But it is not conquest alone that has operated to promote association, and, by liberating mental power from the necessities of warfare, to promote civilization. If the diversities of climate, soil, and configuration of the earth's surface operate at first to separate mankind, they also operate to encourage exchange. And commerce, which is in itself a form of association or co-operation, operates to promote civilization, not only directly, but by building up interests which are opposed to warfare, and dispelling the ignorance which is the fertile mother of prejudices and animosities. And so of religion. Though the forms it has assumed and the animosities it has aroused have often sundered men and produced warfare, yet it has at other times been the means of promoting association. A common worship has often, as among the Greeks, mitigated war and furnished the basis of union, while it is from the triumph of Christianity over the barbarians of Europe that modern civilization springs. Had not the Christian Church existed when the Roman Empire went to pieces, Europe, destitute of any bond of association, might have fallen to a condition not much above that of the North American Indians or only received civilization with an Asiatic impress from the conquering scimiters of the invading hordes which had been welded into a mighty power by a religion which, springing up in the deserts of Arabia, had united tribes separated from time immemorial, and, thence issuing, brought into the association of a common faith a great part of the human race. Looking over what we know of the history of the world, we thus see civilization everywhere springing up where men are brought into association, and everywhere disappearing as this association is broken up. Thus the Roman civilization, spread over Europe by the conquests which insured internal peace, was overwhelmed by the incursions of the northern nations that broke society again into disconnected fragments; and the progress that now goes on in our modern civilization began as the feudal system again began to associate men in larger communities, and the spiritual supremacy of Rome to bring these communities into a common relation, as her legions had done before. As the feudal bonds grew into national autonomies, and Christianity worked the amelioration of manners, brought forth the knowledge that during the dark days she had hidden, bound the threads of peaceful union in her all-pervading organization, and taught association in her religious orders, a greater progress became possible, which, as men have been brought into closer and closer association and co-operation, has gone on with greater and greater force.