There is, indeed, much to be said in favour of Michel-son's point of view, although his contention may not repose on an entirely sound basis. We must also admit that the experimenter is frequently in anything but a position to exclude the action of suggestion. Consequently, it would be wrong to consider that all the earlier psychological experiments in which suggestion possibly played a part were simply superfluous; many of them would probably give the same results if suggestion were excluded. If, however, one is unable in every single instance to carry out the most extreme precautionary measures, one must at least be careful so to do before venturing on far-reaching conclusions. We should take Laplace's words to heart, and examine phenomena with all the greater care in proportion to the difficulty we have in accepting them. This principle should guide us in respect to the exclusion of the action of suggestion. An event which at the time of its occurrence created a considerable commotion (I refer to the case of Clever Hans), will show how far we may be led by neglecting the above lesson taught us by hypnotism.

If the Berlin psychologist Stumpf, the scientific director of the committee of investigation, had but taken into consideration the teachings of hypnotism he would never have made the fiasco of admitting that the horse, Clever Hans, had been educated like a boy, not trained like an animal.

Clever Hans answered questions by tapping his hoof on the stage; and the observers, more particularly the committee presided over by Stumpf, believed that the answers tapped out were the result of due deliberation on the part of the horse, exactly as spiritists believe that the spirits hold intelligent intercourse with them by means of "raps." One tap denoted 0, two taps b, three taps c, etc.; or, where numbers were concerned, one tap signified 1, two taps 2, etc. In this way the animal answered the most complicated questions. For instance, it apparently not only solved such problems as 3 times 4 by tapping 12 times, and 6 times 3 by tapping 18 times, but even extracted square roots, distinguished between concords and discords, also between ten different colours, and was able to recognize the photographs of people; altogether, Clever Hans was supposed to be at that time about upon a level with a fifth-form 1 boy. After investigating the matter, Stumpf and the members of his committee drew up the following conjoint report, according to which only one of two things was possible - either the horse could think and calculate independently, or else he was under telepathic, perhaps occult, influence: -

The undersigned met together to decide whether there was any trickery in the performance given by Herr v. Osten with his horse - i.e., whether the latter was helped or influenced intentionally. As the result of the exhaustive tests employed, they have come to the unanimous conclusion that, apart from the personal character of Herr v. Osten, with which most of them were well acquainted, the precautions taken during the investigation altogether precluded any such assumption. Notwithstanding the most careful observation, they were unable to detect any gestures, movements, or other intimations that might serve as signs to the horse. To exclude the possible influence of involuntary movements on the part of spectators, a series of experiments was carried out solely in the presence of Herr Busch, Councillor of Commissions. In some of these experiments, tricks of the kind usually employed by trainers were, in his judgment as an expert, excluded. Another series of experiments was so arranged that Herr v. Osten himself could not know the answer to the question he was putting to the horse. From previous personal observations, moreover, the majority of the undersigned knew of numerous individual cases in which other persons had received correct answers in the momentary absence of Herr v.

Osten and Herr Schillings. These cases also included some in which the questioner was either ignorant of the solution or only had an erroneous notion of what it should be. Finally, some of the undersigned have a personal knowledge of Herr v. Oiten's method, which is essentially different from ordinary "training" and is copied from the system of instruction employed in primary schools. In the opinion of the undersigned, the collective results of these observations show that even unintentional signs of the kind at present known were excluded. It is their unanimous opinion that we have here to deal with a case that differs in principle from all former and apparently similar cases; that it has nothing to do with "training" in the accepted sense of the word, and that it is consequently deserving of earnest and searching scientific investigation. Berlin, Sept. 12th, 1904. (Here follow the signatures, among which is that of Privy Councillor Dr. C. Stumpf, University Professor, Director of the Psycho-l)gical Institute, Member of the Berlin Academy of Sciences.)

1 Lowest form but one in a German gymnasium.

Any one who has done critical work in the domain of hypnotism, after the manner insisted on by the Nancy school, cannot help considering Stumpfs method of investigation erroneous from the very outset. I had visited Herr v. Osten, the owner of Clever Hans, more than a year before Stumpf wrote his deplorable report; and, on the ground of my experiences in the domain of hypnotic experiment and suggestion, I had at once thought of those signs, which we make unintentionally and subconsciously, as primary sources of error. I therefore at once so arranged the conditions of the experiments that no one present, not even myself, could know the correct result. In consequence of this every experiment turned out a failure, as I explained to the Psychological Society of Berlin at a time when Stumpf had not yet retreated from his erroneous position. A first source of error that had to be considered was that some one present - it might have been Herr v. Osten or it might have been any one else - unintentionally gave the horse a sign when to stop tapping. It cannot be considered sufficient, as stated in Stumpf's report, that Herr v. Osten did not know the answer; no one should be present who knows it. This is the first condition to be fulfilled when making such experiments.