The concept of self-motion is not only fundamental to Aristotle's argument for the Prime Mover and to ancient and medieval theories of nature, but it is also central to many theories of human agency and moral responsibility. In this collection of essays, scholars of classical, Hellenistic, medieval and early modern philosophy and science explore the question of the existence of self-movers and their motivations. They trace the development of the concept of self-motion from its formulation in Aristotle's metaphysics, cosmology and philosophy of nature through two millennia of philosophical, religious and scientific thought.