Abstract

In Metaphysics Λ.6-7 Aristotle argues that an unmoved substance causes the outermost sphere to rotate. His argument has puzzled and divided commentators from ancient Greece to the present. I offer a novel defense of Aristotle's argument by highlighting the logic of classification that Aristotle deploys. The core of Aristotle's argument is the identification of the unmoved substance on the 'table of opposites' as simple and purely actual. With this identification in place, Aristotle argues that the outermost sphere activates its capacity to relocate its body by rotating because this is how it can be a simple and actual substance. But unlike traditional attempts to rehabilitate Aristotle's argument, I argue that the sphere does not rotate in order to imitate the Prime Mover. Rather, the sphere rotates because that is good for it to do, and the Prime Mover is a metaphysically necessary source of simple and actual substantial being, which the sphere acts for the sake of.