This thesis considers, from a sociological viewpoint, the intellectual movement in Victorian Britain known as scientific naturalism. It argues that the naturalist cosmology needs to be seen as part of the strategy of certain social groups; in particular, naturalism expressed the interests of the newly emerging scientific profession in nineteenth century Britain. The professionalisation of science was part of a larger social development: the appearance of a 'new' professional middle-class. The thesis considers how other new professionals, especially those connected with medicine, deployed naturalistic formulations in their own attempts to secure social recognition and resources. An attempt is made to place naturalism in a broader historical perspective as well as to describe the intellectual background from which it emerged. There are six chapters. The first describes social conditions relevant to an understanding of naturalism; the next four discuss the leading themes of the naturalist world-view; the last considers the wider significance of naturalistic approaches to man and society at the turn of the nineteenth century.