Prick or pinch the hypnotised subject, and although some stratum of his personality may be aware, in some fashion, of your act, the sleep will generally remain unbroken. But if you speak to him,--or even speak before him,--then, however profound his apparent lethargy, there is something in him which will hear.[65] All this is true even of earlier stages of trance. Deeper still lies the stage of highest interest;--that sleep-waking in which the subliminal self is at last set free,--is at last able not only to receive but to respond: when it begins to tell us the secrets of the sleeping phase of personality, beginning with directions as to the conduct of the trance or of the cure, and going on to who knows what insight into who knows what world afar? Without, then, entering into more detail as to the varying forms which hypnosis at different stages may assume, I have here traced its central characteristic;--the development, namely, of the sleeping phase of personality in such fashion as to allow of some supraliminal guidance of the subliminal self. We have here a definition of much wider purview than any which has been habitually applied to the process of hypnotisation or to the state of hypnosis. To test its validity, to explain its scope, we need a survey of hypnotic results much wider in range than any enumeration of the kind at present usual in text-books. Regarding hypnotic achievements mainly in their _mental_ aspects, I must seek for some broad principle of classification which on the one hand may not be so exclusively moral as to be physiologically untranslatable,--like the distinction between vice and virtue;--or on the other hand so exclusively physiological as to be morally untranslatable,--like the distinction between cerebral anæmia and hyperæmia. Perhaps the broadest contrast which is expressible in both moral and physiological terms is the contrast between check and stimulus,--between _inhibition_ and _dynamogeny_. Not, indeed, that such terms as _check_ and _stimulus_ can be pressed in detail. The central power,--the ruling agency within the man which gives the command,--is no doubt the same in both cases. But the common contrast between negative and positive exhortations,--"this you shall _not_ do," "this you _shall_ do,"--will help to give clearness to our review of the influences of hypnotism in its bearings on intelligence and character,--its psychological efficacy. The most rudimentary form of restraint or inhibition lies in our effort to preserve the infant or young child from acquiring what we call "bad tricks." These morbid affections of motor centres, trifling in their inception, will sometimes grow until they are incurable by any régime or medicament;--nay, till an action so insignificant as sucking the thumb may work the ruin of a life.