Part 1 of Essay
Dreaming is a form of mental activity that occurs during sleep. The nature of dream activities has been characterized by many clinical and laboratory studies. These studies are more perceptual than conceptual: things are seen and heard rather than being subject to thought. Visual perception is present in almost all dream ....

Part 2 of Essay
.... is that the latter tends to be an internal hallucinatory-like experience disconnected from the external world. Many dreams collected in laboratories are rather common, but some people tend to experience some bizarre dreams. Early in the 20th century, Sigmund Freud believed that dream content was composed of the mental processes different from that used in the awake state. He believed this was what dominated the dreaming mind. He described this "process" as characterized by more primitive mechanisms, by ....