Propter quod est unumquodque, et illud magis, a favourite saying of the schoolmen, answering to some such Aristotelian Greek as di ou hekaston, kakeino mallon. To defend the saying, we must have at hand distinctions between 'cause' (causa per se) and 'occasion' (causa per accidens); also between having an attribute 'virtually and in a better way' (eminenter) and having it 'precisely in this form' (formaliter).

Of God and His Creatures: 3.17