I believe there is no source of deception in the investigation of nature which can compare with a fixed belief that certain kinds of phenomena are IMPOSSIBLE.

The good or bad is not in the circumstance, but only in the mind...that encounters it.

The world is all the richer for having a devil in it, so long as we keep our foot upon his neck.

Each of us literally chooses, by his way of attending to things, what sort of universe he shall appear to himself to inhabit.

Philosophy is at once the most sublime and the most trivial of human pursuits.

If you wish to upset the law that all crows are black, you mustn't seek to show that no crows are; it is enough if you prove one single crow to be white.

The minute a man ceases to grow, no matter what his years, that minute he begins to be old.