The men who introduced this doctrine did not posit Ideas of classes within which they recognized priority and posteriority (which is the reason why they did not maintain the existence of an Idea embracing all numbers); but things are called good both in the category of substance and in that of quality and in that of relation, and that which is per se, ie substance, is prior in nature to the relative (for the latter is like an offshoot and accident of what is); so that there could not be a common Idea set over all these goods.