In the first place, let us try to realize theoretically what is involved in the supposition that any sort of invisible intelligence can become in any way known to us. I speak of the methods of communication only, without reference to the nature of the supposed intelligence, beyond the mere fact of its habitual invisibility. It is plain, I think, that the said intelligence must either so act upon visible matter as to affect our sense-organs in the ordinary way, or else must convey messages to our minds by some director process, not depending on the intervention of our organs of sense. Now probably no one will assume that the first method will alone be employed. Even those who insist, with Mr. Wallace, on the objectivity of apparitions, do not, I think, maintain that it is _only_ by moving material objects that unseen intelligences affect our minds. Few will doubt that _if_ there be communication from unseen beings at all, it will probably be at least partly in the second of the two modes already specified, that is, that it will reach our minds in some way more intimate and direct than by ordinary sense-perception. But if this be so, then there must be in our minds a certain power of reciprocity. We must be able to receive the message in the same impalpable way in which the unseen intelligence communicates it. But if we suppose that man possesses this power of receiving direct or telepathic messages from unembodied or invisible intelligences, it is natural to inquire whether he is capable of receiving similar messages from embodied or visible intelligences. If we cannot find that he is thus capable, our belief in the supposed messages from the unseen will be doubly difficult; for we shall have to postulate both the new forms of intelligence and the new mode of intercourse. But if, on the other hand, we can show that the mode of intercourse here needed does already exist, and appears in man's relations with his fellow-men, then the transition to messages from the unseen will be so much the less violent. We shall only be supposing that man can receive from the disembodied a kind of message which he already receives from the embodied, and which has no obvious dependence on a corporeal embodiment. One single proved transmission, direct from mind to mind, of the most trivial fact or percept, will do more to make communion with the unseen _scientifically_ conceivable,--I do not say more to make it _morally_ conceivable,--than all the poetry and all the rhetoric which has ever stirred the hearts of men. Such, on the one side, is my deductive argument from the very conception of communication with unseen intelligences.