Chapter 71 — That diversity of matter is not the cause of diversity in things

The foregoing exposition shows clearly that the cause of diversity in things is not diversity on the part of matter. For, as we have proved, the divine action which brings things into being does not suppose the preexistence of matter. The cause of diversity in things could not be on the side of matter unless matter were needed prior to the production of things, so that the various forms induced would follow diversity in the matter. Therefore, the cause of diversity in the things produced by God is not matter.

Again, things have unity and plurality according as they have being, for a given thing, inasmuch as it is a being, is also one. But forms do not possess existence for the sake of matter; rather, matter receives existence for the sake of form. For act is better than potency; and that for the sake of which something exists must be better than it. Therefore, neither are forms diverse in order that they may befit various types of matter, but rather diverse matters were established so that they might befit diverse forms.