This thesis explores Joyce's lifelong questioning of subjectivity and language in terms of his work's largely overlooked context of multiple personality psychology, and parapsychology. Turn-of-the-century multiple personality encompassed a diverse set of pre-Freudian psychologies and discourses - hypnosis, hysteria, spiritualism, psychical research, psychopathology, and Gothic literature—constellated around the period's discovery of the unconscious and its unsettling vision of a psychically porous and multiplex self. These models of the mind—and the fears and fantasies attached to them— provide a context not only for the social and psychic reality in Joyce's fiction but also for the various procedures associated with his modernist assault on character and narrative.