544. The group of suggestive effects which we reach next in order is a wide and important one. The education of the central sensory faculties, of our power of inwardly representing to ourselves sights and sounds, etc, - is not less important than the education of the external senses. The powers of construction and combination which our central organs possess differ more widely in degree in different healthy individuals than the degrees of external perception itself. And the stimulating influence of hypnotism on imagination is perhaps the most conspicuous phenomenon which the whole subject offers; yet it has been little dwelt upon, save from one quite superficial point of view.

Every one knows that a hypnotised subject is easily hallucinated; - that if he is told to see a non-existent dog, he sees a dog, - that if he is told not to see Mr. A., he sees everything in the room, Mr. A. excepted. Common and conspicuous, I say, as this experiment is, even the scientific observer has too often dealt with it with the shallowness of the platform lecturer. The lecturer represents this induced hallucinability simply as an odd illustration of his own power over the subject. "I tell him to forget his name, and he forgets his name; I tell him that he has a baby on his lap, and he sees and feels and dandles it." At the best, such a hallucination is quoted as an instance of "mono-ideism." But surely to criticise thus is to judge something which is profound and complex from a merely external and accidental point of view. The hypnotiser's power over his patient is itself (telepathy apart) a mere result of suggestion. There may be a kind of delegation of that power by the subject to the hypnotiser, but all analogy shows us that it is really exercised by the subject over himself.

A truly hallucinable person can suggest to himself his own hallucinations with no external aid (see a case recorded by Dr. Wingfield in 518 D). "Mono-ideism," again, so far as it is ever a true description of the hypnotised subject's state, is a description only of its inhibitive and not of its dynamogenic aspect, - of what is not going on in his mind, rather than of what is going on. No mere inhibition will produce hallucinations. An ordinary person cannot feel a baby on his lap any the better for abstracting his attention from all objects of thought except babies. The real kernel of the phenomenon is not the inhibition but the dyna-mogeny; - not the abstraction of attention or imagination from other topics, but the increased power which imagination gains under suggestion; - the development of faculty, useless, if you will, in that special form of imagining the baby, but faculty mentally of a high order - faculty in one shape or another essential to the production of almost all the most admired forms of human achievement.

On this theme I shall have much to say; yet here again it will be convenient to defer fuller discussion until I review what I have termed "sensory automatism " in a more general way. We shall then see that this quickened imaginative faculty is not educed by hypnosis alone; that it is a part of the equipment of the subliminal self, and will be better treated at length in connection with other spontaneous manifestations. Enough here to have pointed out the main fact; for when pointed out it can hardly be disputed, although its significance for the true comprehension of hypnotic phenomena has been too often overlooked.

545. Yet here, and in direct connection with hypnotism, certain special features of hallucinations need to be insisted upon, both as partly explaining certain more advanced hypnotic phenomena, and also as suggesting lines of important experiment. The first point is this.

Post-hypnotic hallucinations can be postponed at will. The singular accuracy, indeed, with which they can sometimes be ordered for any given minute in the remote future will demand our attention when we are considering the stimulating effects of hypnotism on memory and intelligence. For the moment it is enough to note that post-hypnotic hallucinations afford a striking corroboration of the view here insisted on - namely, that it is an abiding element in the personality, - the subliminal self, or some fragment of the subliminal self, - which manufactures these quasi-percepts. Experience shows that a constant watchfulness is exercised, so that if, for example, the hypnotiser tells the subject that he will (when awakened) poke the fire when the hypnotiser has coughed three times, the awakened subject, although knowing nothing of the order in his waking state, will be on the look-out for the coughs, amid all other disturbances, and will poke the fire at the fore-ordained signal (see 551 A). Moreover, when the post-hypnotic suggestion is executed there will often be a slight momentary relapse into the hypnotic state, and the subject will not afterwards be aware that he has (for instance) poked the fire at all.

This means that the suggested act belongs properly to the hypnotic, not to the normal chain of memory; so that its performance involves a brief reappearance of the subliminal self which received the order.

546. Another characteristic of these suggested hallucinations tells in exactly the same direction. It is possible to suggest no mere isolated picture, - a black cat on the table, or the like, - but a whole complex series of responses to circumstances not at the time predictable. This point is well illustrated by what are called "negative hallucinations " or "systematised anaesthesiæ" Suppose, for instance, that I tell a hypnotised subject that when he awakes there will be no one in the room with him but myself. He awakes and remembers nothing of this order, but sees me alone in the room. Other persons present endeavour to attract his attention in various ways. Sometimes he will be quite unconscious of their noises and movements; sometimes he will perceive them, but will explain them away, as due to other causes, in the same irrational manner as one might do in a dream. Or he may perceive them, be unable to explain them, and feel considerable terror until the "negative hallucination" is dissolved by a fresh word of command.

It is plain, in fact, throughout, that some element in him is at work all the time in obedience to the suggestion given, - is keeping him by ever fresh modifications of his illusion from discovering its unreality (see e.g., in 546 A, Mrs. Sidgwick's experiments on the function of points de repère in negative hallucinations). Nothing could be more characteristic of what I have called a "middle-level centre " of the subliminal self, - of some element in his nature which is potent and persistent without being completely intelligent; - a kind of dream-producer, ready at any moment to vary and defend the dream.