xiv Preface 



which compel the reader to reach those conclusions 

 and no other. The reader is not offered a set of 

 irrefragable laws which he must believe, but certain 

 preliminary considerations which, in the opinion of 

 the author, effect a clearing of the ground upon 

 which the foundations of a biology may some day 

 be laid. 



" The term Biology is used by the author to 

 signify the interpretation rather than the mere 

 description of life. The Biology, therefore, in the 

 interpretative sense, put before the reader is not 

 a nearly complete fabric the main constructional 

 lines of which have been laid down once and for 

 all, and the completion of which will consist in the 

 filling in of detail ; but a tentative indication of 

 the direction in which some approximation to an 

 understanding of life may be sought. 



" The main constructive thesis of the book is 

 the idea, which we owe to Samuel Butler, that the 

 details of the process of evolution can be studied 

 most minutely in man, in whose extra -corporeal 

 organs, his weapons, implements, and machinery, 

 evolution is proceeding with great rapidity. 



" This study of the evolution of human detach- 

 able implements leads on to M. Bergson's thesis 

 that the human intelligence owes its essential traits 

 to the fact that it was developed pari passu with 

 the acquisition by man of his control over matter. 

 Upon this conception of the human intelligence 

 rests the main critical thesis of the book, which is 

 the attempt to show that natural selection was 

 acceptable as an explanation of evolution, because 

 it was an explanation in terms of matter, and 



