The results of these inquiries show that a great number of sensory automatisms occur among sane and healthy persons, and that for many of these we can at present offer no explanation whatever. For some of them, however, we can offer a kind of explanation, or at least an indication of a probable determining cause, whose mode of working remains wholly obscure.
Thus, in some few instances, although there is no disturbance of health, there seems to be a predisposition to the externalisation of figures or sounds. Since this in no way interferes with comfort, we must simply class it as an idiosyncratic central hyperæsthesia—much like the tendency to extremely vivid dreams, which by no means always implies a poor quality of sleep.
In a few instances, again, we can trace moral predisposing causes—expectation, grief, anxiety.
These causes, however, turn out to be much less often effective than might have been expected from the popular readiness to invoke them. In two ways especially the weakness of this predisposing cause is impressed upon us. In the first place, the bulk of our percipients experience their hallucinations at ordinary unexciting moments; traversing their more anxious crises without any such phenomenon. In the second place, those of our percipients whose hallucination is in fact more or less coincident with some distressing external event, seldom seem to have been predisposed to the hallucination by a knowledge of the event. For the event was generally unknown to them when the corresponding hallucination occurred.
This last remark, it will be seen, introduces us to the most interesting and important group of percipients and of percepts; the percipients whose gift constitutes a fresh faculty rather than a degeneration; the percepts which are veridical—which are (as we shall see cause to infer) in some way generated by some event outside the percipient's mind, so that their correspondence with that event conveys some new fact, in however obscure a form. It is this group, of course, which gives high importance to the whole inquiry; which makes the study of inward vision no mere curiosity, but rather the opening of an inlet into forms of knowledge to which we can assign no bound.
Now these telepathic hallucinations will introduce us to very varying forms of inward vision. It will be well to begin their study by recalling and somewhat expanding the thesis already advanced: that man's ocular vision is but a special or privileged case of visual power, of which power his inner vision affords a more extensive example.
Ocular vision is the perception of material objects, in accordance with optical laws, from a definite point in space. Our review of hallucinations has already removed two of these limitations. If I see a hallucinatory figure—and figures seen in dreams come under this category—I see something which is not a material object, and I see it in a manner not determined by optical laws. A dream-figure may indeed seem to conform to optical laws; but that will be the result of self-suggestion, or of organised memories, and will vary according to the dreamer's visualising power. While a portrait-painter may see a face in dream which he can paint from memory when he wakes, the ordinary man's dream-percept will be vague, shifting, and unrememberable.
Similarly, if I see a subjective hallucinatory figure "out in the room," its aspect is not determined by optical laws (it may even seem to stand behind the observer, or otherwise outside his visual field), but it will more or less conform—by my mere self-suggestion, if by nothing else—to optical laws; and, moreover, it will still seem to be seen from a fixed point in space, namely, from the stationary observer's eyes or brain.
All this seems fairly plain, so long as we are admittedly dealing with hallucinatory figures whose origin must be in the percipient's own mind. But so soon as we come to quasi-percepts which we believe to exist or to originate somewhere outside the percipient's mind, our difficulties come thick and fast.
If there be some external origin for our inward vision (which thereby becomes veridical) we must not any longer assume that all veridical inward vision starts or is exercised from the same point. If it gets hold of facts (veridical impressions or pictures, not mere subjective fancies), we cannot be sure a priori whether it somehow goes to find the facts, or the facts come to find it. Again, we cannot any longer take for granted that it will be cognisant only of phantasmal or immaterial percepts. If it can get at phantasmal percepts outside the organism, may it not get at material percepts also? May it not see distant houses, as well as the images of distant souls?