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Introduction 



The idea of evolution. — Its application to inorganic things, to 

 organisms, to the origin of man and to man's psychical 

 life. — Its bearing upon ethics and social science. — Its special 

 province: natural science. 



THE present generation is so familiar with the 

 various doctrines which constitute our modern 

 scientific creed, in particular with its fundamental 

 tenet, the idea of evolution, that it is apt to forget 

 entirely how very recently this idea became current, 

 and through what struggles it has forced its way into 

 science. 



The idea of evolution has come to be one of the 

 most, if not the most inclusive of generalisations at 

 the present time; it extends far beyond the bounda- 

 ries of the sciences in which it had its inception and 

 covers every department of human thought not ex- 

 cluding even the most obscure and arduous problems 

 of philosophy. 



Taken in its broadest sense, it is closely allied with 

 the idea of causality: nothing can happen without a 

 cause, nothing can disappear without leaving traces; 

 all things have their origin in the things which pre- 

 cede them and engender the things which follow 



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