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

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

Dare to think for yourself.

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

A child educated only at school is an uneducated child.

An investment in knowledge pays the best interest.

Necessity is the mother of invention.

As we acquire more knowledge, things do not become more comprehensible but more mysterious.

It is possible to fly without motors, but not without knowledge and skill.

That men do not learn very much from the lessons of history is the most important of all the lessons that history has to teach.

With educated people, I suppose, punctuation is a matter of rule; with me it is a matter of feeling. But I must say I have great respect for the semi-colon; it's a useful little chap.

In order to stave off covetouness, greed, and spite, citizens world over must be educated.

Courage, conviction and confidence.

Just when I thought there wasn't room enough for another thought in my head, I had this great idea.

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

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

If you can't explain it simply, you don't understand it well enough.

The knowledge of all things is possible

Opinion is the medium between knowledge and ignorance.

Reading is to the mind what exercise is to the body.

I cannot live without books.