Abstract
1. Although the nightmare is a common form of dream, and beyond doubt an authentic experience, it has never been adequately explained and in fact still remains to be properly defined.
2. We have attempted here to arrive at some definition of nightmare, and in so doing to sketch a tentative classification of dreams. Examples have been taken from the dreams of patients under treatment, and from the dream-like creations of Edgar Allan Poe.
3. Four types of dreams are briefly described:
a. The wish-fulfilling dream, which is the type best known and understood.
b. The pipe-dream, an extreme form of wish-fulfilling dream, with certain specific features.
c. The nightmare, characterized by chaotic structure and highly disturbing emotions (dread, horror, loathing, disgust) and not adequately explained by any known hypothesis.
d. The intuitive dream, in which we find unconscious and apparently instinctive perceptions of truth which are only later available to conscious reasoning.
4. An attempt is made to show in which way these types of dream are distinct from one another, and in which way they are inter-related.
5. Finally, elements common to both the phenomena of nightmare and those of functional psychoses are pointed out, with the suggestion that similar causative mechanisms may be at work in both.