hear of phantom coaches (sometimes seen,
but more frequently heard), of phantom dogs, cats, horses, cattle, deer,
and even of phantom houses.

Whatever may be the causes of these and other false perceptions,--most
curious when the impression is shared by several witnesses,--they may
best be considered under the head of hallucination (q.v.).
Hallucinations may be pathological, i.e. the result of morbid conditions
of brain or nerve, of disease, of fever, of insanity, of alcoholism, of
the abuse of drugs. Again, they may be the result of dissociation, or
may occur in the borderland of sleep or waking, and in this case they
partake of the hallucinatory nature of dreams (q.v.). Again,
hallucinations may, once or twice in a lifetime, come into the
experience of the sane, the healthy, and, as far as any tests can be
applied, of the wide-awake. In such instances the apparition (whether it
take the form of a visual phantasm, of a recognized voice, of a touch,
or what not) may be coincidental or non-coincidental. The phantasm is
called coincidental if it represents a known and distant person who is
later found to have been dying or in some other crisis at the moment of
the percipient's experience. When the false perception coincides with
nothing of the sort, it is styled non-coincidental. Coincidental
apparitions have been explained by the theory of telepathy (q.v.), one
mind or brain impressing another in some unknown way so as to beget an
hallucinatory apparition or phantasm. On the evidence, so far as it has
been collected and analysed, it seems that the mind which, on the
hypothesis, begets the hallucinations, usually does so without
_conscious_ effort (see SUBLIMINAL SELF). There are, however, a few
cases in which the experiment of begetting, in another, an hallucination
from a distance, is said to have been experimentally and consciously
made, with success.

If the telepathic theory of coincidental hallucinations be accepted, we
have still to account for the much more common non-coincidental
apparitions of the living who do not happen to be in any particular
crisis. In these instances it cannot be demonstrated that telepathy has
_not_ been at work, as when a person is seen at a place which he thought
of visiting, but did not visit. F.W. Myers even upheld a theory of
psychorhagy, holding that the spirits of some persons have a way of
manifesting themselves at a distance by a psychic invasion. This
involves, as he remarked,