One of the most influential of contemporary philosophers, Harry Frankfurt has made major contributions to the philosophy of action, moral psychology, and the study of Descartes. This collection of essays complements an earlier, successful collection published by Cambridge, The Importance of What We Care About. These essays deal in general with foundational metaphysical and epistemological issues concerning Descartes, moral philosophy, philosophical anthropology, political philosophy, and religion. A hallmark of Frankfurt's work is his crisp and incisive style, which means that these essays should appeal to a wide range of philosophers and to readers in neighboring disciplines with philosophical interests.