Man must not check his reason by tradition, but, contrariwise, must check tradition by reason.

If you no longer believe in the God in whom you believed in before, this comes from the fact that there was something wrong with your belief, and you must strive to understand better that which you call God.

There is no significant idea which cannot be explained to an intelligent twelve year old boy in fifteen minutes.

Do not be sad about what you do not have. Instead, be happy about what you do have. If you will be sad about what you don't have, you will not be happy about what you do have.

Everything I know, I know because of love.

Happiness is pleasure without regret

The example of a syllogism that he had studied in Kiesewetter's logic: Caius is a man, men are mortal, therefore Caius is mortal, had throughout his whole life seemed to him right only in relation to Caius, but not to him at all.