The claim, then, is that the automatist, in the first place, falls into a trance, during which his spirit partially "quits his body:" enters at any rate into a state in which the spiritual world is more or less open to its perception; and in which also—and this is the novelty—it so far ceases to occupy the organism as to leave room for an invading spirit to use it in somewhat the same fashion as its owner is accustomed to use it.

The brain being thus left temporarily and partially uncontrolled, a disembodied spirit sometimes, but not always, succeeds in occupying it; and occupies it with varying degrees of control. In some cases (Mrs. Piper) two or more spirits may simultaneously control different portions of the same organism.

The controlling spirit proves his identity mainly by reproducing, in speech or writing, facts which belong to his memory and not to the automatist's memory. He may also give evidence of supernormal perception of other kinds.

His manifestations may differ very considerably from the automatist's normal personality. Yet in one sense it is a process of selection rather than of addition; the spirit selects what parts of the brain-machinery he will use, but he cannot get out of that machinery more than it is constructed to perform. The spirit can indeed produce facts and names unknown to the automatist; but they must be, as a rule, such facts and names as the automatist could easily have repeated, had they been known to him:—not, for instance, mathematical formulæ or Chinese sentences, if the automatist is ignorant of mathematics or of Chinese.

After a time the control gives way, and the automatist's spirit returns. The automatist, awaking, may or may not remember his experiences in the spiritual world during the trance. In some cases (Swedenborg) there is this memory of the spiritual world, but no possession of the organism by an external spirit. In others (Cahagnet's subject) there is utterance during the trance as to what is being discerned by the automatist, yet no memory thereof on waking. In others (Mrs. Piper) there is neither utterance as a rule, or at least no prolonged utterance, by the automatist's own spirit, nor subsequent memory; but there is writing or utterance during the trance by controlling spirits.

Now this seems a strange doctrine to have reached after so much disputation. For it simply brings us back to the creeds of the Stone Age. We have come round again to the primitive practices of the shaman and the medicine-man;—to a doctrine of spiritual intercourse which was once œcumenical, but has now taken refuge in African swamps and Siberian tundras and the snow-clad wastes of the Red Indian and the Esquimaux. If, as is sometimes advised, we judge of the worth of ideas by tracing their origins, no conception could start from a lower level of humanity. It might be put out of court at once as unworthy of civilised men.

Fortunately, however, our previous discussions have supplied us with a somewhat more searching criterion. Instead of asking in what age a doctrine originated—with the implied assumption that the more recent it is, the better—we can now ask how far it is in accord or in discord with a great mass of actual recent evidence which comes into contact, in one way or another, with nearly every belief as to an unseen world which has been held at least by western men. Submitted to this test, the theory of possession gives a remarkable result. It cannot be said to be inconsistent with any of our proved facts. We know absolutely nothing which negatives its possibility.

Nay, more than this. The theory of possession actually supplies us with a powerful method of co-ordinating and explaining many earlier groups of phenomena, if only we will consent to explain them in a way which at first sight seemed extreme in its assumptions—seemed unduly prodigal of the marvellous. Yet as to that difficulty we have learnt by this time that no explanation of psychical phenomena is really simple, and that our best clue is to get hold of some group which seems to admit of one interpretation only, and then to use that group as a point de repère from which to attack more complex problems.

Now I think that the Moses-Piper group of trance-phenomena cannot be intelligently explained on any theory except that of possession. And I therefore think it important to consider in what way earlier phenomena have led up to possession, and in what way the facts of possession, in their turn, affect our view of these earlier phenomena.

If we analyse our observations of possession, we find two main factors—the central operation, which is the control by a spirit of the sensitive's organism; and the indispensable prerequisite, which is the partial and temporary desertion of that organism by the percipient's own spirit.