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. References 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. INDEX OF NAMES Angelo, M., 299. Aristotle, 25, 41, 84, 142 f., 145 ff., 168, 175, 218, 305. Arnold, M., 305. Bacon, F., 34, 313. Bain, A., 229, 257, 260, 324, 334. Baldwin, J. M., 41, 72, 89, 334. Barrie, J. M., 247. Bastian, H. C., 72. Beethoven, L. van, 196. Bentley, M., 349. Bergson, H., 229. Berkeley, G., 264, 289. Blagden, C. O., 72. Boas, F., 303, 306. Bradley, F. H., 174, 176. Bridgman, L., 27, 41. Buridan, J., 247. Burr, A. R., 39. Cannon, W. B., 220 f., 229. Carpenter, W. B., 108 f., 111. Carroll, L., 21. Charcot, J. M., 139, 143. Chavannes, P. de, 196. Clifford, W. K., 38. Dalton, J., 58, 72. Darwin, C., 3, 51, 222 f., 225, 228 f. Da Vinci, L., 228. Deland, M., 175. Descartes, R., 228.