The college fraternity or the college class, for instance, would be only a name, and presently not even that, if each of its members should withdraw. It is the members themselves, and not something outside of themselves. Yet to A, B, or C the fraternity or the class might as well be a river or a mountain by the side of which he stands, and which he is helpless to remove. He may modify it somewhat. He is surely modified by it somewhat; and the same is true of all the other groups in which A, B, or C belong. To a very considerable extent the question, Why does A, B, or C do so and so? is equivalent to the question, What are the peculiarities of the group to which A, B, or C belongs? It would never occur to A, B, or C to skulk from shadow to shadow of a night, with paint-pot and brush in hand, and to smear Arabic numerals of bill-poster size on sidewalk or buildings, if "class spirit" did not add stimulus to individual bent. Neither A, B, nor C would go out of his way to flatter and cajole a Freshman, if membership in a fraternity did not make a student something different from an individual. These are merely familiar cases which follow a universal law. In effect, the groups to which we belong might be as separate and independent of us as the streets and buildings of a city are from the population. If the inhabitants should migrate in a body, the streets and buildings would remain. This is not true of human groups, but their reaction upon the persons who compose them is no less real and evident. We are in large part what our social set, our church, our political party, our business and professional circles are. This has always been the case from the beginning of the world, and will always be the case. To understand what society is, either in its larger or its smaller parts, and why it is so, and how far it is possible to make it different, we must invariably explain groups on the one hand, no less than individuals on the other. There is a striking illustration in Chicago at present (summer, 1905). Within a short time a certain man has made a complete change in his group-relations. He was one of the most influential trade-union leaders in the city. He has now become the executive officer of an association of employers. In the elements that are not determined by his group-relationships he is the same man that he was before. Those are precisely the elements, however, that may be canceled out of the social problem. All the elements in his personal equation that give him a distinct meaning in the life of the city are given to him by his membership in the one group or the other. Till yesterday he gave all his strength to organizing labor against capital. Now he gives all his strength to the service of capital against labor.