William Mcdougall 
The Group Mind [EPUB ebook] 

Group Psychology itself consists properly of two parts, that which is concerned to discover the most general principles of group life, and that which applies these principles to the study of particular kinds and examples of group life. The former is logically prior to the second; though in practice it is hardly possible to keep them wholly apart. The present volume is concerned chiefly with the former branch. Only when the general principles of group life have been applied to the understanding of particular societies, of nations and the manifold system of groups within the nation, will it be possible for Social Psychology to return upon the individual life and give of it an adequate account in all its concrete fullness.