A theory can be proved by experiment; but no path leads from experiment to the birth of a theory.

Condemnation without investigation is the height of ignorance

Capitalism has brought with it progress, not merely in production but also in knowledge.

Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.

All religions, arts and sciences are branches of the same tree. All these aspirations are directed toward ennobling man's life, lifting it from the sphere of mere physical existence and leading the individual towards freedom.

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

Everybody acts not only under external compulsion but also in accordance with inner necessity.