The only phrase I have used by which I cannot absolutely stand is the expression "by a happy chance"; for I believe that the mental productions of each person are due not to uncaused chance, or to accident, but to trends of the social mind that have been set in motion by mental exigencies arising out of current events. As primitive peoples, however, have left no record of their mental sequences, we cannot say with confidence what were the exact experiences that led to the idea of using fire, or to any other device that transformed the relation of human beings to one another or to their material habitat. I only repeat that whatever caused the inventions caused all the remote effects of these, and that if the causes of the inventions were mental and spiritual, then an interpretation of history is not materialistic merely because it traces advancement to mechanical utilities. That I am right in tracing these to mental and spiritual causes is proved at least in the case of recent inventions. For we know that their causes were psychic; we know the mental atmosphere, and how it arose, that brought forth the telephone and aeroplane and submarine. We know that these were not due to physical necessities or to any material causes. They arose from the brooding of creative imaginations disciplined in a method learned by reflection upon former successes in discovery. We also know in what main particulars this modern atmosphere differs from that of former centuries. But such questions are not germane to my central theme, and so I pass them over lightly. Let me then return without further delay from this digression which has been made in the interests, not of my argument, but of my self-respect as a student of social facts. XXI. CONTACT OF PEOPLES Consider, for instance, that at the beginning of our century, for the first time in more than fifteen hundred years, the Christian nations came into contact with a mighty pagan power, and were compelled to acknowledge it as not only a political, but a moral, equal. Whoever knows the magical effect in the quickening of intellectual and spiritual life due to new contact with a contrasting type of national culture will agree that the meeting thus of Christendom with the so-called "heathen" world is a fact of prime significance in the history of man.