Those who undertake the scientific consideration of psychic phenomena must realize the existence of certain initial difficulties specially attached to this branch of research. No form of scientific work is more exposed than this to the dangerous influence of the “personal equation” in the researcher. An astronomer might conceivably be prejudiced in his work on Mars by some _a priori_ tendency to regard that planet as the home of sentient beings, but the influence of such personal factors in scientific research may generally be regarded as almost negligible. When, however, we find ourselves in contact with psychic phenomena which indicate intelligence, it is often difficult to dissociate our conclusions as to the source of such intelligence from our other beliefs or disbeliefs. On an occasion famous in the annals of the Society for Psychical Research a sealed envelope containing a written statement by the late F. W. Myers was opened in order to test the accuracy of Mrs Verrall’s automatic ‘Myers’ script, which had previously claimed to reveal the words of the sealed message. I shall never forget the look of cruel disappointment which appeared on the faces of some of those present when the two messages were found to be dissimilar. On the other hand one of the party, a persistent opponent of the spiritist hypothesis, received the result with obvious satisfaction. That such preconceived hopes or opinions colour the general attitude of the devotees of popular and uncritical spiritualism is obvious. Given a dark room, a professional medium inadequately controlled or uncontrolled and a cardboard trumpet, the voice which comes through the trumpet is, to a large extent, accepted as that of a discarnate friend because the sitters are already convinced of a survival or earnestly desire to be so convinced. Even in the later work of psychical researchers of a higher order, men of intellectual eminence and scientific training, a certain relaxation of critical rigidity is sometimes noticeable. In these cases the lapse from earlier standards of evidence is no doubt due to the absolute conviction secured by long and critical investigations at some previous period. When already convinced intellectually by earlier experiences of the reality of the phenomena under investigation, even men of the mental calibre of a Sir William Crookes may almost insensibly deviate in subsequent discussions from the evidential standard of the investigations from which they derived their earlier conclusions.