INTRODUCTION TO SOCIOLOGY 835
it has engendered conflicts. These variations have not ceased, nor will they cease, but will tend more and more to reproduce themselves by a process equally natural and more efficacious from now on one of mingling and of fusion, which will still further multiply the varieties, extending them, and reinforcing the fundamental and uniform characteristics of the species. These variations multiply and specialize more and more, and thereby they continue the work of adaptation at first realized by the races. We are in the presence, not of two contradictory natural processes, but of a unique law. It is not natural selec- tion, as is very often said, which is the cause of these variations. Natural selection is only the selective process which makes it possible that among the existing variations those which are advantageous to individuals and to society in the actual circum- stances are conserved. But now it has become more advantageous, for completing the conquest and assimilation of the earth by the human species, that mankind be divided into innumerable small groups rather than into a few strong groups. This infinite num- ber of groups, indispensable for the assimilation of the globe, now that its occupation by degrees, is nearly accomplished, is realized by the fusion of races. This fusion is a progress of variability, an extension, a perfecting of this law. The Darwin- ian law of the struggle for existence is not abolished, but transformed, reinforced by the law of the meaning of life.
After all that precedes, the reader is now able to catch a glimpse of the positive theory of social frontiers. The solution of the problem is neither in the preservation of the actual limits nor in their removal for the profit of a sentimental cosmopolitan- ism, vague and undetermined, under which is concealed too often an aristocratic individualism. Every social group is neces- sarily limited. The properties of the groups are the same as the properties of the materials of which the group is composed. The limitation of every society is a condition of its equilibrium, of its life, of its development. The existence of every society, special or general, is correlative with the existence of a social form. Form implies a boundary, a zone of separation between that society and its surroundings. But we have seen already from
