Abstract
Dreaming has fascinated mankind since antiquity. In most Christian cultures people believe that dreams bring messages of supernatural beings such as gods, angels and demons to the sleeper. Dreams contain often hidden messages, warning the sleeper for danger, predicting the future, clarifying situations, or rewarding or punishing the sleeping person. Many religious people assume that Gods preach through dreams. In contrast with sleep, where science reveals that sleep is crucial for physical health and many other functions, dreaming is still a mysterious process what difficult is to examine by science. There are several theories, but almost nobody can explain what a function of a dream is. The science of sleep starts toward the end of 1900 by a study of a certain Mary Cálkins, who found that in most dreams people told her, daily life is reflected. She formulated the ‘continuity’ hypothesis who later was shifted by Rosalind Cartwright in the direction of the role of dreams to the regulation of emotions. The continuity hypotheses was perfected by Calvin Hall and Robert Van de castle. Good old Freud looked deeper and formulated the ‘psychoanalytic’ theory implying that the psychoses of sick patients were perhaps coming from his adolescent period, which became a popular theory. It was in 1953 that Aserinsky and Kleitman discovered a second type of sleep, the REM sleep’ having many vivid dreams. Based on the brain activation by REM sleep Allan Hobson and Robert McCarley described the ‘activation-synthesis’ hypothesis. Next to the dreams of normal sleep and REM sleep, the third type of dreams appear n ‘hypnagogic hallucinations’. It is recently demonstrated that dreams in hypnagogic hallucinations can indeed have creative qualities.