Simplicius' greatest contribution in his commentary on Aristotle on Physics 1.5-9 lies in his treatment of matter. This is its first translation into English. The sixth-century philosopher starts with a valuable elucidation of what Aristotle means by 'principle' and 'element' in Physics. Simplicius' own conception of matter is of a quantity that is utterly diffuse because of its extreme distance from its source, the Neoplatonic One, and he tries to find this conception both in Plato's account of space and in a stray remark of Aristotle's. Finally, Simplicius rejects the...