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 an important part in the world's history, though you may hear less about them. Moral courage is more rare than physical courage. To display physical courage may make a man a popular hero. If he fails he is stamped as a coward. To display moral courage more often than not makes a man unpopular. There is no audience to applaud and it is quite easy to be a moral coward without any one, even intimate friends, finding it out. It is far simpler to say "Yes" when every one else is saying "Yes." He who rows against the stream cannot hope to carry many with him, and his progress must be slow.

Nothing can have upset men's calculations more than the first great discoveries of astronomy. No doubt people scoffed when Pythagoras told them the earth was round and not flat, as they supposed. But it was a still more disturbing idea to be told that the earth was not the center of the universe, with the sun and moon and stars revolving round it. Most men firmly believed this to be the case up to the fifteenth century. And when Copernicus first elaborated in a book, between 1506 and 1512, the heliocentric theory, that is to say the theory that the sun was the center round which the earth and the other planets revolved, it was a long time before any one would treat such an idea seriously. We may laugh at the ignorance of our forefathers, and we may declare glibly that of course the earth goes round the sun, but there are not many of us who would be ready to