We have demonstrated that the socialism which characterizes the end of the nineteenth century and which will illumine the dawn of the coming century is in perfect harmony with the entire current of modern thought. This harmony manifests itself even on the fundamental question of the predominance given to the vital necessity of collective or social solidarity over the dogmatic exaggerations of individualism, and if the latter at the close of the last century was the outward sign of a potent and fruitful awakening, it inevitably leads, through the pathological manifestations of unbridled competition, to the “libertarian” explosions of anarchism which preaches “individual action,” and which is entirely oblivious of human and social solidarity.
We now come to the last point of contact and essential oneness that there is between Darwinism and socialism.
 Sociologie criminelle, French trans., Paris, 1892.
 I cannot consider here the recent attempt at eclecticism made by M. Fouillee and others. M. Fouillee wishes to oppose, or at least to add, to the naturalistic conception of society the consensual or contractual conception. Evidently, since no theory is absolutely false, there is even in this consensual theory a share of truth, and the liberty of emigration may be an instance of it—as long as this liberty is compatible with the economic interests of the class in power. But, obviously, this consent, which does not exist at the birth of each individual into such or such a society (and this fact of birth is the most decisive and tyrannical factor in life) also has very little to do with the development of his aptitudes and tendencies, dominated as they are by the iron law of the economic and political organization in which he is an atom.
THE “STRUGGLE FOR LIFE” AND THE “CLASS-STRUGGLE.”
Darwinism has demonstrated that the entire mechanism of animal evolution may be reduced to the struggle for existence between individuals of the same species on the one hand, and between each species and the whole world of living beings.
In the same way all the machinery of social evolution has been reduced by Marxian socialism to the law of the Struggle between Classes. This theory not only gives us the secret motive-power and the only scientific explanation of the history of mankind; it also furnishes the ideal and rigid standard of discipline for political socialism and thus enables it to avoid all the elastic, vaporous, inconclusive uncertainties of sentimental socialism.