 The idea that Parmenides’ arguments so problematized the phenomenon of change as to make developing an adequate theoretical account of it the central preoccupation of subsequent Presocratic natural philosophers is a commonplace of modern historical narratives. Unfortunately, this notion has no real ancient authority. Aristotle’s account at Physics 1.8.191a23–33 of the wrong turn he claims earlier natural philosophers took in trying to understand the principles of change has often been thought to legitimate this view, given the Eleatic-sounding argument it records. But Aristotle mentions Parmenides nowhere in the passage, and his complaint is in fact broadly directed against all the early Greek philosophers whose views he has been surveying previously in the book. He complains that they naively adopted the view that no fundamental entity or substance comes to be or perishes, the result being that they are unable to account for, because they disavow, substantial change, which is the very phenomenon Aristotle is most interested in explaining. Aristotle actually understands Parmenides’ thesis that what is is one (hen to on) and not subject to generation and change as belonging, not to natural philosophy, but to first philosophy or metaphysics (Cael. 3.1.298b14–24; cf. Metaph. 1.5.986b14–18, Ph. 1.2.184a25-b12).