INTRODUCTION 



THE purpose of the following essay is twofold ; in the first 

 place, to enforce the view that the process of evolution, 

 whether it be forward and in the direction of further develop 

 ment, or backward and degenerative, has never exhibited the 

 isolated advance or decay of any single principle in the 

 pairs of opposites, such as good and evil, pain and pleasure, 

 ignorance and knowledge, and many others, which enter 

 into the total complex of human nature ; but that, on the 

 contrary, when any one of the partners in any such a pair 

 has either grown or decreased, the other partner too has 

 shared the growth or decrease to an approximately equal 

 extent. The other half of our purpose has been to trace 

 the connexion of this principle with ethics, or the systematic 

 representation of our judgements on human conduct. 



No long account of the circumstances in which this essay 

 was produced is called for. The idea of evolution as the equal 

 and parallel progression of opposites was suggested to me, 

 while I was still an undergraduate, by the simultaneous study 

 of Herbert Spencer and Schopenhauer. My mind was already 

 prepared for its reception by the lesson taught by Tocqueville, 

 that in the republican institutions of America, when com 

 pared with the institutions of the old world, special advan 

 tages were nearly counterbalanced by special drawbacks. 

 At first my generalization only took in the contrasted pair 

 of pleasure and pain ; very soon it was extended to good 

 and evil ; and finally it came to embrace adaptation and 

 misadaptation generally, or, in other words, the whole of 

 the phenomena of life when regarded under the aspect of 

 evolution. At this point it was my lot to enter a service 

 whose absorbing duties left neither the leisure nor the 

 appetite for abstract speculation, and the theory was not 

 carried further. But it was far from being lost sight of. 

 I had been much impressed by an idea of its magnitude, 



