As for my memory, I have a particularly good one. I never keep any record of my investigations or experiments. My memory files all these things away conveniently and reliably. I should say, though, that I didn’t cumber it up with a lot of useless matter.

Mathematics is the most exact science, and its conclusions are capable of absolute proof. But this is so only because mathematics does not attempt to draw absolute conclusions. All mathematical truths are relative, conditional. In E. T. Bell Men of Mathematics, New York: Simona and Schuster, 1937.

Money is a stupid measure of achievement, but unfortunately it is the only universal measure we have.

Spiritual power is a force which history clearly teaches has been the greatest force in the development of men. Ye. we have been merely playing with it and never have really studied it as we have the physical forces. Some day people will learn that material things do not bring happiness, and are of little use in making people creative and powerful. Then the scientists of the world will turn their laboratories over to the study of spiritual forces which have hardly been scratched.

Take the rose—most people think it very beautiful: I don’t care for It at all. I prefer the cactus, for the simple reason that it has a more interesting personality. It has wonderfully adapted itself to its surroundings! It is the best illustration of the theory of evolution in plant life.

No man really becomes a fool until he stops asking questions.

I have succeeded in getting my actual work down to thirty minutes a day. That leaves me eighteen hours for engineering.