When the witness is not isolated, but is a member of a group, the defects we have before noted, due to the creative imagination, are likely to be accentuated. The event will have been discussed and a uniform version gradually prepared. It is almost impossible, from the unanimous testimony of a number of witnesses who have been in consultation, to extract the original perceptions. The phenomenon of _mimétisme testimonial_ makes its appearance, and may assume abnormal dimensions. A kind of collective hysteria may be induced, and there can be little doubt that some of the collective denunciations of witches which took place in the Middle Ages were manifestations of this form of mimicry. Such are some of the results that have been reached by the modern investigations of the value of human testimony. They tell us little we did not know before, for mankind has had an immense experience of human testimony; but they make our knowledge more precise and enable us to see what kinds of testimony are most open to suspicion. The effect of these researches on judicial procedure should be considerable, and their influence on the study of history not less marked. On this latter subject their influence can only be indirect, and in the direction, probably, of throwing still more doubt on the accuracy of historical records. The “credibility” of a witness still remains a vague quantity, but the chances are that it is something less than the value hitherto assigned to it. The investigation can claim no such precise results as those enunciated by Craig in 1699 in his _Theologiæ Christianæ Principia mathematica_, where, after proving that the suspicions of any history vary in the duplicate ratio of the times taken from the beginning of the history, he shows that faith in the Gospel, so far as it depended on oral tradition, expired about the year 880, and, so far as it depended on written tradition, would expire in the year 3150. The new investigations of the value of human testimony start from humbler, but surer, foundations. _Printed in Great Britain by_ Butler & Tanner, _Frome and London_ =TRANSCRIBER’S NOTES= Simple typographical errors have been silently corrected; unbalanced quotation marks were remedied when the change was obvious, and otherwise left unbalanced. Punctuation, hyphenation, and spelling were made consistent when a predominant preference was found in the original book; otherwise they were not changed.