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

Learning never exhausts the mind.

There is one quality which one must possess to win, and that is definiteness of purpose, the knowledge of what one wants, and a burning desire to possess it.

All knowledge that the world has ever received comes from the mind; the infinite library of the universe is in our own mind.

The task of a writer is not to solve the problem but to state the problem correctly.

Knowledge becomes evil if the aim be not virtuous.

Learn as though you would never be able to master it; hold it as though you would be in fear of losing it.

Intelligence plus character-that is the goal of true education.

Imagination is more important than knowledge.

Dare to think for yourself.

The most savage controversies are those about matters as to which there is no good evidence either way.

Integrity without knowledge is weak and useless, and knowledge without integrity is dangerous and dreadful.

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

I am a part of everything that I have read.

No power and no treasure can outweigh the extension of our knowledge.

Any knowledge that doesn't lead to new questions quickly dies out: it fails to maintain the temperature required for sustaining life.

The deepest sin against the human mind is to believe things without evidence.

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

Books! I dunno if I ever told you this, but books are the greatest gift one person can give another.

To every action there is always an equal and opposite or contrary, reaction

What we know is a drop, what we don't know is an ocean.