With the fearful strain that is on me night and day, if I did not laugh I should die.

I know that I am intelligent, because I know that I know nothing.

I decided to sell my drawings. However, I didn't want people to buy my drawings because the professor of physics isn't supposed to be able to draw - isn't that wonderful - so I made up a false name.

Those who educate children well are more to be honored than they who produce them; for these only gave them life, those the art of living well.

Nearly every man who develops an idea works it up to the point where it looks impossible, and then he gets discouraged. That's not the place to become discouraged.