Nowadays people who suffer from psychotic delusions are more likely to be medicated rather than institutionalized. Among other things, this reduces the chances that a mental patient who thinks he is Jesus Christ will encounter anyone else with similar inclinations. In 1959, when institutionalization was still the favored treatment, a Michigan State psychology professor named Milton Rokeach found three such individuals on the same ward of the Ypsilanti State Hospital. Dr. Rokeach conducted a series of experiments to see what would happen when these patients were forced to interact with others who claimed the same identity. He reasoned that even seriously deluded patients would recognize they couldn't all be Jesus Christ. However, if Dr. Rokeach had hoped to put a dent in their delusions, he was disappointed. Two of the three concluded they were the genuine article and the others were crazy. The third, who variously thought of himself as King Oedipus, Jesus and God, simply adopted yet another new identity.
Believing oneself to be God would seem to present incontrovertible evidence of a serious mental disorder. Yet the distinction between delusion and sanity in such circumstances is not always clear-cut. Egyptian pharaohs and Roman emperors were worshipped as gods and might be forgiven for believing their own hype. Cult leaders have made similar claims about themselves, whether because they are deranged or are merely power hungry. Then there are mystics who become so completely absorbed in God that their identity as separate beings is at best provisional. They have come to recognize a deeper truth: that the delusion is not necessarily in thinking they are God but in thinking they are not.
*Milton Rokeach, The Three Christs of Ypsilanti
Steven Marcus, "The Poetry of Madness," New York Review of Books, June 11, 1964