Medieval Philosophy

by Peter S. Adamson

The difficulty of accounting for the shared features of things is called the problem of universals. Perhaps the most famous attempt to answer the problem is also the earliest attempt: Plato’s theory of Forms. This theory was apparently intended to explain common characteristics like humanity or largeness by postulating a single, overarching Form or paradigm, humanity-itself or largeness-itself. And readers have traditionally understood Plato’s Forms as universals. This may not be quite right, though. Aristotle points out that although a Platonic Form does play the role of a universal by accounting for shared membership in a kind of thing, it also seems to be just another kind of particular, albeit a perfect, unchanging, and paradigmatic particular.1 In fact it was Aristotle himself who really started talk of “universals” in philosophy. Unfortunately, he left it rather unclear what sort of metaphysical status we should assign to a universal like humanity or animality. For this reason, ancient commentators on Aristotle already engaged in detailed discussions of the problem of universals, discussions that were passed on to the medievals thanks to the translations and commentaries of Boethius. For Boethius and his medieval heirs, the starting point for discussion of this problem was the beginning of Porphyry’s widely read Introduction to Aristotelian logic.2 In a few sentences that rank as one of the most enticing but unsatisfying passages in the history of philosophy, Porphyr...