A consideration of the spread of Christianity in the first four centuries A.D. or of the spread of Islam in the seventh century will, we believe, support a reasonable hope that such a change in the minds of men, whatever else it may be, is a practicable change, that it can be done and that it may even probably be done. Consider our two instances. The propagandas of those two great religions changed and changed for ever the political and social outlook over vast areas of the world's surface. Yet while the stir for world unity begins now simultaneously in many countries and many groups of people, those two propagandas each radiated from a single centre and were in the first instance the teachings of single individuals; and while to-day we can deal with great reading populations and can reach them by press and printed matter, by a universal distribution of books, by great lecturing organizations and the like, those earlier great changes in human thought were achieved mainly by word of mouth and by crabbed manuscripts, painfully copied and passed slowly from hand to hand. So far it is only the trader who has made any effectual use of the vast facilities the modern world has produced for conveying a statement simultaneously to great numbers of people at a distance. The world of thought still hesitates to use the means of power that now exist for it. History and political philosophy in the modern world are like bashful dons at a dinner party; they crumble their bread and talk in undertones and clever allusions to their nearest neighbour, abashed at the thought of addressing the whole table. But in a world where Mars can reach out in a single night and smite a city a thousand miles away, we cannot suffer wisdom to hesitate in an inaudible gentility. The knowledge and vision that is good enough for the best of us is good enough for all. This gospel of human brotherhood and a common law and rule for all mankind, the attempt to meet this urgent necessity of a common control of human affairs, which indeed is no new religion but only an attempt to realize practically the common teaching of all the established religions of the world, has to speak with dominating voice everywhere between the poles and round about the world.