PREFACE TO THE AMERICAN EDITION. i x 



idea of the course and character of the discussion may be 

 formed by observing the titles to the chapters, which are as 

 follows : 



Part First: I. Organic Matter; II. The Actions of 

 Forces on Organic Matter; III. The Reactions of Organic 

 Matter on Forces; IV. Proximate Definition of Life; V. 

 The Correspondence between Life and its Circumstances; 

 VI. The Degree of Life varies with the Degree of Corre- 

 spondence; VII. Scope of Biology. Part Second: I. 

 Growth ; II. Development ; III. Function ; IV. Waste and 

 Repair; V. Adaptation; VI. Individuality; VII. Genesis; 

 VIII. Heredity; IX. Variation; X. Genesis, Heredity, and 

 Variation; XL Classification; XII. Distribution. 



The Principles of Biology will be followed by the Princi- 

 ples of Psychology; that is, Mr. Spencer will pass from the 

 consideration of Life to the study of the Mind. This subject 

 will be regarded in the light of the great truths of Biology 

 previously established ; the connexions of life and mind will 

 be traced ; the evolution of the intellectual faculties in their 

 due succession, and in correspondence with the conditions 

 of the environment, will be unfolded, and the whole sub- 

 ject of mind will be treated, not by the narrow metaphysical 

 methods, but in its broadest aspect, as a phase of nature's 

 order which can only be comprehended in the light of her 

 universal plan. 



The fourth work of the series is Sociology, or the science 

 of human relations. As a multitude is but an assemblage of 

 units, and as the characteristics of a multitude result from 

 the properties of its units, so social phenomena are conse- 

 quences of the natures of individual men. Biology and Psy- 

 chology are the two great keys to the knowledge of human 

 nature; and hence from these Mr. Spencer naturally passes 

 to the subject of Social Science. The growth of society, 

 the conditions of its intellectual and moral progress, the de- 

 velopment of its various activities and organizations, will be 

 here described, and a statement made of those principles 



