In the last analysis the entire field of psychology may reduce to biological electrochemistry.

Unexpressed emotions will never die. They are buried alive and will come forth later in uglier ways.

We know less about the sexual life of little girls than of boys. But we need not feel ashamed of this distinction; after all, the sexual life of adult women is a 'dark continent' for psychology.

I cannot face with comfort the idea of life without work; work and the free play of the imagination are for me the same thing, I take no pleasure in anything else.

Even if all parts of a problem seem to fit together like the pieces of a jigsaw puzzle, one has to remember that the probable need not necessarily be the truth and the truth not always probable.

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

The very emphasis of the commandment: Thou shalt not kill, makes it certain that we are descended from an endlessly long chain of generations of murderers, whose love of murder was in their blood as it is perhaps also in ours.