The problem of freedom and determinism is one of the most enduring, and one of the best, problems in philosophy. One of the best because it so tenaciously resists solution while yet always seeming urgent, and one of the most enduring because it has always been able to present itself in different ways to suit the preoccupations of different ages. This book, first published in 1980, sets out to defend free will: it elaborates a sober and systematic case for libertarianism in the face of the overwhelming threat that is posed by the scientific study of the brain.