But there is another way in which common sense can be brought to the criticism of some prodigious racial theories. To employ the same figure, suppose the scientific historians explain the historic centuries in terms of a prehistoric division between short-sighted and long-sighted men. They could cite their instances and illustrations. They would certainly explain the curiosity of language I mentioned first, as showing that the short-sighted were the conquered race, and their name therefore a term of contempt. They could give us very graphic pictures of the rude tribal war. They could show how the long-sighted people were always cut to pieces in hand-to-hand struggles with axe and knife; until, with the invention of bows and arrows, the advantage veered to the long-sighted, and their enemies were shot down in droves. I could easily write a ruthless romance about it, and still more easily a ruthless anthropological theory. According to that thesis which refers all moral to material changes, they could explain the tradition that old people grow conservative in politics by the well-known fact that old people grow more long-sighted. But I think there might be one thing about this theory which would stump us, and might even, if it be possible, stump them. Suppose it were pointed out that through all the three thousand years of recorded history, abounding in literature of every conceivable kind, there was not so much as a mention of the oculist question for which all had been dared and done. Suppose not one of the living or dead languages of mankind had so much as a word for "long-sighted" or "short-sighted." Suppose, in short, the question that had torn the whole world in two was never even asked at all, until some spectacle-maker suggested it somewhere about 1750. In that case I think we should find it hard to believe that this physical difference had really played so fundamental a part in human history. And that is exactly the case with the physical difference between the Celts, the Teutons and the Latins.