There is no accomplishment so easy to acquire as politeness and none more profitable.

A book is like a child: it is easier to bring it into the world than to control it when it is launched there.

All progress depends upon the unreasonable person.

The mathematician is fascinated with the marvelous beauty of the forms he constructs, and in their beauty he finds everlasting truth.

Spend all you have before you die, and do not outlive yourself.

The only sensible person is my tailor. He measures me anew each time he sees me.

Every fool believes what his teachers tell him, and calls his credulity science or morality as confidently as his father called it divine revelation.