Experimental psychology, of course, relies on experiments conducted under the eyes of the expert, for example, by hypnotism or otherwise, under Dr. Hack Tuke, Professor James, M. Richet, M. Janet. The evidence is the conduct rather than the statements of the subject. There is also physiological experiment, by vivisection (I regret to say) and post-mortem dissection. But non-experimental psychology reposes on the self-examination of the student, and on the statements of psychological experiences made to him by persons whom he thinks he can trust. The psychologist, however, if he be, as Mr. Galton says, 'unimaginative in the strict but unusual sense of that ambiguous word,' needs Mr. Galton's 'word of warning.' He is asked 'to resist a too frequent tendency to assume that the minds of every other sane and healthy person must be like his own. The psychologist should inquire into the minds of others as he should into those of animals of different races, and be prepared to find much to which his own experience can afford little if any clue.'[5] Mr. Galton had to warn the unimaginative psychologist in this way, because he was about to unfold his discovery of the faculty which presents numbers to some minds as visualised coloured numerals, 'so vivid as to be undistinguishable from reality, except by the aid of accidental circumstances.' Mr. Galton also found in his inquiries that occasional hallucinations of the sane are much more prevalent than he had supposed, or than science had ever taken into account. All this was entirely new to psychologists, many of whom still (at least many popular psychologists of the press) appear to be unacquainted with the circumstances. One of them informed me, quite gravely, that '_he_ never had an hallucination,' therefore--_his_ mind being sane and healthy--the inference seemed to be that no sane and healthy mind was ever hallucinated. Mr. Galton has replied to _that_ argument! His reply covers, logically, the whole field of psychological faculties little regarded, for example, by Mr. Sully, who is not exactly an imaginative psychologist.