The study of social cohesion and solidarity, and their antitheses, social fragmentation and dissension, are central components of sociology. From the very beginnings of sociology right through to the present day, sociologists have endeavoured to identify the forces that either unite people into particular social configurations, or force them apart into diverse and often antagonistic groups. Any adequate understanding of social life must foreground issues of social coherence and divergence, unity and disunity, cohesion and fracture, order and disorder. This set brings together for the first time, in a thoroughly systematic and comprehensive fashion, the major sociological works on the above themes, from the period of the infancy of the discipline through to the present.