abstract:The Isagoge () or "Introduction" to Aristotle's "Categories", written by Porphyry in Greek and translated into Latin by Boethius, was the standard textbook on logic for at least a millennium after his death. It was composed by Porphyry in Sicily during the years 268-270, and sent to Chrysaorium, according to all the ancient commentators Ammonius, Elias, and David.