Knowledge exists in two forms - lifeless, stored in books, and alive, in the consciousness of men. The second form of existence is after all the essential one; the first, indispensable as it may be, occupies only an inferior position.

One always likes to do the things for which one has ability.

The physicist's greatest tool is his wastebasket.

Human beings, in their thinking, feeling and acting are not free agents but are as causally bound as the stars in their motion.

God does not play dice.

Science will stagnate if it is made to serve practical goals.

Figuring out how to think about the problem.