The obvious conclusion was that telepathy must be a function not of a person's ordinary consciousness, but of what psychologists call the subconsciousness, thus accounting for the difficulty of invariably obtaining satisfactory results in telepathic experiments. In the light of these discoveries, then, the belief has been gaining ground that ghosts--real ghosts--are at most nothing but mental images impressed upon one mind by another through the subtle power of telepathy, and apprehended in the form of hallucinations of the various senses, just as any ordinary telepathic message may be apprehended. A person is stricken with a mortal illness, is fatally injured, or is passing through some other great crisis likely to terminate in death. Consciously or subconsciously, he thinks of loved ones far away, and is seized with a longing to get into touch with them once more, if only to notify them of the catastrophe threatening him. Across the intervening space, by what mechanism we as yet do not know, his thought wings its way to them, finds lodgment in their subconsciousness, and thence, when favoring conditions arise--as in some moment of mental relaxation--is projected into their consciousness before, at the time of, or after the sender's death, and is seen, or heard, it may be, as a Phantom Drummer, a Knocking Ghost, or the phantasmal image of the sender himself. If, however, conditions are such as to prevent the message from emerging from the recipient's subconsciousness into his field of conscious vision, it may, on occasion, as telepathic experiments have proved, be retransmitted to a third party, and by him be apprehended; as, for example, the Drummer of Cortachy, in the two instances cited above, was heard not by members of the Ogilvy family, but by comparative strangers. More than this, evidence has been accumulating to make it certain that in most cases not even telepathy is involved in the creation of ghosts, but that they are merely products of the seer's own subconsciousness. This was first clearly indicated by the results of an interesting "census of hallucinations," originated some years ago at the International Congress of Psychology, and simultaneously carried on--principally by members of the Society for Psychical Research--in the United States, England, France, Germany, and other countries. To thousands of persons the question was put: "Have you ever, when believing yourself to be completely awake, had a vivid impression of seeing or being touched by a living being or inanimate object, or of hearing a voice, which impression, so far as you could discover, was not due to any external physical cause?"