The erotic instinct is something questionable, and will always be so whatever a future set of laws may have to say on the matter. It belongs, on the one hand, to the original animal nature of man, which will exist as long as man has an animal body. On the other hand, it is connected with the highest forms of the spirit. But it blooms only when the spirit and instinct are in true harmony. If one or the other aspect is missing, then an injury occurs, or at least there is a one-sided lack of balance which easily slips into the pathological. Too much of the animal disfigures the civilized human being, too much culture makes a sick animal.

The Psychology of the Unconscious (1943)