The hint which I have to offer here involves, I hope, something more than a mere change of appellation. I define suggestion as "successful appeal to the subliminal self";--not necessarily to that self in its most central, most unitary aspect; but to some one at least of those strata of subliminal faculty which I have in an earlier chapter described. I do not indeed pretend that my explanation can enable us to reduce hypnotic success to a certainty. I cannot say why the process should be so irregular and capricious; but I can show that this puzzle is part and parcel of a wider mystery;--of the obscure relationships and interdependencies of the supraliminal and the subliminal self. In split personalities, in genius, in dreams, in sensory and motor automatisms, we find the same fitfulness, the same apparent caprice. Leaving perforce this problem for the present unsolved, let us consider the various ways in which this conception of subliminal operation may throw light on the actual phenomena of hypnotism;--phenomena at present scattered in bewildering confusion. The word _hypnotism_ itself implies that some kind of _sleep_ or trance is regarded as its leading characteristic. And although so-called hypnotic suggestions do often take effect in the waking state,[64] our usual test of the hypnotiser's success lies in the slumber--light or deep--into which his subject is thrown. It is, indeed, a slumber which admits at times of strange wakings and activities; but it is also manifestly profounder than the sleep which we habitually enjoy. If sleep, then, be the phase of personality specially consecrated to subliminal operation, it follows that any successful appeal to the subliminal self will be likely to induce some form of sleep. And further, if that form of sleep be in fact not an inevitable result of physiological needs, but a response to a psychological appeal, it seems not unlikely that we should be able to communicate with it without interrupting it;--and should thus be able to guide or supplement subliminal operations, just as in genius the subliminal self guided or supplemented supraliminal operations. Now I hold that in all the varied trances, lethargies, sleep-waking states, to which hypnotism introduces us, we see the subliminal self coming to the surface in ways already familiar, and displacing just so much of the supraliminal as may from time to time be needful for the performance of its own work. That work, I say, will be of a character which we know already; the difference is that what we have seen done spontaneously we now see done in response to our appeal.