I would never die for my beliefs because I might be wrong.
Almost everything that distinguishes the modern world from earlier centuries is attributable to science, which achieved its most spectacular triumphs in the seventeenth century.
Revolution as an ideal concept always preserves the essential content of the original thought: sudden and lasting betterment.
Boredom is… a vital problem for the moralist, since half the sins of mankind are caused by the fear of it.
Play is a uniquely adaptive act, not subordinate to some other adaptive act, but with a special function of its own in human experience.
The coward wretch whose hand and heart Can bear to torture aught below, Is ever first to quail and start From the slightest pain or equal foe.
Fear is the main source of superstition, and one of the main sources of cruelty. To conquer fear is the beginning of wisdom.
Ethics is in origin the art of recommending to others the sacrifices required for cooperation with oneself.
The true spirit of delight, the exaltation, the sense of being more than Man, which is the touchstone of the highest excellence, is to be found in mathematics as surely as poetry.
Many people would sooner die than think; in fact, they do so.