This Handbook examines the contributions of philosophy to psychoanalysis and vice versa. It explores the most central concept of psychoanalysis—the unconscious—in relation to its defences, transference, conflict, free association, wish fulfilment, and symbolism. It also considers psychoanalysis in relation to its philosophical prehistory, the recognition and misrecognition afforded it within twentieth-century philosophy, its scientific strengths and weaknesses, its applications in aesthetics and politics, and its value and limitations with respect to ethics, religion, and social life. The book explains how psychoanalysis draws our attention to the reality of central aspects of the inner life and how philosophy assists psychoanalysis in knowing itself. This introduction elaborates on the phrase ‘know thyself’, the words inscribed at the Temple of Delphi, and illustrates the connection between matters philosophical and psychoanalytic in relation to the Delphic command by highlighting their mutual concern with truth and truthfulness.