In Search of Aristotle’s Third Man

Abstract Aristotle thinks that the Platonic theory of Forms is vulnerable to the Third Man regress. According to Alexander of Aphrodisias, the regress arises from the conjunction of three Platonist claims, which I label ‘Exemplification’, ‘Similarity’, and ‘Distinctness’. It is clear why, taken together, these three claims generate an infinite regress of Forms. What is not clear is why Aristotle thinks that a Platonist should have to accept each of the claims. My answer begins from the fact that, in Metaphysics A and M, Aristotle mentions the Third Man as a consequence, not of positing Forms, but of certain ways of arguing for Forms. By working out what these arguments are likely to have been, we can understand why he took the Platonist to have been committed to all three claims, and thus why he saw the Third Man as a serious difficulty.