617. The next step is one to which, as the reader of my chapter on hypnotism already knows, I attribute an importance much greater than is generally accorded to it. I refer to the hypnotiser's power not only of controlling but of inducing hallucinations in his subject.

These I have already described in some detail. I have noticed the facility of their production, their harmlessness, the advance which they show on ordinary imaginative power. Let us now consider them in relation to a wider field; as the outcome of central sensory stimulation - as the result of an empirical effort to guide and quicken the inner vision.

It is at once clear that the explanation of induced hypnotic hallucinations which is offered in ordinary handbooks is quite insufficient. As I have already said (in 544), the evocation of hallucinations is commonly spoken of as a mere example of the subject's obedience to the hypnotiser. "I tell my subject to raise his arm, and he raises it; I tell him to see a tiger in the room, and he sees one accordingly." But manifestly these two incidents are not on the same level, and only appear to be so through a certain laxity of language. The usage of speech allows me to say, "I will make my subject lift his arm," although I am of course unable to affect the motor centres in his brain which start that motion. But it is so easy for a man to lift his arm that my speech takes that familiar power for granted, and notes only his readiness to lift it when I tell him - the hypnotic complaisance which prompts him to obey me if I suggest this trivial action. But when I say, "I will make him see a tiger," I take for granted a power on his part which is not familiar, which I have no longer a right to assume. For under ordinary circumstances my subject simply cannot see a tiger at will; nor can I affect the visual centres which might enable him to do so.

All that I can ask him to do, therefore, is to choose this particular way of indicating that in his hypnotic condition he has become able to stimulate his central sensory tracts more powerfully than ever before. In his hypnotic complaisance he adopts my suggestion; he makes it a self-suggestion; he uses his newly developed faculty in the trivial manner which I desire. It is not my command, but his faculty, that is the kernel of the whole matter. Of what kind precisely, then, is the new capacity here involved?

Our discussion of hypnotism in the last chapter reviewed hypnotic increases of faculty of various kinds. First of all came that increase of profound organic faculty, of the vigour of the nutritive system, which lies at the base of psycho-therapeutics. Then came increase of sensibility to external stimuli; hypnotic hyperesthesia, or quickening of sight, hearing, taste, and smell; apparently capable of being pushed to an unknown degree. Then came a group of extensions of faculty to which I gave the general name of heteroesthesice. These were perceptions or discriminations of a novel kind; as of magnetic fields, or of the contact of specific metals. We could not, of course, determine whether these were stimulations of peripheral or of central sensibility: whether the end-organs transmitted a message from the outer world in novel terms, or whether the brain applied to a familiar message a novel delicacy of interpretation.

We then passed on to those exaltations of faculty which were definitely central, and which were no longer sensory, but affected rather the intellect or the moral sense. But in making this transition I passed quickly over a wide range of possible stimulations to faculty - such stimulations, namely, as might be applied to central sensory tracts; "quickening the imagination," as we say, and giving to images centrally initiated something more of that vividness to which only images from the external world can generally attain.

To this class of stimuli it is that our study of hallucinations now brings us back. And in another way these hallucinations connect themselves with an already traversed range of phenomena. The hallucinations with which we shall care to deal are not mere crude externalisations of some interior commotion, such as the flash of light with which the optic tracts respond to a blow on the head. They are in most cases elaborate products - complex images which must have needed intelligence to fashion them - although the process of their fashioning is hidden from our view. In this respect they resemble the inspirations of genius. For here we find again just what we found in those inspirations - the uprush of a complex intellectual product, preformed beneath the threshold, and projected ready-made into ordinary consciousness. The uprushing stream of intelligence, indeed, in the man of genius flowed habitually in conformity with the superficial stream. Only rarely does the great conception intrude itself upon him with such vigour and such untimeliness as to bring confusion and incoherence into his ordinary life. But in the case of these induced hallucinations the incongruity between the two streams of intelligence is much more marked.

When a subject, for instance, is trying to keep down some post-hypnotic hallucinatory suggestion, one can watch the smooth surface of the supraliminal river disturbed by that suggestion, as though by jets of steam from below, which sometimes merely break in bubbles, but sometimes force themselves up bodily through the superficial film.