You can never solve a problem on the level on which it was created. Insanity: doing the same thing over and over again and expecting different results. A life lived for others is a life worthwhile.

The most evident difference springs from the important part which is played in man by a relatively strong power of imagination and by the capacity to think, aided as it is by language and other symbolically devices.

I never made one of my discoveries through the process of rational thinking

I'm more interested in the future than in the past, because the future is where I intend to live.

People are like bicycles. They can keep their balance only as long as they keep moving.

Don't let your brain interfere with your heart.

Man usually avoids attributing cleverness to somebody else unless it is an enemy.