Most people confuse “self-knowledge” with knowledge of their conscious ego-personalities. Anyone who has any ego-consciousness at all takes it for granted that he knows himself. But the ego knows only its own contents, not the unconscious and its contents. People measure their self-knowledge by what the average person in their social environment knows of himself, but not by the real psychic facts which are for the most part hidden from them. In this respect the psyche behaves like the body, of whose physiological and anatomical structure the average person knows very little too. Although he lives in it and with it, most of it is totally unknown to the layman, and special scientific knowledge is needed to acquaint consciousness with what is known of the body, not to speak of all that is not known, which also exists.
— C. G. Jung, “The Plight of the Individual in Modern Society” (1957)