Plato’s dialogue Parmenides remains one of—if not, the—most perplexing text in the Platonic corpus. Specifically, it examines the difficulties surrounding the concepts of unity, multiplicity, and Being that are required for participation in the Ideas. One of the problems forced upon the young Socrates by Parmenides and Zeno in the second half of the dialogue concerns the relationship between Being (ὄν) and the One (ἕν), namely, how defensible is the oneness, or the unity, of the Idea if it also partakes (...) of Being? The text culminates in an aporia as to how to articulate the difference between the One (ἕν) and the many (πολλά), since if the one is, it becomes many. How do many beings share in the one mode of Being? Crucially, how are we to articulate the difference between the One and the many, or Being and beings? Where Plato’s answer invoking the enigmatic concept ‘exaiphnēs’ (ἐξαίφνης), the temporal becoming of the unity and plurality of the One, seems to contradict the privileging of presence that Heidegger charges him with, he nonetheless fails to offer an understanding of difference that has neither Being nor unity. I argue that Heidegger’s engagement with the problem of the ontological difference, and its development into the identification of Being with difference itself, offers solutions to this aporia in Plato’s Parmenides by addressing a difference that is irreducible to the one or the many, the relational or the derivative. This has significant consequences for understanding Heidegger’s critique of Plato as not just consisting of the privileging of presence but also the failure to respond to the problem of difference. (shrink)