 The term “free will” has emerged over the past two millennia as the canonical designator for a significant kind of control over one’s actions. Questions concerning the nature and existence of this kind of control (e.g., does it require and do we have the freedom to do otherwise or the power of self-determination?), and what its true significance is (is it necessary for moral responsibility or human dignity?) have been taken up in every period of Western philosophy and by many of the most important philosophical figures, such as Plato, Aristotle, Augustine, Aquinas, Descartes, and Kant. (We cannot undertake here a review of related discussions in other philosophical traditions. For a start, the reader may consult Marchal and Wenzel 2017 and Chakrabarti 2017 for overviews of thought on free will, broadly construed, in Chinese and Indian philosophical traditions, respectively.) In this way, it should be clear that disputes about free will ineluctably involve disputes about metaphysics and ethics. In ferreting out the kind of control at stake in free will, we are forced to consider questions about (among others) causation, laws of nature, time, substance, ontological reduction vs emergence, the relationship of causal and reasons-based explanations, the nature of motivation and more generally of human persons. In assessing the significance of free will, we are forced to consider questions about (among others) rightness and wrongness, good and evil, virtue and vice, blame and praise, reward and punishment, and desert. The topic of free will also gives rise to purely empirical questions that are beginning to be explored in the human sciences: do we have it, and to what degree?