The distinction between Middle Platonism and Neoplatonism is controversial, but it remains helpful in that it makes it clear that there are important differences in the philosophical background of Platonist philosophers before and after Plotinus.1 One of these differences resides in their knowledge of Aristotle’s treatises. It can plausibly be argued that Platonist philosophers, from at least Eudorus of Alexandria onward (first century bc), regarded Aristotle as an authority, though not unqualifiedly so, and though his status was clearly inferior to that of Plato.2 Eudorus of Alexandria was certainly involved in the early debates on Aristotle’s Categories, and we know from Alexander of Aphrodisias (in Metaph. 58.25–59.8) that Eudorus proposed an emendation to Aristotle’s report on Plato’s theory of principles at Metaph.