Both among civilized and uncivilized peoples there is a widespread belief that the apparition of a living person is an omen of death; but until the Society for Psychical Research undertook the statistical examination of the question, there were no data for estimating the value of the belief. In 1885 a collection of spontaneous cases and a discussion of the evidence was published under the title Phantasms of the Living, and though the standard of evidence was lower than at the present time, a substantial body of testimony, including many striking cases, was put forward.
In 1889 a further inquiry was undertaken, known as the Census of Hallucinations, which provided information on the percentage of individuals in the general population who, at some period of their lives, while they were in a normal state of health, had had involuntary extrasensory impressions. These included a vivid impression of seeing or being touched by a living being or inanimate object, or of hearing a voice; which impression, so far as they could discover, was not due to any external cause. About 17,000 answers were received and after making all deductions it appeared that death coincidences numbered about 30 in 1300 cases of recognized apparitions; or about 1 in 43. If chance alone operated the coincidences would have been in the proportion of I to 19,000. As a result of the inquiry the committee deemed that a connection exists between deaths and apparitions of the dying person, which is not due to chance alone.
From an evidential point of view the apparition is the most valuable class of death-warning . Recognition is more difficult in the case of an auditory hallucination, even where it takes the form of spoken words; moreover, auditory hallucinations coinciding with deaths may be mere knocks, ringing of bells, etc. Tactile hallucinations are still more difficult to recognize; and the hallucinations of smell which are sometimes found as death-warnings rarely have anything special to associate them with the dead person. Occasionally the death-warning is in the form of an apparition of some other person; it may also take the form of a temporary feeling of intense depression or other massive sensation.