PREFACE TO THE FOURTH EDITION. 



To the first edition of this work there should have been 

 prefixed a definite indication of its origin ; and the misappre- 

 hensions that have arisen in the absence of such indication, 

 ought before now to have shown me the need for supply- 

 ing it. 



Though reference was made in a note on the first page 

 of the original preface, to certain Essays entitled " Progress: 

 its Law and Cause," and " Transcendental Physiology," as 

 containing generalizations which were to be elaborated in 

 the " System of Philosophy " there set forth in programme, 

 yet the dates of these Essays were not given ; nor was there 

 any indication of their cardinal importance as containing, 

 in a brief form, the general Theory of Evolution, Xo clear 

 evidence to the contrary standing in the way, there has 

 been very generally uttered and accepted the belief that 

 this work, and the works following it, originated after, 

 and resulted from, the special doctrine contained in Mr. 

 Darwin's Origin of Species. 



The Essay on " Progress: its Law and Cause," coexten- 

 sive in the theory it contains with Chapters XV., XVI., 

 XVII. , and XX. in Part II. of this work, was first published 

 in the Westminster Review for April, 1857; and the Essay 

 in which is briefly set forth the general truth elaborated in 

 Chapter XIX., originally appeared, under the title of " The 

 Ultimate Laws of Physiology," in the National Review for 

 October, 1857. Further, I may point out that in the first 



