Peace cannot be kept by force. It can only be achieved by understanding. You cannot subjugate a nation forcibly unless you wipe out every man, woman, and child. Unless you wish to use such drastic measures, you must find a way of settling your disputes without resort to arms.

When forced to summarize the general theory of relativity in one sentence: Time and space and gravitation have no separate existence from matter.

The daily struggle does not arise from a purpose or a program, but from an immediate need.

So would a Being, endowed with higher insight and more perfect intelligence, watching man and his doings, smile about man's illusion that he was acting according to his own free will.

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

The supreme goal of all theory is to make the irreducible basic elements as simple and as few as possible without having to surrender the adequate representation of a simple datum of experience.

Earth is the insane asylum of the universe.