This book investigates what was distinctive about the predisposition to psychosis Freud posited in Daniel Paul Schreber, a presiding judge in Saxony’s highest court. It argues that Freud’s 1911 Schreber text reversed the order of priority in late nineteenth-century conceptions of the disposing causes of psychosis - the objective-biological and subjective-biographical - to privilege subjective disposition to psychosis, but without returning to the paradigms of early nineteenth-century Romantic psychiatry and without obviating the legitimate claims of biological psychiatry in relation to hereditary disposition. While Schreber is the book’s reference point, this is not a general treatment of Schreber, or of Freud’s reading of the Schreber case. It focuses rather on what was new in Freud’s thinking on the disposition to psychosis, what he learned from his psychiatrist contemporaries and what he did not, and whether or not psychoanalysts have fully received his aetiology.