The Parmenidean challenge

Nature, for Aristotle, is an inner principle of change. If we are fully to understand what it is for man to have a nature, we must understand Aristotle's conception of change. This is no trivial matter. For in the intellectual climate in which Aristotle grew up it was not obvious that change was possible at all. As Aristotle said,

The reference is obviously to the pre-Socratic Parmenides, and his followers, who argued that change was impossible. For a change to occur, Parmenides argued, something would have to come into existence from a state of non-existence. But from nothing nothing could come to be. But nor can something come to be from something, for something already exists and thus cannot come to be.