as
possible, there are no means of distinguishing facts obtained in this
way from facts obtained by independent clairvoyance. In practice no
evidence has been obtained pointing to the possession by a discarnate
spirit of knowledge not possessed by any living person (see MEDIUM). As
explanation of the few successful experiments in independent
clairvoyance we have the choice of three explanations: (1) lucidity; (2)
telepathy from living persons; (3) hyperaesthesia. The second
possibility was overlooked in Richet's diagram experiments; it cannot be
assumed that a picture put into an envelope and not consciously recalled
has been in reality forgotten. Similarly the clairvoyant diagnosis of
diseases may depend on knowledge gained telepathically from the patient,
who may be subliminally aware of diseased states of the body. The most
elaborate experiments are by Prof. Richet with a hypnotized subject who
succeeded in naming twelve cards out of sixty-eight. But no precautions
were taken against hyperaesthesia further than enclosing the card in a
second envelope. There is a power possessed by a certain number of
people, of naming a card drawn by them or held in the hand face
downwards, so that there is no normal knowledge of its suit and number.
Few thorough trials have been made; but it seems to point to some kind
of hyperaesthesia rather than to clairvoyance; in the Richet experiments
even if the envelopes excluded hyperaesthesia of touch on the part of
the medium, there may have been subliminal knowledge on Prof. Richet's
part of the card which he put in the envelope. The experience known as
the _deja vu_ has sometimes been explained as due to clairvoyance.

_Telepathic Clairvoyance._--For a discussion of this see TELEPATHY and
CRYSTAL-GAZING. It may be noted here that some curious relation seems to
exist between apparently telepathic acquisition of knowledge and the
arrival of a letter, newspaper, &c, from which the same knowledge could
be directly gained. We are confronted with a similar problem in
attempting an explanation of the power of mediums to state correctly
facts relating to objects placed in their hands. Of a somewhat different
character is retrocognition (_q.v._), where the knowledge in many cases,
if telepathic, must be derived from a discarnate mind.

Clairvoyance, as a term of spiritualism, with its correlative
_clairaudience_, is the name given to the power of seeing and hearing
discarnate spirits of dead r