The author reviews the psychosexual phases of development, emphasizing how Freud modified his theoretical constructs in the wake of clinical experience. Particular attention is paid to instinctual drives on the psychic organizers for later structural development. The author stresses the drive of mastery, and the pleasure derived from muscular activity and play that gains prominence during the anal sadistic phase. She underscores the fact that insufficient weight is given to the sadistic component as a significant factor in psychosexual development during the anal phase. Academic psychologists fail to give sufficient recognition to the drive aspects of human behavior.