Dreams are defined as the mental activity of the sleeper. These are the result of a disturbance of sleep. We would not have had a dream unless something disturbing had happened during our sleep, and the dream is the reaction to that disturbance. The content of a dream is more or less determined by the individual personality of the dreamer, by his age, sex, class, standard of education and habitual way of living, and by the events and experiences of his previous life. We dream most frequently of the things on which our warmest passions are centered. This shows that our passions have an influence on the production of our dreams. The ambitious man dreams of the laurels he has won, or of those, he has still to win; while the lover is busy in his dreams with the object of his sweet hopes.
When we wish to go to sleep, we close our most important sensory channels, our eyes, and try to protect the other senses from all stimuli. We cannot keep stimuli completely away from our sense organs. The sensory stimuli that reach us during sleep may very well become sources of dream. There are a great number of such stimuli, ranging from the unavoidable ones to the accidental, which may put an end to sleep. A bright light may force its way into our eyes, a noise may make itself heard, or some strong-smelling substance may stimulate our nose. Attentive observers have collected a whole series of dreams in which there has been such a far-reaching correspondence between a stimulus noticed on waking and the content of the dream. A peal of thunder will set us in the midst of a battle; a crowing of a cock may turn into a man’s cry of terror. If our head happens to get under the pillow, we dream of being beneath a huge overhanging rock, which is on the point of burying us under its weight.
We must bear in our mind that almost all our internal organs become a source of sensations when they are in the state of excitation during illness. During sleep, the mind attains a far deeper and wider sensory consciousness of somatic events than during the waking state. Instances of the diagnostic power of dreams are discovered in times that are more recent. Thus the story of a 43-year-old woman is worth noticing who while apparently in perfect health, was for some years tormented by anxiety dreams. She was then medically examined and found to be in early stages of an affection of the heart, to which she eventually succumbed. Dreams are phenomena, which occur in healthy people, and it is obvious that organic illness can be counted among its indispensable conditions.
When we are dealing with the relations of the dreams to waking life and with the material of dreams, we find that men dream of what they do during the daytime, and of what interests them while they are awake. Such an interest, carried over from waking life into sleep will be a link between dreams and life. Dream images are probably illusions, since they arise from faint sense impressions, which never cease during sleep. Dreams are not meaningless and absurd. They are fulfillment of wishes, result of intelligible waking mental act and are constructed by a highly complicated activity of the mind.