102 ADAPTATION AND PROGRESS 
factor. The only safe method, then, is to secure a sure basis, if 
possible, by an inductive study of the process itself and only 
after we have done this are we in a position to criticize fairly the 
school of writers whom we have just reviewed. 
Before passing to this inductive study, however, it will be neces- 
sary to consider another group of writers who have laid stress on 
the environment as the most important conditioning factor, and 
of these we shall consider briefly the contributions of four repre- 
sentative writers: Karl Marx making his approach through 
economics and philosophy, Buckle, through economics and sta- 
tistics, and Ratzel! and Ripley through an inductive study of the 
influence of the physical environment on individuals and social 
groups. 
1 As interpreted by Miss Semple. 
