 As a thoroughgoing materialist,  Epicurus[12]  (341–271 BCE) could not accept the notion of potentiality on which Aristotle’s theory of continuity rested, and so was propelled towards atomism in both its conceptual and physical senses. Like Leucippus and Democritus, Epicurus felt it necessary to postulate the existence of physical atoms, but to avoid Aristotle’s strictures he proposed that these should not be themselves conceptually indivisible, but should contain conceptually indivisible parts. Aristotle had shown that a continuous magnitude could not be composed of points, that is, indivisible units lacking extension, but he had not shown that an indivisible unit must necessarily lack extension. Epicurus met Aristotle’s argument that a continuum could not be composed of such indivisibles by taking indivisibles to be partless units of magnitude possessing extension.