The solution of the difficulties which formerly surrounded the mathematical infinite is probably the greatest achievement of which our age has to boast.

It will be said that the joy of mental adventure must be rare, that there are few who can appreciate it, and that ordinary education can take no account of so aristocratic a good. I do not believe this. The joy of mental adventure is far commoner in the young than in grown men and women. ...It is rare in later life because everything is done to kill it during education.

A priori Logical propositions are such as can be known a priori without study of the actual world.

Descartes, the father of modern philosophy ... would never-so he assures us-have been led to construct his philosophy if he had had only one teacher, for then he would have believed what he had been told; but, finding that his professors disagreed with each other, he was forced to conclude that no existing doctrine was certain.

I believe in using words, not fists. I believe in my outrage knowing people are living in boxes on the street. I believe in honesty. I believe in a good time. I believe in good food. I believe in sex.

Most of the greatest evils that man has inflicted upon man have come through people feeling quite certain about something which, in fact, was false.

What is new in our time is the increased power of the authorities to enforce their prejudices.