Real sign of intelligence isn't knoweldge, it's imagination

The mere formulation of a problem is far more essential than its solution, which may be merely a matter of mathematical or experimental skills. To raise new questions, new possibilities, to regard old problems from a new angle requires creative imagination and marks real advances in science.

The most important method of education always has consisted of that in which the pupil was urged to actual performance.

This is what the painter, the poet, the speculative philosopher, and the natural scientists do, each in his own fashion.

If you can't explain what you are doing to a nine-year-old, then either you still don't understand it very well, or it's not all that worthwile in the first place.

This is too difficult for a mathematician. It takes a philosopher. The hardest thing in the world to understand is the income tax.

Nothing truly valuable arises from ambition or from a mere sense of duty; it stems rather from love and devotion towards men and towards objective things.