Robert Kane provides a critical overview of debates about free will of the past half century, relating this recent inquiry to the broader history of the free will issue and to vital currents of twentieth century thought. Kane also defends a traditional libertarian or incompatibilist view of free will (one that insists upon the incompatibility of free will and determinism), employing arguments that are both new to philosophy and that respond to contemporary developments in physics and biology, neuro science, and the cognitive and behavioral sciences.