78 THE AMERICAN JOURNAL OF SOCIOLOGY
stations; on the contrary, these only multiply in the way best suited to facilitate the traffic for short distances, between neigh- boring groups, as well as for the great distances between the limits of the globe. The very fact of the existence of frontiers, not only geographical, but social, is a factor in the development of civilization; the more they multiply, the more they indicate that social organization is in progress. As might be expected, the differentiation is accompanied by a corresponding co-ordi- nation. It is with frontiers as with races and types: the more numerous they are, the more the differences disappear, and the better the fusion realized through the disappearance of extreme forms. In a word, the multiplication of limits adequate to the progress of the organization is in the same class as that of races, a perfecting of the adaptation of the species. It is an element of order, of peace, of progress; the result of it is the establishment of a new average, and at the same time the strongest possible indi- vidualization of special groups and of their units an individu- alization impossible in homogeneous, small, or widely scattered societies. This is especially true when there is added a certain equality of the forces between a society and the neighboring societies. This equality, or rather equivalence, is favorable to an exterior equilibrium, to peaceful relations with the outside world, to the formation of agreements, of treaties, and of federa- tions; in a word favorable to the lessening of the historic and gross role of frontiers as obstacles. This equality may end in the complete intermingling of two groups; that is, in com- plete fusion which would give to them common defensive limits, more extensive, and would coincide with a progress in interior organization.
On the contrary, in warlike societies the contest for the terri- torial and numerical extension of the group seems to be caused by the existence of conditions disadvantageous to the develop- ment of their normal life. This contest corresponds to an inequality of strength between the groups, and also to an inter- nal instability caused by the lack of proportion of the food supply and other resources to the population.
Economic difficulties appear in general to be the principal
