204 THE CAUSATION OF DISEASE. 



that of the body : which man do we account the stronger, 

 the muscular or the intellectual — which in the battle of life 

 comes to the fore ? Among savage communities bodily and 

 mental superiority take about equal shares in giving one man 

 an advantage over his fellows, but among civilized peoples, a 

 man who is, so to speak, a mere walking brain, can command 

 the destinies of nations. Thus, among the latter, natural selec- 

 tion is not so much a matter of life or death as of personal and 

 social well-being. If, however, man had no morality prompt- 

 ing him to help the weaker, we may be pretty sure that the 

 fool would go to the wall, not only in the sense of sinking in 

 the social scale, but in the matter of life or death. Intellectual 

 superiority would be the great criterion of fitness if — as it 

 probably would — the absence of morality did not prevent this, 

 and thus, in the course of time, there would be an accumulation 

 of mental superiority by natural selection, and consequent 

 rapid mental evolution. As it is, there is a tendency to remain 

 at a certain fixed mean, intellectual and physical, for the clever 

 man marries a stupid wife and the clever woman a stupid 

 husband, and, in like manner, physical strength unites itself 

 with physical weakness. 



