Abstract

There are people where two or more personalities seem to have independent-and sometimes mutually forgetful-control of the same bodily individual. This chapter gives a brief account of the history of the diagnosis of "Multiple Personality Disorder" or "Dissociative Identity Disorder", and the conflicting judgment of therapists, lawyers, and philosophers as to whether this is a real syndrome. It is suggested that the diagnosis may be therapeutically helpful for some other disturbances, including anorexia, even if it does not carry the strong metaphysical moral that some have supposed. The cases are of interest to philosophers as they purport to represent "real -life" difficulties for standard theories of "personal identity." The chapter argues that the diagnosis depend on prior assumptions about such identity, and so don't easily confirm or rebut any available theory, including more ancient theories about demonic possession.