Documentation of implicit expressions of memory in head-injured, mentally ill and normal individuals has offered a new perspective on the problem of unconscious influence on conscious experience, thought and action. The phenomenon of implicit memory is described and used as a basis to develop an analogous concept of implicit perception. In both cases the person shows the effects of current or past events, even though these events are not accessible to phenomenal awareness. There is collateral evidence for the emotional unconscious: emotional states can serve as evidence of implicit perception or memory, and there is evidence of desynchrony between the subjective experience of emotion, which can be identified with consciousness, and the effects of emotional responses on physiology and overt behaviour. Theoretical approaches to the psychological unconscious include a connectionist approach, which affords a limited role for conscious processing in mental life; a neuropsychological approach, involving the disconnection of a module serving consciousness from the rest of the cognitive system; and a psychological approach, which emphasizes the central role in conscious awareness of mental representations of the self as the agent or experiencer of events.