 Here is an overview of what follows. In Section 1, we acquaint the reader with some central historical contributions to our understanding of free will. (As nearly every major and minor figure had something to say about it, we cannot begin to cover them all.) As with contributions to many other foundational topics, these ideas are not of ‘merely historical interest’: present-day philosophers continue to find themselves drawn back to certain thinkers as they freshly engage their contemporaries. In Section 2, we map the complex architecture of the contemporary discussion of the nature of free will by dividing it into five subtopics: its relation to moral responsibility; the proper analysis of the freedom to do otherwise; a powerful, recent argument that the freedom to do otherwise (at least in one important sense) is not necessary for moral responsibility; ‘compatibilist’ accounts of sourcehood or self-determination; and ‘incompatibilist’ or ‘libertarian’ accounts of source and self-determination. In Section 3, we consider arguments from experience, a priori reflection, and various scientific findings and theories for and against the thesis that human beings have free will, along with the related question of whether it is reasonable to believe that we have it. Finally, in Section 4, we survey the long-debated questions involving free will that arise in classical theistic metaphysics.