No serious attempts to investigate the conditions or results of thought-transference appear to have been undertaken before the middle of last century. It was not indeed until 1876 that Sir William Barrett really initiated the careful and scientific study of telepathic phenomena which has been continued by the Society for Psychical Research in England and on the Continent by Boirac, Osty, Tischner, and many other distinguished savants. The results obtained have been, it is true, questioned and criticized at every turn by certain scientists who deny that telepathy is either proven or indeed possible. Professor Jodl (quoted by Tischner) goes so far as to say: “Such a direct transmission of ideas from one mind to another, without any perceptible physical method of communication, would indicate the presence of a crack in the very foundations of all our views on Nature.” “Psycho-physics”, writes Dr Henning, “yes, even psychology as a science must be utterly wrecked before we have recourse to telepathy.” It is, however, useless to indulge in mere _a priori_ refutations or, in the case of telepathic experiments, to concentrate on the failures and ignore the successes. It is of course impossible within the very narrow space-limits of this little book to furnish any detailed reference of such experiments. Suffice it to say that evidence varied, cumulative and irresistible now exists which has established telepathy as a scientific fact. The study of telepathic phenomena suggests the interesting question whether telepathy is a psychic factor of permanent and regular character or whether it represents merely the dying embers of a once more active force. Can the transference of human thought apart from physical media be developed and systematized on such a scale as to suggest immense possibilities in the human relationships of the future? Or will such development be inevitably retarded by the fact that telepathy is a dying sense to be classed with various obscure eccentricities of the human body which serve merely as vestigial landmarks in the long history of the race? Despite the alluring possibilities of the first suggestion, indications certainly exist which lend colour to the pathetic belief that research has only discovered this force in the evening of its existence. This view of telepathy as a “rudimentary survival” seems to be strengthened by the admitted fact that manifestations of telepathy are far more certain and more striking when the percipient is under hypnotic suggestion; for, if it be the subliminal self which rises above the threshold in hypnotic slumber and obeys the suggestion of the agent’s mind, this is itself in all probability a manifestation of race-experience rather than that of the individual. The everyday self, the product of normal experience, is influenced to a much slighter degree by hypnotic suggestion than that mysterious entity, the secondary self, trailing its clouds of precarnate existence.