Alexander of Aphrodisias (fl. A.D. c.200), Greek philosopher, one of the foremost commentators on Aristotle in late antiquity. He exercised considerable influence on later Greek, Arabic, and Latin philosophy through to the Renaissance. On the problem of universals, Alexander endorses a brand of conceptualism: although several particulars may share a single, common nature, this nature does not exist as a universal except while abstracted in thought from the circumstances that accompany its particular instantiations. Regarding Aristotle’s notorious distinction between the ‘agent’ and ‘patient’ intellects in On the Soul III.5, Alexander identifies the agent intellect with God, who, as the most intelligible entity, makes everything else intelligible. As its own self-subsistent object, this intellect alone is imperishable; the human intellect, in contrast, perishes at death. Of Alexander’s many commentaries, only those on Aristotle’s Metaphysics A– d, Prior Analytics I, Topics, On the Senses, and Meterologics are extant. We also have two polemical treatises, On Fate and On Mixture, directed against the Stoics; a psychological treatise, the De anima (based on Aristotle’s); as well as an assortment of essays (including the De intellectu) and his Problems and Solutions. Nothing is known of Alexander’s life apart from his appointment by the emperor Severus to a chair in Aristotelian philosophy between 198 and 209. See also ARISTOTLE , CONCEPTUALISM , STOICIS. V.C.