If you want the present to be different from the past, study the past.

Necessity is the mother of invention.

Science is not only a disciple of reason but, also, one of romance and passion.

I decided to teach because I think that any person who studies philosophy has to be involved actively.

He who would learn to fly one day must first learn to stand and walk and run and climb and dance; one cannot fly into flying.

A cynic is a man who knows the price of everything, and the value of nothing.

Although modesty is natural to man, it is not natural to children. Modesty only begins with the knowledge of evil.

To educate a person in the mind but not in morals is to educate a menace to society.

What is freedom of expression? Without the freedom to offend, it ceases to exist.

Science is what we have learned about how to keep from fooling ourselves.

All stable processes we shall predict. All unstable processes we shall control.

It is what you read when you don't have to that determines what you will be when you can't help it.

Learning never exhausts the mind.

God created man in His own image, says the Bible; philosophers reverse the process: they create God in theirs.

Never help a child with a task at which he feels he can succeed.

Language is courage: the ability to conceive a thought, to speak it, and by doing so to make it true.

Courage, conviction and confidence.

The fullness of knowledge only comes through the awareness of ignorance.

An investment in knowledge pays the best interest.

If I could explain it to the average person, I wouldn't have been worth the Nobel Prize.

Books are as useful to a stupid person as a mirror is useful to a blind person.