An enduring interest in categories (katēgoriai),1 and in Aristotle’s Categories in particular, has led readers since antiquity to study the treatise which Porphyry entitled On the Genera of Being (6.1–3).2 Ancient and modern readers broadly agree that: (1) Plotinus understands his own subject matter to be ‘the kinds of things that exist’ (peri tōn genōn tou ontos); (2) the treatise displays the result of a deep and substantial engagement with Aristotle’s Categories; and (3) Plotinus raises important and substantive puzzles (aporiai) about what is said in the Categories.3 Beyond this, plausible interpretations diverge. On one view, Plotinus deploys the resources of earlier Platonist critics to challenge the Categories’ ontological prioritization of particular substance, especially as it is treated by earlier Aristotelian commentators.4 On an alternative reading, Plotinus ‘purifies’ Aristotelian ontology in order to sketch a new taxonomy of the sensible world, complementing his own account of the intelligible world and clearing a trail for Porphyry’s integration of Aristotle into a new Platonist curriculum.5