FUNDAMENTAL UNITY OF GENERA WOULD DESTROY SPECIES; MANIFOLDNESS MUST PRE-EXIST.
Now that we have explained the existence of genera, which, besides, are principles of being, and that from another point of view there are principles (or elements), and compounds, we shall have to set forth the criterion by which we constitute these genera; we shall have to ask how they may be distinguished from each other, instead of reducing them to a single (principle), as if they had been united by chance, although it does indeed seem more rational to reduce them to a single (principle). It would be possible to reduce them in this way if all things were species of essence, if the individuals were contained within these species, and if there were nothing outside of these species. But such a supposition would destroy the species—for such species would no longer be species, or forms;—and from that moment there would be no further need for reducing plurality to unity, and everything forming a single unity; so that, all things belonging to this One, no being outside of the One would exist, as far as it was something else.
How indeed could the One have become manifold, and how could it have begotten the species, if nothing but it existed? For it would not be manifold if there were not something to divide it, such as a size; now that which divides is other than that which is divided. The mere fact that it divides itself, or imparts itself to others, shows that it was already divisible before the division.