This book sets out to clarify five key Freudian concepts (the pleasure principle, the primary processes, the unconscious, transference, and the reality principle) elaborated early on in Freud's work but, it is argued, rarely understood—even by psychoanalysts themselves. It examines in turn the post-Freudian paradigms employed in neuropsychoanalysis, Lacan, Zizek, object relations, and psychoanalytic approaches to identity politics, and in doing so reveals the extent to which they have been distorted and repressed in these new contexts. Over the course of the book the author demonstrates how Freud's unpublished Project for a Scientific Psychology can be seen as a complete system of core concepts that both ground psychoanalysis in neurology and also introduce a vital challenge to the brain sciences. This book will appeal to students and scholars of psychoanalysis, clinical psychology, and psychoanalytic theory.