8 INTRODUCTION 
Two other methods are suggested in Professor Carver’s Sociol- 
ogy and Social Progress. In the Introduction he analyzes 
adaptation as passive and active material and passive and 
active social. We might, then, trace the development of each 
form of adaptation from Comte to the present. The difficulty 
here is that several authors have made contributions bearing on 
each of these four divisions, and such a method would make 
impossible the study of the social theory of an author as a whole. 
A third method might follow the outline in the book referred to, 
and discuss the development of the doctrine from the side of 
biology, economics, psychology and the social sciences including 
religion. But our chief interest is to study social theories rather 
than the writings of economists and social scientists except as 
they bear directly on the subject in hand, and here, again, as in 
the previous case, some authors have contributed along several 
different lines. 
It seems best, therefore, to discuss the social theories of the 
writers who have been most influential in the development of this 
doctrine of adaptation or whose contributions are most important 
in a constructive social philosophy built around this concept, and 
in an order which shall be, so far as possible, both historical and 
logical. In the treatment of some writers attention will be given 
only to their specific contribution to our subject while in the case 
of others a brief outline of their general social philosophy will be 
necessary as a background for a due appreciation of that contri- 
bution. The work as a whole will thus furnish an approach to a 
constructive social philosophy by a review of the systems of many 
writers not only in English but also in German and French. 
Definition of Terms.— Adaptation may be considered as a state 
or as a process.!_ By the former is meant such relationship be- 
tween an organism, species, social group or institution as is 
favorable to existence and growth; by the latter is meant the 
process by which such a unity becomes and continues in favorable 
relation to its environment. There are two general classes of 
environment, physical or material, and spiritual, including social, 
and two general classes of adaptation, passive and active. By 
1 Cf. Haeckel, The Last Link, pp. 84, 117 f. 
