The most beautiful experience in the world is the experience of the mysterious.

I believe my theory of relativity to be true. But it will only be proved for certain in 1981, when I am dead.

A man's ethical behaviour 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.

It has become appallingly obvious that our technology has exceeded our humanity.

My pacifism is not based on any intellectual theory but on a deep antipathy to every form of cruelty and hatred.

Today we must abandon competition and secure cooperation. This must be the central fact in all our considerations of international affairs; otherwise we face certain disaster. Past thinking and methods did not prevent world wars. Future thinking must prevent wars...The stakes are immense, the task colossal the time is short. But we may hope- we must hope- that man's own creation, man's own genius, will not destroy him.

Concepts that have proven useful in ordering things easily achieve such authority over us that we forget their earthly origins and accept them as unalterable givens.