More insidious and more difficult to guard against are errors of memory. There is a natural and almost inevitable tendency to dramatic unity and completeness which leads to the unconscious suppression of some details, and the insertion of others. Probably of all errors due to this cause a nice adjustment of the dates is the commonest. In perhaps the majority of second-hand cases, and in some of the more remote first-hand narratives, the coincidence is said to be exact to the minute. "At that very moment my friend passed away" is a common phrase. As a matter of fact, in the best attested recent cases it can rarely be shown that the coincidence is precise, and the impression frequently follows the death by some hours. But there is risk also of the actual transformation of the experience itself. A dream after the lapse of years will be recalled as a hallucination,[75] a vague feeling of discomfort as a vivid emotion, or even a mental vision; a hallucination not recognised at the moment will in the retrospect seem to have been identified with some person who died at about that time; and details, such as clothes worn or words spoken by the phantom, will be borrowed from later knowledge and read back into the image preserved in the memory. There will further be a gradual simplifying and rounding off of the incident, a deepening of the main lines, and a suppression of what is not obviously relevant or coherent. With many persons there can be no doubt that this process is almost, if not wholly, unconscious; and it need hardly be said that in that very fact lies the special danger against which we have to guard.[76]
As an instance of the gradual approximation of dates, I may cite a case recorded in the Proceedings of the American S.P.R. (pp. 401, 527). The narrator wrote to Dr. Hodgson:—"I once dreamed that W. T. H. was dead; and the same night he was thrown down several feet on to an engine, ... when he was taken up it was thought he was dead." From later inquiries it was ascertained that the accident did indeed occur as alleged—but a week or ten days after the dream![77] As an illustration of a different kind of metamorphosis, a case may be given which I recently received from a lady and her daughter—an account of a "ghost" seen twenty-five years ago by the latter and her nurse. The younger lady described to me the figure seen; the mother told me that she had received a similar description from both nurse and daughter at the time of the incident. Both ladies were clear-headed and sensible witnesses, and it was impossible to doubt that they believed what they said. But in her childish diary, which the younger lady kindly unearthed for my inspection, the only entry referring to the matter—an entry written in pencil and obviously as an afterthought—ran: "Ellen saw a ghost." If the diarist had herself shared the experience, it is difficult to believe that even the modesty natural to her age and sex would have withheld her from recording the fact for her private glorification.
It would be easy to multiply cases of this kind. But those who demand most proof of the action of telepathy will probably be least exacting of evidence for the untrustworthiness of ancient memories. As a matter of fact, we have the evidence of statistics to show that the imagination does tend after a certain lapse of time to magnify coincidences in matters of this kind, and even to invent coincidences where none existed. It will be shown in Chapter IX., in the discussion on the results obtained from an inquiry into the distribution of sensory hallucinations, that whereas non-coincidental hallucinations tend to be forgotten after the passing of a few years, the records of coincidental hallucinations—or at least of those which are alleged to have coincided with the death of the person seen—are proportionately more frequent ten years ago than at the present time, the inference being that a certain number of coincidences have been unconsciously improved or invented in the interval.
Pseudo-presentiment.
In a letter published in Mind (April 1888) Professor Royce, of Harvard, U.S.A., hazarded a hypothesis that there may occur "instantaneous and irresistible hallucinations of memory which make it seem to one that something which now excites or astonishes him has been prefigured in a recent dream, or in the form of some other warning." In support of that hypothesis Professor Royce appeals to the analogy of the well-known cases of double memory,—the impression of having at some previous time looked on a scene now present, or heard a conversation now taking place; and to two or three instances of undoubted hallucination of memory amongst the insane, recorded by Krafft-Ebing and Kraepelin. As regards the latter, it is sufficient to remark that the hallucinations occurred to persons whose minds were admittedly diseased; that the hallucinations themselves were apparently slow of growth, whereas the hypothesis requires that they should be more or less instantaneous; and that in other respects they do not present by any means a perfect parallel to the presumably telepathic cases with which he compares them. In default, therefore, of more precise analogies, the hypothesis of pseudo-presentiment must be regarded as, at best, a plausible guess. And even if it were fully substantiated it would only, as pointed out by Mr. Gurney (Mind, July 1888), apply to certain classes of telepathic cases, and those the weakest from the evidential standpoint. At most the theory would account for dreams and indefinite impressions of various kinds not mentioned beforehand. In some cases of this kind, and in a large class of so-called "prophetic" dreams, I am inclined to regard Mr. Royce's explanation as possibly true, in the modified form suggested by Dr. Hodgson (Proc. American S.P.R., pp. 540 et seq.)—i.e., if it is restricted to cases where there is a vague memory of some actual dream or other impression, bearing a more or less remote resemblance to the event; in other words, if we assume an illusion rather than a hallucination of memory. But it need hardly be said that no serious investigator would treat the uncorroborated accounts of dreams and vague feelings of this kind as evidence for anything whatever. To extend the hypothesis, as Professor Royce suggests, to cases where there is evidence that the percipient's experience was mentioned beforehand, is to suppose not one kind of pseudo-memory, but two,—a pseudo-memory on the part of the percipient that he has had a certain subjective experience, and a pseudo-memory on the part of some other person that this experience was mentioned to him before the news of the event to which it related. In recent cases, at any rate, the assumption of a double mistake of this kind seems unwarranted.[78] And to apply this explanation to cases of actual sense-hallucination involves even more violent improbabilities. It would require far more evidence than Professor Royce can offer to make it credible that a man on hearing of the death of a friend should straightway be capable of imagining that at a definite hour and in a particular place he had seen an apparition of that friend, when in fact he had had no experience of the kind. It is remarkable that Mr. Royce does not himself appear to have realised the distinction between the two kinds of impressions.
Precautions against Error.
We have now to consider by what methods the various defects incident to testimony on these matters may be best eliminated. As the evidence upon which reliance is placed will be illustrated by the examples quoted hereafter, it will not be necessary to dwell at length here upon the precautions taken. The testimony at first-hand of the actual witnesses, it need hardly be said, is to be desired in any investigation; but in the case of phenomena which are at once stimulating to the imagination, and, as being novel, have no recognised standard of probability by which narrator or auditor can check deviations from the truth, no other evidence is worthy of consideration.[79] It will be seen that in all the cases here quoted the witness, or one of the witnesses, has furnished an account of his experience written by himself;[80] and it is worth noting that the very act of writing such an account to serve the purpose of a systematic inquiry is calculated to inspire the percipient with a sense of responsibility, and to lead him to weigh his words with precision. I may add that by the courtesy of our informants we have in most cases been enabled to question them orally on the details of their experience.[81]
But, for reasons already given, no case should be suffered to rest upon a single memory. It is of the highest importance, therefore, to obtain the corroborative testimony of persons who were cognisant of the occurrence of the impression before the news of the corresponding event. When this is not to be obtained, evidence of some unusual action on the part of the percipient, such as the taking of a journey, or the putting on of mourning, may be accepted as collateral proof of the reality of his impression. But, as we have already seen, the evidence of the attesting witnesses is liable to the same errors which affect the testimony of the percipient; and the evidence most to be desired is of a kind exempt from these weaknesses—that of a letter or memorandum written before the news. In a large proportion of the narratives dealt with, it is asserted that such a letter was written, or such a memorandum made. Unfortunately, this alleged documentary evidence is rarely forthcoming. It is possible that in some cases this statement is merely a conventional dramatic tag,—an addition made unconsciously and in perfect good faith to round off the story.[82] It cannot, however, I think, be regarded as surprising either that a letter or note was not written at the time, or that, if written, it should not have been preserved. Sensory hallucinations—to take the most striking instance—though unusual are not extremely rare experiences; most educated persons are perfectly familiar with the fact of their occurrence and regard them (in most cases rightly) as purely subjective, the products of some transient cerebral disturbance, as little worthy of record as a headache or a bilious attack. Often, probably, the telepathic hallucination is indistinguishable from the mass of purely subjective experiences of the same kind; and even should it be recognised at the time as exceptional, the want of leisure, the fear of ridicule, even the dislike of seeming to admit to himself the possibility of his experience having a sinister significance, would probably deter the percipient from writing about it.[83] It is much more likely that he would speak of it to an intimate friend, should opportunity occur. And when in the rare conjunction of an exceptional experience, adequate leisure, and a sympathetic correspondent, or the habit of writing a diary, the letter is actually written or the note made, the chances which militate against its preservation are many. Few persons will take a general and impersonal (in other words, a scientific) interest in occurrences of this kind. Their own isolated experience may possess a deep and abiding interest for themselves, and, less certainly, for their friends; an interest, however, which is quite compatible with the treatment of the attesting record as waste paper. But unless it can be used to illustrate or support a theory of a future life, they seldom regard a "ghost story" as having any value other than that derived from the personal environment. It appears, indeed, to possess for most little more significance than the recital of an extraordinary run of luck at cards, or a fortunate escape from a railway accident, between which it is commonly sandwiched. Again, few persons realise the high value of contemporary documentary evidence in matters of the kind; there are many who would probably share the views of a courteous correspondent, who, after sending me condensed copies of some contemporary memoranda, wrote in answer to my inquiries:—"I have not got the originals; I destroyed them immediately I sent them (i.e., the copies) to you, because I knew they would be more permanently preserved and recorded; being authenticated to Professor Barrett and you, there was no further need of them." And even when they escape immediate destruction the letters may, as in cases reported to us, be "washed out" or burnt; or may survive the perils of flood and fire only to be mislaid, so that they cannot be found without a more thorough search than the courtesy of our correspondents can induce them to make. Notwithstanding these various adverse chances, it will be found that many of the narratives which follow are actually attested by contemporary documentary evidence.
When the great mass of narratives has been carefully examined and tested in the light of the considerations above set forth, and when all those which are remote in date, or for some other reason suspect, have been eliminated, there will be found to remain an important body of testimony. And of this sifted residue, though we cannot predicate of any single narrative that it accurately represents the facts, or that the coincidence with which it deals was not purely casual, yet looking at the cases as a whole, we may feel a reasonable assurance that in their essential features the facts are correctly reported, and that the coincidences are not due to chance.