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.

It is a mania shared by philosophers of all ages to deny what exists and to explain what does not exist.

We shall see but a little way if we require to understand what we see.