22.) that God’s existence is not distinct from his essence. Therefore, it follows that it is a part of the divine essence: and thus God would be composed of essential parts, the contrary of which was proved above. (Ch. 18.)

Again. That which is added to a thing by way of essential specification does not constitute the notion of that thing, but only makes it to be in act: for “rational” added to “animal” makes animal to be in act, but does not constitute the notion of an animal as such, because the difference does not enter into the definition of the genus. Now if something be added to God to specify him with an essential specification, it must give that to which it is added the notion of its proper quiddity or nature, since what is added in this way gives the thing actual being. Now this (namely, actual being), is the divine essence itself, as shown above. (Ch. 22.) It follows, therefore, that nothing can be added to the divine being to give it an essential specification, as a difference specifies a genus.