Chapter 16 — That in God there is no passive potency

Now if God is eternal, it follows of necessity that he is not in potency.

For everything in whose substance there is an admixture of potency is possibly nonexistent as regards whatever it has of potency, for that which may possibly be may possibly not be. Now God in himself cannot not be, since he is eternal. Therefore, in God there is no potency to be.

Again. Although that which is sometimes potential and sometimes actual, is in point of time potential before being actual, nevertheless act is simply before potency, because potency does not bring itself into act, but needs to be brought into act by something actual. Therefore, whatever is in any way potential has something previous to it. Now God is the first being and the first cause, as stated above. (Ch. 13.) Therefore, in him there is no admixture of potency.

Again. That which of itself must necessarily exist can in no way have possible existence, since whatever of itself must necessarily exist has no cause, whereas whatever has possible existence has a cause, as proved above. (Ch. 15.) Now God, in himself, must necessarily exist. Therefore, he can in no way have possible existence. Therefore, no potency is to be found in his essence.

Again. Everything acts according as it is actual. Therefore, that which is not wholly actual acts not by its whole self, but by part of itself. Now that which does not act by its whole self is not the first agent, since it acts by participation of something and not by its essence. Therefore, the first agent, which is God, has no admixture of potency, but is pure act.

Moreover. Just as a thing is naturally apt to act insofar as it is actual, so is it natural for it to be passive insofar as it is in potency, for movement is the act of that which is in potency. (Aristotle, Physics 3.1, 208a27–28.) Now God is altogether impassible and immovable, as stated above. (Ch. 13.) Therefore, in him there is no potency, namely that which is passive.

Further. We notice in the world something that passes from potency to act. Now it does not reduce itself from potency to act, because that which is potential is not yet; hence, neither can it act. Therefore, it must be preceded by something else by which it can be brought from potency to act. And if this again passes from potency to act, it must be preceded by something else, by which it can be brought from potency to act. But we cannot go on thus to infinity. Therefore, we must come to something that is wholly actual and in no way potential. And this we call God.