Both Plotinus and Porphyry contribute in their own ways to the tradition of neoplatonic commentaries on Aristotle’s Categories. In 6.1-2, Plotinus argues that Aristotle’s ten categories are not adequate as an account of the genera of Being and that for this purpose they ought to be supplanted by the five greatest kinds from Plato’s Sophist. In 6.3, he acknowledges that it would be desirable to have a system of categories, not genera, for the sensible realm. He proposes several reductions of Aristotle’s ten categories to more compact schemes and finally seems to settle on the number five: composite, relative, quantity, quality and motion. The extent to which Porphyry was at odds with Plotinus over the value of Aristotle’s Categories is the subject of debate. Porphyry is certainly keen to claim that the work is about ‘simple significant words insofar as they signify things’ (in Cat. 58,5) and defends it against critics who claim that Aristotle has got the number of divisions wrong (in Cat. 59,10-34). In what follows I argue that Porphyry has managed to get clear about relations and relational properties in a way that Plotinus has not. As a result, the latter is not well placed to meet potential objections to the autonomy of Aristotle’s category of relatives. Since this is a category that Plotinus seems to retain in his own five-fold system, this is a problem for him.
Baltzly, Dirk, "Porphyry and Plotinus on the Reality of Relations" (1997). The Society for Ancient Greek Philosophy Newsletter. 310.