The place which the explanation of spiritualistic and theosophic manifestations occupies in Psychical Research has already been noted; that of ghosts and rappings and haunted houses and _poltergeists_ is quite similar. Not wholly yet measurably different is the status of the study of hallucinations, presentiments, and previsions or premonitions. In this entire group of phenomena, the interests of Psychology and of Psychical Research are in the main distinct. This is readily illustrated with reference to the study of hallucinations. These are interesting to the psychologist quite in the same sense as any other natural product of psycho-physiological action; the prevalence of hallucinations under fairly normal conditions presents one out of a large number of interesting details, and forms a proper investigation for the Society for Psychical Research. Their census of hallucinations hardly bears out the conclusions which have been drawn therefrom, but contains much interesting information. When, however, the emphasis of the investigation is placed upon "veridical" hallucinations, and the establishment of the conclusion that so many more of these hallucinations and presentiments "come true," or have a mysterious significance, than chance would allow, then the psychological interest is quite obscured by an interest of a totally different character. A "veridical" hallucination has little psychological pertinence; for it is equally interesting psychologically whether it happens to come true or not. The bearing of the hallucination upon or its origin in some of the occupations of normal waking life; the possibility of its interpretation as a peculiar retroactive illusion of memory, as Professor Royce has suggested for some cases; its significance as an unconscious perception of the shadow already present, not yet visible to consciousness, but coming before the event,--such are significant characteristics of hallucinations. The results of the study of hallucinations may likewise be applied to a determination of their relation to the sum total of the sequences of consciousness that constitute our mental life; but there is only a most incidental psychological interest in the apparently personally significant or "veridical" aspect of the phenomena. And furthermore, whether they are truly "veridical" or only seemingly so; whether, in other words, there is evidence enough in quality and quantity to make it a proper scientific inquiry as to the existence of a cause-and-effect-like relation between presentiment and issue,--this is a logical inquiry, although one which, along with other factors, includes psychological considerations.