If the temporal coincidence of the crisis and the distant apparitional experience cannot be explained by any conventional means, then in parapsychology the presumption is made that some as yet unknown form of communication, such as telepathy (a term coined by Myers[4]) has taken place.
He accepted the hallucinatory character of the experience, pointing out that it is virtually unknown for firsthand accounts to claim that apparitional figures leave any of the normal physical effects, such as footprints in snow, that one would expect of a real person.
These are some of the more notable differences, at least as indicated by their own collection of 1800 firsthand accounts: Apparitional experiences have relevance to psychological theories of perception, and in particular to the distinction between top-down and bottom-up approaches (cf.
Top-down theories, such as that of Richard Langton Gregory, who conceives of perception as a process whereby the brain makes a series of hypotheses about the external world,[13] stress the importance of central factors such as memory and expectation in determining the phenomenological content of perception; while the bottom-up approach, exemplified by the work of James J. Gibson, emphasises the role of the external sensory stimulus.
If, on the contrary, a dimensional view of the matter is taken, it becomes easier to conceive of how normal people, more or less high on the putative schizotypy dimension, might be more or less prone to anomalous perceptual experiences, without their ever tipping over into psychosis.
[18] Green and McCreery's identification of a class of what they called 'reassuring apparitions'[9] is of particular interest in this regard, as it suggests that the experiencing of hallucinations may even have an adaptive effect in certain subjects, making them better able to cope with adverse life events.
This would fit with the model of schizotypy as essentially a normal dimension of personality, and might help to explain why the proneness to anomalous perceptual experiences has apparently not been 'weeded out' by the process of natural selection.
The occurrence of hallucinations, that is, perceptual experiences 'having the character of sense perception, but without relevant or adequate sensory stimulation [...]',[19] have long been one of the standard objections to the philosophical theory of direct realism.