First, then, as regards the vibratory hypothesis; it would demand a variety of media to convey separately something corresponding to the sense of sight, the sense of hearing, and to each of the other senses--touch, taste, and smell--as all these sensations have been telepathically transmitted, or else there must exist one single medium capable of transmitting these many widely different methods of sensation separately,--either of which suppositions are, to say the least, bewildering. Such a medium must also possess a power of penetrating or acting through intervening obstacles, such as no medium with which we are acquainted possesses; and, lastly, in addition to numerous apparently insurmountable difficulties and insufficiencies, there is no proof whatever that any such vibratory medium exists. Second. Regarding a vital effluence or some physical emanation or aura belonging to each individual, and by means of which communication is possible between persons separated by too great a distance to permit communication through the ordinary channels; it is at least conceivable that such an aura or personal atmosphere exists, and by some it is claimed to be demonstrated; but admitting its existence, that it would be capable of fulfilling the numerous functions demanded of it in the premises is doubtful. Third. That the telepathic intercommunication is accomplished by means of a sixth sense--a sort of compend of all the other senses, with added powers as regards distance and intervening obstacles--is a hypothesis which has been urged by some, and is at least intelligible; but, while it presents an intelligible explanation of such facts as clairvoyance and the hearing of voices, there is a large class of facts, as we shall see, which utterly refuse to fall into line or be explained by this hypothesis. Fourth. The hypothesis of different strata of personality--or of a second or subliminal self--is the one which best fulfils the necessary conditions and also harmonizes the greatest number of facts when arranged with reference to this idea. There is also real, substantial evidence that such a second personality actually exists, some of the facts bearing upon this subject having been presented in former chapters.