Unconscious Thought in Philosophy and Psychoanalysis explores concepts throughout the history of philosophy that suggest the possibility of unconscious thought and lay the foundation for ideas of unconscious thought in modern philosophy and psychoanalysis. The book considers the workings of unconscious thought, and the role that unconscious thought plays in thinking, language, perception, and human identity. The focus is on the metaphysical and philosophical concepts of unconscious thought, as opposed to the empirical or scientific phenomenon of 'the unconscious', and it is argued that these metaphysical concepts still played an important role in the psychoanalysis of Sigmund Freud and Jacques Lacan. With chapters drawing on a wide range of philosophers from Plotinus to Freud and Lacan, Unconscious Thought in Philosophy and Psychoanalysis casts an original and thought-provoking perspective on the relation between unconscious thought and conscious thought, different kinds of thinking, and the relation between thinking and perceiving.