Only the real, rare, true scientific minds can endure doubt, which is attached to all our knowledge.

[The child receives impressions like] a photographic exposure that can be developed after any interval of time and transformed into a picture.

The price of civilization is instinctual renunciation.

A transference neurosis corresponds to a conflict between ego and id, a narcissistic neurosis corresponds to that between between ego and super-ego, and a psychosis to that between ego and outer world.

Conscience is the internal perception of the rejection of a particular wish operating within us.

The conscious mind may be compared to a fountain playing in the sun and falling back into the great subterranean pool of subconscious from which it rises.

My boy! Smoking is one of the greatest and cheapest enjoyments in life, and if you decide in advance not to smoke, i can only feel sorry for you.