PREFACE TO THE AMERICAN EDITION. 



The System of Philosophy now in course of publication by 

 Mr. Herbert Spencer begins with a volume of First Princi- 

 ples^ which was republished in this country a year or two 

 since. The subject of Biology comes next in order, and is to 

 be treated in two volumes, of which the present is the first ; 

 Volume II. will probably appear toward the close of the year, 

 In accordance with the author's plan, the doctrine or method 

 of Evolution unfolded in First Principles and applied to Biol- 

 ogy in the present work, will be carried out in the subsequent 

 treatment of the Principles of Psychology and the Principles 

 of Sociology. 



In the preface to the English edition, Mr. Spencer remarks : 



"The aim of this work is to set forth the general truths of 

 Biology, as illustrative of, and as interpreted by, the laws of 

 Evolution: the special truths being introduced only so far as 

 is needful for elucidation of the general truths. 



"For aid in executing it, I owe many thanks to Prof. Hux- 

 ley and Dr. Hooker. They have supplied me with information 

 where my own was deficient ; and in looking through the 

 proof-sheets, have pointed out errors of detail into which I 

 had fallen. By having kindly rendered me this valuable assist- 

 ance, they must not, however, be held committed to any of 

 the enunciated doctrines that are not among the recognized 

 truths of Biology." 



New Yoke, March, 1866. 



