1 See Chapter VII, "Symbolism in Dreams".

The Freudian theory of dream construction may be true and may be required to explain certain aspects of the dream life of those who are mentally disordered, but I find it very difficult to trace its connection with a dream life that is so profoundly different, or with the working of a dream mind which carries on its activities in close and harmonious co-operation with the normal life of the mind by day.

It is natural that a large proportion of the literature concerning sleep and dreams should be written from the point of view of medical science. The growth of the belief in the therapeutic value of the study of the unconscious has brought this about.

Apart from the numerous school of writers who follow more or less on the lines of Freudian psychoanalysis, the clinical study of dreams has been pursued zealously in France and in America, as well as in this country; and the unprofessional student can only look with respect and some natural awe at the vast library of books that contain the result of these investigations.

Amongst a rarer class of books, those concerned with problems of normal dreaming, with the dreams of sane and healthy persons, Mr. Havelock Ellis's "World of Dreams" seems one of the wisest and most lucid. It is, he says, "by learning to observe and to understand the ordinary nightly experience of dream life that we shall best be laying the foundation of future superstructures. For, rightly understood, dreams may furnish us with clues to the whole of life."1

The plea that this study should not be confined to medical science, and that others besides physicians should investigate it from a different standpoint from theirs, is beginning to have a response; and philosophers are occupied to-day with the problem of dreams. M. Bergson, in a lecture delivered originally before the Institut Psychologique, and now republished in England, has given us his explanation of the source from which they spring. He does not dwell upon the Freudian theories of repressed desires and symbolic meanings; but he gives us his explanation of dream consciousness and of the method by which he believes that dreams originate. Sensations of sudden light, sensations of sound and of feeling, "which are presented to our eyes, to our ears, to our touch during sleep as well as during waking," make, he tells us, the starting-point of dreams, for our senses remain active, and our faculty of sense impression does not stop whilst we are asleep, although the impressions that are conveyed to our mind are confused and vague. These impressions are, he says, the "raw material out of which memory weaves the web of our dreams." A dream may, for instance, have for its starting-point the sensation caused by a light falling on the face of the sleeper.

In the dream this may be converted into the gleam of moonlight on a pool, into a woman's white dress, or the shining of fire; and similarly a sound which strikes upon the ear whilst we sleep may turn into the thunder of cannon, the roar of a train or the crash of waves breaking on a cliff. The dream imagination has seized upon the sense impression and interpreted it as it pleased, and the dream is forthwith started on its course. The vague indistinct impression that the dreamer received from his eyes, his ears, or sense of touch are caught and are converted into precise and determined objects by his imagination.

1 Havelock Ellis, "The World of Dreams".

In this explanation of the starting-point of dreams in sense impressions, M. Bergson follows closely in the steps of other writers, and especially in those of M. Maury, a French writer who wrote on dreams some forty years ago. M. Maury's theory does not in point of fact carry us very far towards a complete understanding of the problems connected with the working of the mind in sleep. Some dreams certainly have their origin in perturbations of the brain caused by vibrations started from outside the body and striking on the senses; whilst others are started by vibrations proceeding from within the body and communicated by the nerve system to the brain. But it is clear that neither of these statements gives more than a small part of the truth concerning the origin of dreams. They may, indeed, be started by vibrations, just as a thought may be started in that way, but dreams are without doubt also set in motion by the mechanism of the mind and of its faculty memory - just as our thoughts are; and our dreams, like our thoughts, are shaped by the operation of the mind.

Dreams that have their origin in a physical impression are defined by some writers as sensorial dreams, and those that originate mainly in mental impressions and memories as psychic dreams; but this classification needs considerable qualification. It is, of course, no easy matter to trace back a dream to the sense impression which may have started it; because, as such impressions necessarily occur whilst we are asleep, no proof of them is generally available beyond the dream itself.1 I am convinced that the greater number of my own dreams, especially the long coherent dreams, which are the dreams of my deepest sleep, would come under the heading of psychic dreams; for they evidently have their origin in some strong mental impression, and I find that I am hardly ever aware of the sense impressions which have possibly helped to stimulate them. The mental impressions which start a dream on its course are generally easily recognised, and are in many instances created by emotions or thoughts that have preoccupied the mind during the day. When, however, it happens that the thoughts of our waking hours are thus carried on into our sleep, M. Bergson would have us believe that we are only imperfectly asleep - hardly, he thinks, asleep at all.

To use his own words in defining his theory of "disinterestedness": To sleep is to become disinterested; one sleeps to the exact extent to which one "becomes disinterested" And again he says: "At a given moment, I become disinterested in the present situation, in the present action - in short, in all which previously has fixed and guided my memory; in other words, I am asleep.