ABSTRACT
DESPITE the important rôe which the idea of social class has played both in social theory and in political movements, very few scientific studies exist of the nature of class differentiation and its conditions. Marx and his followers have sought to relate the various forms of social stratification to modes in the forms of production, but it would seem on an inadequate inductive basis, at any rate as far as modern conditions are concerned. In recent times efforts have been made, under the influence of biological ideas, to determine the relation between forms of social groupings and differences in physical and mental characters between individuals and groups. These are held to afford material for the agencies of social selection and thus to influence social differentiation in greater or lesser degree. But studies on these and other lines have suffered from the absence of an adequate classification and the lack of agreement with regard to the criteria of class, which makes effective comparison of the results arrived at by different investigators extremely difficult and precarious.
