Aristotle’s criticism of Platonic Forms in the Metaphysics has been a major source for the understanding and developments of the theory of Forms in later Antiquity. One of the cases in point is Aristotle’s argument, in Metaphysics I 9, 990b22-991a2, against Forms of non-substances. In this paper, I will first provide a careful analysis of this passage. Next, I will discuss how the argument has been interpreted ‐ and refuted ‐ by the fifth-century Neoplatonists Syrianus and Proclus. This interpretation has played an important role in the broader context of the Neoplatonic debates on the range of Plato’s theory of Forms, which was one of the traditional problems discussed about the Forms in later Platonism.
This paper analyses the central function that the Forms of Likeness and Unlikeness perform in the metaphysics of Proclus. Mainly drawing from Proclus’ Commentary on the Parmenides, the focus will be on the double role of these Forms as causes of the (reciprocal) relations of (un)likeness between different sensible particulars on the one hand and of the (asymmetric) relations between sensible particulars and the Forms in which they partake on the other. It will be argued that the relations of (un)likeness between sensible particulars, while not identical to the corresponding relations between particulars and Forms, can nonetheless be related to the causal operation of the same Forms. One can therefore conclude that Proclus’ account of the causality of Likeness and Unlikeness – despite its complexity, which is partly due to the combination of exegetic and more systematic considerations – is consistent.