One of Freud's central achievements was to demonstrate how unacceptable thoughts and feelings are repressed into the unconscious, from where they continue to exert a decisive influence over our lives. This volume contains a key statement about evidence for the unconscious, and how it works, as well as major essays on all the fundamentals of mental functioning. Freud explores how we are torn between the pleasure principle and the reality principle, how we often find ways both to express and to deny what we most fear, and why certain men need fetishes for their sexual satisfaction. His study of our most basic drives, and how they are transformed, brilliantly illuminates the nature of sadism, masochism, exhibitionism and voyeurism.