I once had a friend who was a renowned clinical psycologist. He used to tell me about all the patients he had seen.
One of the most interesting cases he told me about involved a schizophrenic with multiple personality disorder.
At times this person believed himself to be a temptress in a Bizet opera.
At other times he was convinced that he was the head of the German Luftwaffe in WW II.
The concensus of the practitioners was that the poor fellow didn't know if he was Carmen or Goerring...