“If at first the idea is not absurd, then there is no hope for it.”

“For an idea that does not first seem insane, there is no hope.”

“Only those who attempt the absurd can achieve the impossible.”

“Pure mathematics is in its way the poetry of logical ideas.”

“It seems to me that the idea of a personal God is an anthropological concept which I cannot take seriously. I also cannot imagine some will or goal outside the human sphere... Science has been charged with undermining morality, but the charge is unjust. A man's ethical behavior should be based effectually on sympathy, education, and social ties and needs; no religious basis is necessary. Man would indeed be in a poor way if he had to be restrained by fear of punishment and hope of reward after death.”

“The only sure way to avoid making mistakes is to have no new ideas.”

“The idea of a personal God is quite alien to me and seems even naïve.”