So far we have been considering the witness in isolation, and we have not considered the reaction upon his testimony of the emotional state produced in him by the event. Yet the emotions accompanying the event have a great bearing upon the value of the witness’s testimony. During the war it was noticed that the evidence of soldiers freshly wounded was often of the most fantastic description. They would testify to the details of catastrophes which had never occurred; they would assert that so-and-so had been decapitated in front of their eyes, and so-and-so buried by an explosion, when, as a matter of fact, nothing remotely resembling these events had taken place. And, under the influence of the comparatively slighter emotions of a spiritualistic séance, people will identify the same “materialised” mask as the features of their husbands, wives, sons, daughters. Under the influence of such emotions it may be taken as a general rule that perceptions deteriorate, and illegitimate inference, “unconscious reasoning,” becomes more marked. Unconscious reasoning, indeed, plays a very great part in nearly all cases of mal-observation. It is well exemplified in the statement of the man sitting in a dark wood: “That dog’s bark is not really a grasshopper, it is the squeaking of a cart.” And Dr. Locard tells of one experiment he made, while in the Army, with a barometer which bore a remote resemblance to a clock. His suggestion that it was a clock was invariably accepted, even by the most eminent people, and several of them acquired their knowledge of the time of day from its indications, even when the hour so indicated was highly improbable. The testimony of great and commanding figures, even to the time of day, may therefore be open to suspicion. But the immense part played by unconscious reasoning is best seen in the psychology of conjuring, under which head it is fair to group the great majority of alleged spiritualistic phenomena. In this latter case we have further to recognise what Freud calls the “pleasure-pain principle,” as distinguished from the “reality-principle.” In other words, the witnesses are seldom disinterested; they strongly desire to witness certain events rather than others, and in such cases the slightest suggestion is sufficient to produce conviction.