During a psychosis, individuals often describe mystic experiences (Nelson and Sass, 2008; Podvoll, 1990). The Oxford psychologist and philosopher William James (1902) commented on the similarities between mystic experiences and mental illness, which he calls lower mysticisms:
It is evident that from the point of view of their psychological mechanism, the classic mysticism and these lower mysticisms spring from the same mental level, from that great subliminal or transmarginal region of which science is beginning to admit the existence, but of which so little is really known. That region contains every kind of matter: ‘seraph and snake’ abide there side by side. To come from thence is no infallible credential. What comes must be sifted and tested, and run the gauntlet of confrontation with the total context of experience, just like what comes from the outer world of sense. Its value must be ascertained by empirical methods, so long as we are not mystics ourselves.