The great secret that all old people share is that you really haven't changed in seventy or eighty years. Your body changes, but you don't change at all. And that, of course, causes great confusion.

The past is a foreign country; they do things differently there.

Mathematics is the language with which God has written the universe.

The safest way to try and get what you want is to try and deserve what you want. It’s such a simple idea. It’s the golden rule so to speak. You want to deliver to the world what you would buy if you were on the other end.

What a man can be, he must be. This need we call self-actualization.

Understanding nature’s complexity is the ultimate challenge.