William James describes a man who got the experience from laughing-gas; whenever he was under its influence, he knew the secret of the universe, but when he came to, he had forgotten it. At last, with immense effort, he wrote down the secret before the vision had faded. When completely recovered, he rushed to see what he had written. It was 'A smell of petroleum prevails throughout'.

To be able to concentrate for a considerable time is essential to difficult achievement.

Measures of sterilization should, in my opinion, be very definitely confined to persons who are mentally defective

If a man is offered a fact which goes against his instincts, he will scrutinize it closely, and unless the evidence is overwhelming, he will refuse to believe it. If, on the other hand, he is offered something which affords a reason for acting in accordance to his instincts, he will accept it even on the slightest evidence. The origin of myths is explained in this way.

Remember your humanity, and forget the rest.

I never held Negroes to be inherently inferior. The statement in Marriage and Morals refers to environmental conditioning. I have had it withdrawn from subsequent editions because it is clearly ambiguous.

Do not use power to suppress opinions you think pernicious, for if you do the opinions will suppress you.