Of God and His Creatures

In the scholastic theory, materia prima, or primordial matter, is never found, as the chemistry books speak, 'free,' but always in composition with some form or another: it cannot be 'isolated.' Still no one form can be mentioned with which it must be compounded, if it is to be at all. If I must eat fruit, I need not eat peaches.

Of God and His Creatures: 3.5