Thomas Aquinas and Jean-Paul Sartre are usually identified with completely different philosophical traditions: intellectualism and voluntarism. In this original study, Stephen Wang shows, instead, that there are some profound similarities in their understanding of freedom and human identity. Aquinas gives far more scope than is generally acknowledged to the open-endedness of reason in human deliberation, and argues that we can transform ourselves in quite radical ways through our choices. Sartre famously emphasizes the radical nature of choice, but also develops a subtle account of rationality and of the factual limits we encounter in the world and in ourselves. And in both thinkers the heart of human freedom lies in our ability to choose the goals we are seeking, as we search for an elusive fulfillment that lies beyond the confines of our temporal experience. This important study will interest Aquinas and Sartre scholars, as well as general readers seeking an introduction to their thought. It will also be invaluable for philosophers seeking fresh perspectives on questions of freedom, happiness, personal identity, act theory, meta-ethics, and theories of the self.