ABSTRACT
MANY philosophers and psychologists who have thought about the nature of dreams, have believed that a dream is both a form of mental activity and a conscious experience. Descartes held that a human mind must be conscious at all times, this notion resulting from his supposed demonstration that the ‘essence’ or ‘principal attribute’ of mental substance is consciousness, and that so long as a mind exists there must exist ‘modes’ of that essence, i.e. states of consciousness, mental occurrences and mental acts. He says in a letter:
