Health is the soul that animates all the enjoyments of life, which fade and are tasteless without it.

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.