Sextus Empiricus Pyrrhoniae Hypotyposes 2.20.226

[226] nor yet can it be some of them actually and some only potentially —corporeal, for instance, actually and incorporeal potentially. For it is potentially that which it is capable of really being actually, but that which is actually corporeal is incapable of becoming incorporeal in actuality, so that if, for example, the genus ‟something” is actually corporeal it is not potentially incorporeal, and vice versa. It is impossible, therefore, for the genus to be some things actually and some only potentially. But if it is absolutely nothing actually, it has no substantial existence. Hence the genus, which they say they divide into the species, is nothing.