It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt.

A smart man makes a mistake, learns from it, and never makes that mistake again. But a wise man finds a smart man and learns from him how to avoid the mistake altogether.

Smartness runs in my family. When I went to school I was so smart my teacher was in my class for five years.

I believe alien life is quite common in the universe, although intelligent life is less so. Some say it has yet to appear on planet earth.

There are no great limits to growth because there are no limits of human intelligence, imagination, and wonder.