In Metaphysics Λ, Aristotle appeals to the prime mover: an unmoved mover that is the first moving cause of the world. Elsewhere, he calls the science concerned with the prime mover ‘theology’ (Meta. E.1, 1026a19). But what is the point of this science? On a common view, its purpose is to give an account of the prime mover itself, and especially to prove its existence. By contrast, I argue that Aristotle’s theology in Metaphysics Λ is ‘nature-bound’: it ultimately aims at (...) explaining facts about the perceptible world, in particular the motion of heavenly bodies and the cycle of generation of perishable substances. (shrink)