Porphyry's List of Questions

In Aristotelian logic, the kind of universals Porphyry was interested in were the species and genera of substances. Boethius assumed that for Porphyry, universals are indeed both real and incorporeal. Groucho, Chico, Harpo, and Zepo are all similar in being humans, but it is only at the level of mental understanding that we isolate humanity as its own right.