The age of nomadic tribes of closely related individuals represents the maximum of physical differences. They were practically vast families, and there were as many groups as families. As the families came together to form cities the physical differences lessened, purity of blood was replaced by the requirement of domicile, and all who lived within the city bounds became gradually to be regarded as members of the group; _i. e._, there was a slight and slow breaking down of physical barriers. This, however, was accompanied by an increase of the spiritual and social differences between cities. This city became husbandmen, this, merchants, another warriors, and so on. The _ideals of life_ for which the different cities struggled were different. When at last cities began to coalesce into nations there was another breaking down of barriers which separated groups of men. The larger and broader differences of color, hair and physical proportions were not by any means ignored, but myriads of minor differences disappeared, and the sociological and historical races of men began to approximate the present division of races as indicated by physical researches. At the same time the spiritual and physical differences of race groups which constituted the nations became deep and decisive. The English nation stood for constitutional liberty and commercial freedom; the German nation for science and philosophy; the Romance nations stood for literature and art, and the other race groups are striving, each in its own way, to develope for civilization its particular message, its particular ideal, which shall help to guide the world nearer and nearer that perfection of human life for which we all long, that "one far off Divine event."