Then he presented a question and answer whose substance was this: corporeal substance subsists only through its nature, which in turn subsists through the motion specific to it.

He said:

“If someone supposes that, when its natural form is assumed to have ceased to exist, this substance dissolves into something simpler, whose nature possesses no motion specific to it, then this simpler thing would not itself be an effect, although the composite containing it would be an effect.

“Aristotle says that this supposition is false and impossible, for that simple thing would then exist only in thought. In its own right, taken in isolation, it has no real existence and does not subsist in itself.

“This is not the only ground on which he rejects this supposition. He also holds that the simple thing into which corporeal substance dissolves in thought, when we conceive of that form as perishing, possesses a receptivity to another form. In respect of this receptivity, it is therefore an effect of the first mover.

“If someone supposes that it is an effect only in respect of this receptivity, we say: if we suppose that this very receptivity is removed—that it ceases to exist—then its essence must cease to exist. That is, its nature, by which it is then what it is, must perish and dissolve, since its essence at that point is precisely that which is receptive by nature.

“If it is further said that it dissolves into something else, the answer would be the same as our answer concerning the first dissolution. This process of dissolution cannot continue indefinitely.”

He said:

“It is thus clear that every corporeal substance is, in its substance, existence, and continued subsistence, an effect of the cause that is the first principle of the motion of all things.”

I say: This, then, is their argument for the existence of the first cause, which is the principle that