If you must tell me your opinions, tell me what you believe in. I have plenty of doubts of my own.

Wisdom is only found in truth.

There is nothing in life so irrational, that good sense and chance may not set it to rights; nothing so rational, that folly and chance may not utterly confound it.

Against criticism a man can neither protest nor defend himself; he must act in spite of it, and then it will gradually yield to him.

People are always talking about originality; but what do they mean? As soon as we are born, the world begins to work upon us; and this goes on to the end. And after all, what can we call our own, except energy, strength, and will? If I could give an account of all that I owe to great predecessors and contemporaries, there would be but a small balance in my favor.

How can you come to know yourself? Never by thinking, always by doing. Try to do your duty, and you'll know right away what you amount to.

Should I not be proud, when for twenty years I have had to admit to myself that the great Newton and all the mathematicians and noble calculators along with him were involved in a decisive error with respect to the doctrine of color, and that I among millions was the only one who knew what was right in this great subject of nature?