INTRODUCTION 



THE field covered in this volume is wide and the treatment 

 in many parts is necessarily short and summary. In justi- 

 fication it must be said here that the book completes a 

 scheme which has occupied the writer for twenty-six years 

 and has been carried through successive stages in three 

 previous works. But in the meantime it was inevitable 

 that the scheme itself should change and expand, and the 

 precise aim of this final instalment will therefore be most 

 readily explained by giving a slight account of the manner 

 in which the subject developed in the writer's mind during 

 the somewhat extended period in question. 



In the middle of the " Eighties," when the writer was 

 first studying philosophy, the biological theory of evolution 

 was already very generally accepted, and the philosophical 

 extension of the theory by Mr. Herbert Spencer was, 

 except in academic circles, in the heyday of its influence. 

 Philosophically Mr. Spencer was not a materialist. But his 

 metaphysical safeguards did not rescue the evolution theory 

 from some of the most unfortunate consequences of a 

 materialistic system. Evolution, as thus interpreted, 

 meant, in its bearing on human life and action, essentially 

 two things. It meant that the human mind must be 

 regarded as an organ like the lungs or the liver evolved in 

 the struggle for existence with the function of adjusting 

 the behaviour of the organism to its environment. It was x 



