I. It may include events once known to the waking self, but now definitely forgotten.
II. It may include facts which have fallen within the sensory field, but which have never been supraliminally "apperceived" or cognised in any way. And thus also it may indicate that from this wider range of remembered facts dream-inferences have been drawn;—which inferences may be retrospective, prospective, or,—if I may use a word of Pope's with a new meaning, circumspective,—that is to say, relating not to the past or to the future, but to the present condition of matters beyond the range of ordinary perception. It is plain that inferences of this kind (if they exist) will be liable to be mistaken for direct retrocognition, direct premonition, direct clairvoyance; while yet they need not actually prove anything more than a perception on the part of the subliminal self more far-reaching,—a memory more stable,—than is the perception or the memory of the supraliminal self which we know.
These hypermnesic dreams, then, may afford a means of drawing our lines of evidence more exactly; of relegating some marvellous narratives to a realm of lesser marvel, and at the same time of realising more clearly what it is in the most advanced cases which ordinary theories are really powerless to explain.
As to the first of the above-mentioned categories no one will raise any doubt. It is a familiar fact—or a fact only sufficiently unfamiliar to be noted with slight surprise—that we occasionally recover in sleep a memory which has wholly dropped out of waking consciousness.
In such cases the original piece of knowledge has at the time made a definite impress on the mind,—has come well within the span of apprehension of the supraliminal consciousness. Its reappearance after however long an interval is a fact to which there are already plenty of parallels. But the conclusion to which some cases seem to me to point is one of a much stranger character. I think that there is evidence to show that many facts or pictures which have never even for a moment come within the apprehension of the supraliminal consciousness are nevertheless retained by the subliminal memory, and are occasionally presented in dreams with what seems a definite purpose. I quote an interesting case in Appendix IV. A.[47]
The same point, as we shall hereafter see, is illustrated by the phenomena of crystal-vision. Miss Goodrich-Freer,[48] for example, saw in the crystal the announcement of the death of a friend;—a piece of news which certainly had never been apprehended by her ordinary conscious self. On referring to the Times, it was found that an announcement of the death of some one of the same unusual name was contained in a sheet with which she had screened her face from the fire;—so that the words may have fallen within her range of vision, although they had not reached what we broadly call her waking mind.
This instance was of value from the strong probability that the news could never have been supraliminally known at all;—since it was too important to have been merely glanced at and forgotten.
In these cases the dream-self has presented a significant scene,—has chosen, so to say, from its gallery of photographs the special picture which the waking mind desired,—but has not needed to draw any more complex inference from the facts presumably at its disposal. I have now to deal with a small group of dreams which reason as well as remember;—if indeed in some of them there be not something more than mere reasoning on facts already in some way acquired,—something which overpasses the scheme prescribed for the present chapter.
In the first place we cannot doubt that definite data already known may sometimes be treated in somnambulism or ordinary dream with more than waking intelligence. Such are the cases of mathematical problems solved in somnambulism, or of the skeletal arrangement discovered by Agassiz in common sleep for scattered bones which had baffled his waking skill. I give in Appendix IV. B. the striking case of Professor Hilprecht where dream-intelligence is carried to its highest point. Professor Romaine Newbold (who records the case) is well versed in the analysis of evidence making for supernormal powers, and his explanation of the vision as the result of "processes of associative reasoning analogous to those of the upper consciousness" must, I think, be taken as correct. But had the incident occurred in a less critical age of the world,—in any generation, one may say, but this,—how majestic a proof would the phantasmal Babylonian's message be held to have afforded of his veritable co-operation with the modern savant in the reconstruction of his remote past!
I repeat that with this case of Professor Hilprecht's we seem to have reached the utmost intensity of sleep faculty within the limits of our ordinary spectrum. In almost every region of that spectrum we have found that the sleeper's faculty, under its narrow conditions, shows scattered signs of at least a potential equality with the faculty of waking hours.