Let us consider first how far this withdrawal of the living man's spirit from his organism has been rendered conceivable by evidence already obtained.
First of all, the splits, and substitutions of phases of personality with which our second chapter made us familiar have great significance for possession also.
We have there seen some secondary personality, beginning with slight and isolated sensory and motor manifestations, yet going on gradually to complete predominance,—complete control of all supraliminal manifestation.
The mere collection and description of such phenomena has up till now savoured of a certain boldness. The idea of tracing the possible mechanism involved in these transitions has scarcely arisen.
Yet it is manifest that there must be a complex set of laws concerned with such alternating use of brain-centres;—developments, one may suppose, of those unknown physical laws underlying ordinary memory, of which no one has formed as yet even a first rough conception.
An ordinary case of ecmnesia may present problems as insoluble in their way as those offered by spirit-possession itself. There may be in ecmnesia periods of life absolutely and permanently extruded from memory; and there may be also periods which are only temporarily thus extruded. Thus on Wednesday and Thursday I may be unaware of what I learnt and did on Monday and Tuesday; and then on Friday I may recover Monday's and Tuesday's knowledge, as well as retaining Wednesday's and Thursday's, so that my brain-cells have taken on, so to say, two separate lines of education since Sunday—that which began on Monday, and that which began on Wednesday. These intercurrent educations may have been naturally discordant, and may be fused in all kinds of ways in the ultimate synthesis.
These processes are completely obscure; and all that can be said is that their mechanism probably belongs to the same unknown series of operations which ultimately lead to that completest break in the history of the brain-cells which consists in their intercalary occupation by an external spirit.
Passing on to genius, which I discussed in my third chapter, it is noticeable that there also there is a certain degree of temporary substitution of one control for another over important brain-centres. We must here regard the subliminal self as an entity partially distinct from the supraliminal, and its occupation of these brain-centres habitually devoted to supraliminal work is a kind of possession, which illustrates in yet another way the rapid metastasis of psychical product (so to term it) of which these highest centres are capable. The highest genius would thus be the completest self-possession,—the occupation and dominance of the whole organism by those profoundest elements of the self which act from the fullest knowledge, and in the wisest way.
The next main subject which fell under our description was sleep. And this state—the normal state which most resembles trance—has long ago suggested the question which first hints at the possibility of ecstasy, namely, What becomes of the soul during sleep? I think that our evidence has shown that sometimes during apparent ordinary sleep the spirit may travel away from the body, and may bring back a memory, more or less confused, of what it has seen in this clairvoyant excursion. This may indeed happen for brief flashes during waking moments also. But ordinary sleep seems to help the process; and deeper states of sleep—spontaneous or induced—seem still further to facilitate it. In the coma preceding death, or during that "suspended animation" which is sometimes taken for death, this travelling faculty has seemed to reach its highest point.
I have spoken of deeper states of sleep, "spontaneous or induced," and here the reader will naturally recall much that has been said of ordinary somnambulism, much that has been said of hypnotic trance. Hypnotic trance has created for us, with perfect facility, situations externally indistinguishable from what I shall presently claim as true possession. A quasi-personality, arbitrarily created, may occupy the organism, responding to speech or sign in some characteristic fashion, although without producing any fresh verifiable facts as evidence to the alleged identity. Nay, sometimes, as in a few of the Pesaro experiments (see Proceedings S.P.R., vol. v. pp. 563-565), there may be indications that something of a new personality is there. And on the other hand, the sensitive's own spirit often claims to have been absent elsewhere,—much in the fashion in which it sometimes imagines itself to have been absent during ordinary sleep, but with greater persistence and lucidity.