The condition known as Multiple Personality Disorder (MPD) or Dissociative Identity Disorder (DID) is metaphysically strange. Can there really be several distinct persons operating in a single body? Our view is that DID sufferers are single persons with a severe mental disorder. In this paper we compare the phenomenology of dissociation between personality states in DID with certain delusional disorders.We argue both that the burden of proof must lie with those who defend the metaphysically extravagant Multiple Persons view and that there is little theoretical motivation to yield to that view in light of the fact that the core symptoms of DID bear remarkable similarity to the symptoms of these other disorders where no such extravagance is ever seriously entertained.