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.

The primitive stages can always be re-established; the primitive mind is, in the fullest meaning of the word, imperishable.

It would be one of the greatest triumphs of humanity, one of the most tangible liberations from the constraints of nature to which mankind is subject, if we could succeed in raising the responsible act of procreating children to the level of a deliberate and intentional activity and in freeing it from its entanglement with the necessary satisfaction of a natural need.

It is impossible to overlook the extent to which civilization is built upon a renunciation of instinct.

Religion [is] the universal obsessional neurosis of humanity

Do you not know how uncontrolled and unreliable the average human being is in all that concerns sexual life?

But one thing about human beings puzzles me the most is their conscious effort to be connected with the object of their affection even if it kills them slowly within.