The third law, that of Contrast, applies to the ethnic mind the curious fact in mental life that a prolonged devotion to one idea leads to a reaction in which the opposite of that idea becomes dominant. This is even more conspicuous in the history of progressive nations than in that of individuals. Upon this depends that periodicity in the lives of peoples which has so often been remarked by historians. The above mentioned facts and laws demonstrate that there is a true unity of existence in the ethnic mind; that it has its own traits, forms, and processes of growth and decay, quite apart from those of the individual mind; that it is not to be studied by the methods of experimental psychology, but by methods drawn from the observation of its own modes of being; and that it is this abstraction, if you please, which is the prime factor in the fate of the group over which it rules. But I must return again to the definition of the Group. It must not be said that I leave any obscurity in the connotation of that prominent word. There may be—there always are—many forms of groups in the same community, and these by no means cover each other coterminously. Take many an American village, for example. There are the religious groups, Protestant and Catholic; the political parties, Republicans and Democrats, not at all of the same individuals as the former; and there may be the linguistic groups, German and American, different again from both the former; and the racial groups, whites and negroes. Something similar to this is found on a large scale in every people, every nation; and the serious problem presents itself,—how are we, from these heterogeneous elements, to reach anything which we can properly call the common sentiment, the general mind of the mass? The example I have chosen of the American village is an extreme one. In a primitive, isolated tribe of Indians, in a remote mountain village, or a rarely visited island, the task would be vastly easier. But the principle in all cases is the same. By eliminating particular after particular, as the logicians say, we finally reach a general, a consensus of opinion and aspiration on a variety of topics, with which the full number required by the mathematical method already stated will agree. These common sentiments will represent the active influence of that community, and very accurately measure its value in development. Being an American village, we can without doubt predict that it will be of one mind that making money should be the chief aim of active exertion; that respect for the law of the land should be cultivated; and that performing recognised duties to one’s family should be taught as indispensable.