Book excerpt: Harry Stack Sullivan (1892-1949) has been described as 'the most original figure in American psychiatry'. Challenging Freud's psychosexual theory, Sullivan founded the interpersonal theory of psychiatry, which emphasized the role of interpersonal relations, society and culture as the primary determinants of personality development and psychopathology. This concise and coherent account of Sullivan's work and life invites the modern audience to rediscover the provocative, groundbreaking ideas embodied in Sullivan's interpersonal theory and psychotherapy.