 The problem for Epicurus was to find a way of explaining the natural phenomena of bodily movement while responding to the challenges posed by Aristotle’s criticisms of Democritus’ theory. Epicurus rose to the challenge, although one cannot be certain that he was responding directly to Aristotle’s critique. (It is unclear whether or how much philosophers of Epicurus’ generation who were not members of Aristotle’s own school had access to Aristotle’s treatises.)