§ 1. The telepathic cases quoted in the foregoing chapters have almost all affected a single percipient only; and the fact that sometimes the percipient was in company at the time, and that his sensory experience was unshared by any one present, has confirmed the view (to which all other considerations seemed to converge) that telepathic affections of the senses are in the most literal sense hallucinations. But we have already encountered a few cases where the senses of more than one percipient have been affected;1 and what awaits us in the present chapter is the discussion and complete illustration of this perplexing feature.

Of course the first view which is suggested by the fact that two or more people have seen or heard the same thing at the same time is that the sight or sound, however abnormal and unaccountable, was due to some objective reality within the range of their sense-organs - in other words, that it was not a hallucination at all.2 Hence those apparently telepathic instances where a sensory experience, representative of some absent person, has been shared by more than one percipient, would imply the immediate presence of some sort of physical wraith, or at any rate of an objective human presence.

I scarcely know how far the idea of a literal wraith is seriously entertained by any educated person in the present day. Gaseous and vaporous ghosts are, I imagine, quite at a discount; but the word "ether" seems sometimes to be used as a way out of the difficulty. For many ears the word has, no doubt, a convenient vagueness; but, in fact, we know of no mode by which ether can affect the retina, except through waves started by luminous substances of known type. And even if etherial ghosts could be seen, the auditory phenomena would remain a hopeless obstacle to a satisfactory physical explanation of them. For even the assumption of some tenuous and elusive form of matter, which somehow hangs about in relation to the mysterious ether, seems less desperate than the assumption that such a tenuous presence could move the air in the infinitely complex vibration-patterns which correspond to speech or music - that is to say, could produce at will an effect of inconceivable difficulty and complexity on certain gross elements of the known material world.

As to the notion of an objective presence which may affect the perceptive faculty of several persons without producing changes in the external world, one sort of case is conceivable which would no doubt favour it - e.g., if two persons, situated at some distance from one another, saw the appearance in the respective relations of distance and posture which a real object of the same kind would bear to them - one of them, it might be, seeing a full face, and the other a profile. But I know of no examples of this sort. And as a mere theory, the notion in question may be left with a single general comment; for though our path skirts, it had better not enter, the metaphysical labyrinth suggested by the words "objective reality." Let it be conceded then that, where there is a consensus of perception, it becomes a nice question for Idealism to determine how far, or in what sense, the percept lacks an objective basis. To put an extreme case - suppose all the seeing world, save one individual, had a visual percept, the object of which nevertheless eluded all physical tests: would the solitary individual be justified in saying that all the others were victims of a subjective delusion? and if he said so, would they agree with him? But then in this case, or in a less extreme one of the same kind, we might at any rate ask one of the perceivers to tell us what meaning he can attach to the objectivity of his percept, beyond that it has its existence in other minds besides his own.

If he fails to supply us with any further meaning, on him surely lies the onus of proving that the conditions of the percept lie outside the perceiving minds; and if no proof be forthcoming, I see no definite way of distinguishing this "objective" view of " collective hallucinations "from the view to be considered immediately, which regards the community of percipience as a form of thought-transference.1

1 Nos. 14, 36, 254 (first incident), 308. See also the dream-case 127.

2 It was in this occasional feature of collective percipience that Falck, in 1692, found the strongest argument for the production of hallucinations by an external and daemonic power. See p. 72 of his able and elaborate dissertation against Hobbes and Spinoza, in De Demonologia recentiorum Autorum.

"But" - some objectors may say - " the question has been begged by assuming that the collective percept eludes physical tests. True, apparitions have not yet been subjected to spectroscopic analysis, nor have phantasmal remarks been recorded by the phonograph; but suppose that the form of a dying person not only appears, but opens the door or the window, and the door or the window remains open, thus affording to the muscles of the servant who closes it a test of a physical change in the external world - what account is to be given of this? " Now clearly such phenomena, even if established, would afford no convincing analogy by which to judge of cases where no similar physical tests are included. But, as a matter of fact, no records of the sort that we have met with have reached the evidential standard which would entitle them to a place in this book (see pp. 125-6); and until they are extablished by irrefragable evidence, there is another analogy which has in every way a prior claim - namely, the facts of telepathy as so far set forth.

Cannot our further facts be explained without going beyond the purely psychical transference for which we believe that we have ample evidence?

Let us see in what ways a theory of purely psychical impressions could cover the phenomena of collective hallucinations. Two possible views of what may happen present themselves. The first of these would apply only to veridical cases - cases which are "telepathic" in the literal sense. On this view the simultaneous experiences would be traced to a cause external to the percipients; but this cause would not be a real object within the range of the percipient's senses, but a real condition of an absent person. A, who is passing through some crisis at a distance, produces a simultaneous telepathic impression on the minds of B and of C, who happen to be together; both B and C project this impression as a hallucination of the senses, in the way that has been so fully considered; and the hallucinations more or less nearly resemble each other.

1 A psychical condition outside the perceiving minds might, no doubt, be found in "disembodied intelligence." For the present, it is enough to remark that this change of "agency" to some further mind would leave the nature of the phenomenon unchanged. Experience thus caused may be called objective, if we will, but it is still thought-transference; just as in Berkeley's view the whole objective universe was only thought-transference in excels.

The second view would apply equally to the cases which are, and to those which are not, telepathic, in this literal sense of relating to a distant agent. The view is that the hallucination of one percipient, however caused, begets that of the other, by a process of thought-transference; the hallucination is in itself, so to speak, infectious. B and C are together, and B has a hallucination - it may be veridical and due to a telepathic impression from the distant A, or it may be non-veridical and due to a spontaneous pathological disturbance of B's own brain; and this experience of B's is then communicated to C, whose brain follows suit and projects a kindred image. The process in fact would strongly recall those cases of simultaneous dreaming where one dream may be regarded as the cause of the other (see pp. 217-9). It would be a fresh example of the psychological identity between the sleeping and the waking hallucinations on which so much stress has already been laid.

Such are the two possible views; and we have now to decide how far either, or both, may be reasonably entertained. I may state at once that in my opinion the best solution that the problem at present admits of involves a certain combination of the two (see § 7 below); but I shall consult clearness by first considering each of them separately.