On Aristotle's Physics 3

the long version

Book 3 of Aristotle's Physics elaborates definitions of change and infinity - concepts central to his theory of nature. In a sixth-century commentary on Physics 3, Philoponus makes use of Aristotle's views to argue for a Christian interpretation of infinity. In Physics Book 2, Aristotle defines nature as an internal source of change. By elaborating Aristotle's view of change, Book 3 takes an important step in establishing the claim - to be made in Book 8 - for a divine mover who causes change but in whom no change occurs. Book 3 also introduces Aristotle's doctrine of infinity as always potential, but never actual and never traversed. Here, as elsewhere, Philoponus turns Aristotle's arguments about infinity against the pagan Neoplatonist belief in a universe without a beginning.