Looked at in itself, so far as we can isolate it from its surroundings, man's nature is distinguished from that of lower animals by two features, both of them essentially social and tending to unity. He is more deeply and permanently attached to members of his own species, by affection, sympathy, veneration, tradition, than any other creature. And he is a reasoning being, reason itself requiring the contact and agreement of various minds. The incomparably greater force which he has acquired in the world, over all other species and over nature itself, is due to the working of these two factors. At starting he was physically less strong than many other creatures, and if he fought with others of his own kind, other animal species did the same. He was ahead of them by his reason, and reason acted, and must act, through the concert of thinking beings. This concert is not merely, or even mainly, an attachment among those living at the same time to co-operate for some common end; it is with man a conscious sequence of one generation on another. Sometimes the movement of adaptation is slower, sometimes quicker, but in every case the living are carrying on the work of the dead, and their co-operation in time as well as space is due to the working of the same qualities of attachment and reason, the social factors, by which at any moment a community of men is bound together. Still looking at the matter _a priori_, it is clear that the vast community of mankind, though it has come more closely in contact in recent years over all the planet, yet acts, and must act, habitually and momentarily, through many smaller aggregates. Of these the leading types are the family and the country or nation. The former is not directly relevant to our inquiry, the latter plays a leading part in it. The former is less dependent on external conditions of land-formation and the like, and is in consequence more universal, more purely human. The latter has been shaped by geographical conditions, by racial qualities, by the apparent accidents of history. Its relation to the larger units of human society raises the most difficult, fundamental and unavoidable questions. To curb aggressive nationalism is the root-problem of the present war. To reconcile permanently nationalism with humanity would be to establish the everlasting peace.