Visions: The appearance to mortals of supernatural persons, or scenes…. In medieval
Europe, visions were almost
commonplaces, and directions were given by the Church to enable men to distinguish visions of divine origin from
those
false delusions which were the work of the Evil One…. Ennemoser enumerates the causes of such appearances thus:
(1)
Sensitive organism and delicate constitution; (2) Religious education and ascetic life; (3) Narcotics —
opium,
wine,
incense, narcotic salves; (4) Delirium, monomania; (5) Fear and expectation, preparatory words, songs, and
prayers.
— Lewis Spence, An Encyclopaedia of Occultism: A Compendium of
Information on the Occult Sciences, Occult Personalities, Psychic Science, Magic, Demonology, Spiritism,
Mysticism and Metaphysics (George Routledge & Sons, 1920)