In the Summa, Aquinas frequently invokes (for lack of a better term) certain "logical-metaphysical presuppositions." Here are two examples drawn from I-II, qq. 90-91:
- "that which is the principle in any genus, is the rule and measure of that genus"
- "in every genus, that which belongs to it chiefly is the principle of the others"
Sometimes he gives justification for these kinds of presuppositions, and other times he doesn't. But in both cases they seem rather ad hoc, as if constructed on the fly to fill in logical gaps. Where is Aquinas getting these? Is he simply drawing them from Aristotle, or is he working with a formal set of presuppositions that were well-established in the 13th century? Reading suggestions on this topic would be much appreciated.