This comprehensive study of Marcuse's thought concentrates on his theory of freedom, arguing that it is this which supplies the key to all his writings. This argument is substantiated by a detailed chronological examination of Marcuse's works. The author shows the rigorous logic underlying Marcuse's thinking, which is often obscured in Marcuse's own presentation, and pays particular attention to the influence of Heidegger, and of Marx's notion of human labour. This sympathetic reconstruction of the subject attempts to rescue Marcuse from misunderstanding and superficial criticism, and argues that Marcuse's most famous work, One Dimensional Man, is in fact an aberration from the mainstream of his work. This book forms one of the most accessible and reliable treatments of Marcuse available.