The Interpretation of Dreams by Sigmund Freud Chapter 3 Page 29

— indeed, that in certain cases community of symbol is greater than community of speech. Since the dreamers do not themselves know the meaning of the symbols they use, it remains a puzzle whence arises their relationship with what they replace and denote.

The fact itself is undoubted, and becomes of importance for the technique of the interpretation of dreams, since by the aid of a knowledge of this symbolism it is possible to understand the meaning of the elements of a dream, or parts of a dream, occasionally even the whole dream itself, without having to question the dreamer as to his own ideas. We thus come near to the popular idea of an interpretation of dreams, and, on the other hand, possess again the technique of the ancients, among whom the interpretation of dreams was identical with their explanation through symbolism.