Chapter 17 — That in God there is no matter

From this it follows that God is not matter. For matter, such as it is, is in potency.

Again. Matter is not a principle of activity. Hence, as the Philosopher puts it, efficient and material causes do not coincide. (Aristotle, Physics 2.7.) Now, as stated above, (Ch. 13.) it belongs to God to be the first efficient cause of things. Therefore, he is not matter.

Moreover. For those who referred all things to matter as their first cause, it followed that natural things exist by chance, and against these it is argued in Physics 2.8–9. Therefore, if God, who is the first cause, is the material cause of things, it follows that all things exist by chance.

Further. Matter does not become the cause of an actual thing except by being altered and changed. Therefore, if God is immovable, as proved above, (Ch. 13.) he can in no way be a cause of things as their matter.

The Catholic faith professes this truth, asserting that God created all things not out of his substance, but out of nothing.

The ravings of David of Dinant are confounded by this, who dared to assert that God is the same as prime matter, because if they were not the same, they would need to differ by certain differences, and thus they would not be simple, since in that which differs from another thing by a difference, the very difference argues composition.

Now this proceeded from his ignorance of the distinction between difference and diversity. For a thing is said to be different in relation to something, as is said in the Metaphysics, (Aristotle, Metaphysics 10.3, 1054b23–32.) because whatever is different differs by something, whereas things are said to be diverse absolutely from the fact that they are not the same thing. (ST I.3.8, ad 3.) Accordingly, we must seek for a difference in things which have something in common, for we have to point to something in them whereby they differ: thus two species have a common genus from which they must be distinguished by differences. But in those things which have nothing in common, we do not have to look for their differences, for they are diverse by themselves. For thus are opposite differences distinguished from one another, because they do not participate in a genus as a part of their essence. Consequently, we must not ask in what they differ, for they are diversified by their very selves. Thus too God and prime matter are distinguished, since they have nothing in common, the one being pure act and the other pure potency.