We have the obverse of this post-hypnotic suggestion in the phenomenon of double consciousness. A subject is hypnotised and becomes somnambulistic; when he is waked, he has no memory whatsoever of the events that occurred during the hypnotic state. Later, he is hypnotised again; and now it turns out that he remembers what took place during the previous hypnosis. So he seems to have a double consciousness; the normal waking consciousness, which is sensibly continuous in his waking states, and a secondary hypnotic consciousness, which is continuous from one state of somnambulism to another. There is, again, nothing mysterious in the facts; we have their parallel in the normal shifts of personality; we have seen that a man is a different self in the office, on the golf-links, with his children in the nursery; and we have now only to add that the known laws of memory are adequate to these phenomena of double consciousness. For we do not pass in thought from one situation to another unless the situations are connected by some idea which is common to them both; the hard-worked professional man, when he is on the links, forgets the office; that is the reason for his play; and he forgets the office because there is no community of ideas between his work and his recreation. In hypnosis, too, we break sharply with the waking life; if the two are to be connected, a bridge must be built ad hoc by the operator; but when we relapse into hypnosis we pick up again the thread of our hypnotic memory, as naturally as the professional man picks up his work when he seats himself at his desk after a half-holiday.
There are still a couple of questions, often asked by students, that you may care to have answered; and the first of them usually takes the form: Can a man be hypnotised against his will? To which the author’s reply always is: It depends on what you mean by ‘against his will.’ For consider! There is no reason at all why we may not, any one of us, be taken off guard and surprised into the hypnotic state. We have probably all been surprised by sleep during a lecture or a sermon; the conditions were favourable, and we nodded. So the conditions may be favourable for hypnosis; and if someone is watching us, and sees that the conditions are favourable, he may have us hypnotised before we know where we are. The risk is not great; but the possibility is there. Again, if a patient has fallen into the habit of taking hypnotic treatment, and if he has thus slipped into a position of invalidish dependence upon his physician, so that obedience to the suggestion of hypnosis has become natural to him, then it is entirely likely that the physician’s command would induce the hypnotic state, even if the patient at the time should not desire it. And what holds of physician and patient holds of any operator and any subject in like circumstances; the habit of obedience grows by obeying. In this sense, then, one might be hypnotised ‘against one’s will.’ If, however, the question means what it is probably intended to mean: Can another man come to me and, by virtue of some inherent power, force me into hypnosis in spite of my resistance to that suggestion? then the answer is No; no more than a man can force you to lend him money or to perjure yourself for him in a court of law. It is you who must entertain his suggestion; so long as you refuse to do that, you are immune to hypnosis at his hands.
The other question concerns the value of hypnosis for medical or therapeutic purposes; can hypnosis effect cures? can it replace the anæsthetics of ordinary medical practice? It has, as a matter of fact, received fairly extended trial as an anæsthetic; and while it has allowed many operations, minor and major, to be carried out successfully, it is far less reliable than the an æsthetic drugs; mainly, no doubt, because it cannot be administered by the physician, as drugs can, but depends upon the attitude of the patient himself. There is no future for hypnosis in this connection. As to its therapeutic value, we can only say that whatever can be accomplished by suggestion, in the normal life, can be accomplished by the very strong suggestion of hypnosis in the disordered life. A suggestion can initiate, modify, and arrest movement; a sharp rebuke will start a child into activity, or change his occupation, or stop a present misdeed and prevent like misdeeds in the immediate future. A suggestion, again, can make us blush; and a suggestion can make us cry. Here, then, is the therapeutic value of hypnosis; it may arrest or remedy habits like alcoholism, and it may act upon derangements of circulation and secretion. Farther than this it cannot go; and even within these limits its utility is variable. Some children obey the first word of command, and others must be bidden over and over again before they do as they are told; some of us blush easily, and some hardly ever; some are readily stirred to tears, and some with great difficulty. So it is with the liability to hypnotic suggestion; everyone is liable, but not everyone to the same degree. Besides, as we saw just now, the habit of hypnosis grows, like all habits, upon him who has formed it; the patient may develop a craving for the hypnotic treatment, and in this way may take on a habit of dependence, of constant reliance upon others, which is as afflicting and demoralising as the disorder which the treatment was meant to cure. So that, on the whole, hypnosis should not be lightly appealed to; the decision should in every case remain in the hands of the experienced physician.
There is one other effect of hypnosis that we have not spoken of in detail, and that is of great psychological interest; the somnambulist, we said, will perceive as the operator wishes him to perceive, will take coal for sugar and ink for wine. It has long been debated whether this statement is literally true. The hypnotised subject behaves as if he perceived the sugar and the wine; but is there any reason to think that he actually perceives them? Or if the suggestion is negative, and the subject is told that a certain person has left the room, he will behave as if that person were no longer present; but does he actually fail to see him? May not the suggestion bear directly upon the subject’s conduct, and leave his perceptions unchanged? The facts point in both directions. Many of the apparent changes of perception are, in all probability, nothing more than changes of behaviour towards the perceptual stimuli; but there is, all the same, no impossibility in a change of perception itself. We have already noted the negative effects of abstraction (p. 281); and recent experiments with normal subjects seem to show conclusively that a suggestion, a form of words that carries the force of a command, may set up the mental process, or the change of mental processes, normally correlated with presence or change of external stimulus. A red, seen under the suggestion of blue, will not only be reported as bluish, but will actually look bluish; and a thermally indifferent impression will not only be reported as warm or cold, but will actually be felt warm or cold. If such things happen in the normal waking life, they may assuredly happen in the narrowed and intensive suggestibility of the hypnotic state.
A. Moll, Hypnotism, 1891; W. Wundt, Lectures on Human and Animal Psychology, 1896, Lect. xxii.; M. de Manacéïne, Sleep, 1897; J. Jastrow, Fact and Fable in Psychology, 1900; E. Jones, Freud’s Theory of Dreams, in American Journal of Psychology, xxi., April 1910, 283 ff.; S. Ferenczi, The Psychological Analysis of Dreams, ibid., 309 ff.; M. Bentley, The Study of Dreams, ibid., xxvi., April 1915, 196 ff.