Sociology is the study of how society functions, or in some cases, does not function. Various competing schools of sociology have attempted to fit observations of social phenomena into different conceptual systems. This work traces the origins of these systems from Enlightenment thought and the work of Auguste Comte to subsequent developments in Karl Marx, Herbert Spencer, Emile Durkheim and Max Weber. The rapid expansion of sociology in 20th-century America and Britain, the post-World War II dominance of Talcott Parsons, the Chicago School and the rise of Structuralism are outlined. Also examined are the array of concepts and methods of research that have been applied to the study of society.