CH. xvm.] THE EVOLUTION OF SOCIETY. 201 



earth's surface, the Turks have never directly aided the 

 progress of civilization. Secondly, how was it that the Arabs 

 ever came to leave their native deserts and to couquer the 

 region between the Pyrenees and the Ganges ? Was it 

 because of a geologic convulsion ? "Was it because the soil, 

 the climate, the food, or the general aspect of nature, had 

 undergone any sudden change ? One need not be a profound 

 btudent of history to see the absurdity of such a suggestion. 

 It was because their minds had been greatly wrought upon 

 by new ideas ; because their conceptions of life, its duties, 

 its aims, its possibilities, had been revolutionized by the 

 genius of Mohammed. The whole phenomenon requires a 

 psychological, not a physical, explanation. 



The environment in our problem must, therefore, not only 

 include psychical as well as physical factors, but the former 

 are immeasurably the more important factors, and as civiliza- 

 tion advances their relative importance steadily increases. 

 Bearing in mind these preliminary explanations, let us now 

 address ourselves to the problem of social evolution, applying 

 to the solution of it sundry biological principles established 

 in previous chapters. We have first to observe that it is a 

 corollary from the law of use and disuse, and the kindred 

 biologic laws which sum up the processes of direct and 

 indirect equilibration, that the fundamental characteristic of 

 social progress is the continuous weakening of selfishness and 

 the continuous strengthening of syTnpathy. Or — to use a more 

 convenient and somewhat more accurate expression suggested 

 by Comte — it is a gradual supplanting of egoism by altruism. 



In the course ui" our inquiry into the causes of organic 

 evolution, it was shown that all the processes cooperating 

 in the development of higher from lower forms of life, are 

 in the widest and deepest sense processes of equilibration. 

 The all-important truth was there demonstrated, that the 

 progress of life on the earth has been the continuous equilibra- 

 1 See above, chapters xii. and xiii. 



