The Refutation of All Heresies: Book VII. 6Nonentity as a Cause.

If, however, this animality is not any of these (species), the subsistence, according to Aristotle, of the things that are generated, derived its reality from non-existent entities. For animality, from whence these singly have been derived, is not any one (of them); and though it is not any one of them, it has yet become some one originating principle of existing things. But who it is that has established this substance as an originating cause of what is subsequently produced, we shall declare when we arrive at the proper place for entertaining a discussion of this sort.