The belief in hallucinations

is probably a sort of ideology. There may be no one who actually hallucinates. The idea of hallucinations probably began as a way of scapegoating an imaginary other when there was no physical person at hand to scapegoat: "The devil made me do it." When we were no longer able to believe in demons, we began to believe in "hallucinations." Artists of course saw the amazing creative potential in the idea of hallucinations, just as they had in ghosts and goblins, demons, etc. Someday we may realize that no one actually hallucinates and everyone is a liar and some other excuse will have to be found for why people kill and where beautiful imagery in stories comes form, what motivates the characters, etc.