The persistent belief on the part of the narrators in the genuineness of their previsions indicates that in some cases there may be a hallucination of memory, analogous to the well known feeling of "false recognition."
To the first belong what may be called the physical phenomena (q.v.) of spiritualism - those, namely, which, if correctly observed and due neither to conscious or unconscious trickery nor to hallucination or illusion on the part of the observers, exhibit a force acting in the physical world hitherto unknown to science.
Among proposed normal explanations of these phenomena that of hallucination (q.v.), including illusion as to what is seen almost amounting to hallucination, deserves careful consideration.