I have remarked very clearly that I am often of one opinion when I am lying down and of another when I am standing up.

What is the good of drawing conclusions from experience? I don't deny we sometimes draw the right conclusions, but don't we just as often draw the wrong ones?

Above all things expand the frontiers of science: without this the rest counts for nothing.

Much can be inferred about a man from his mistress: in her one beholds his weaknesses and his dreams.

We cannot remember too often that when we observe nature, and especially the ordering of nature, it is always ourselves alone we are observing.

Honest unaffected distrust of human abilities under all circumstances is the surest sign of strength of mind.

If all mankind were suddenly to practice honesty, many thousands of people would be sure to starve.