The series of integers is obviously an invention of the human mind, a self-created tool which simplifies the ordering of certain sensory experiences.

Curiosity is its own reason.

It is only men who are free, who create the inventions and intellectual works which to us moderns make life worth while.

Since that deluge of newspaper articles I have been so flooded with questions, invitations, suggestions, that I keep dreaming I am roasting in Hell, and the mailman is the devil eternally yelling at me, showering me with more bundles of letters at my head because I have not answered the old ones.

It's not that I'm so smart, it's just that I stay with problems longer.

I have deep faith that the principle of the universe will be beautiful and simple

The Constitution only guarantees the American people the right to pursue happiness. You have to catch it yourself. A table, a chair, a bowl of fruit and a violin; what else does a man need to be happy?