An investment in knowledge pays the best interest.

I am so clever that sometimes I don't understand a single word of what I am saying.

There is no authority who decides what is a good idea.

The first principle is that you must not fool yourself and you are the easiest person to fool.

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

Investigate, educate and organize.

The ability to observe without evaluating is the highest form of intelligence.

I do not know how to teach philosophy without becoming a disturber of the peace.

Books are for people who wish they were somewhere else.

Any man who reads too much and uses his own brain too little falls into lazy habits of thinking.

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

The only good is knowledge and the only evil is ignorance.

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

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

There is nothing more notable in Socrates than that he found time, when he was an old man, to learn music and dancing, and thought it time well spent.

Education is a system of imposed ignorance.

I am a part of everything that I have read.

Real learning comes about when the competitive spirit has ceased.

The progressive development of man is vitally dependent on invention.

Liberty without Learning is always in peril and Learning without Liberty is always in vain.

Medicine is my lawful wife and literature my mistress; when I get tired of one, I spend the night with the other.