My PhD thesis is a study of British social anthropology. It is told through shifting concepts of the 'primitive society' between the 1920s and the 1970s. Broadly speaking, academic anthropologists in Britain ceased to see 'primitives' as evolutionarily backward and increasingly began to relativize concepts of culture and society. Despite this general shift in social scientific discourse, anthropologists' ideas about the 'primitive' were often conceptually incoherent. Was a "primitive society", James Ferguson asks, "Pre-industrial? Pre-literate? Pre-modern? Pre-westernized? Pre-complex-organization?" Social anthropologists in the British tradition were supposed to be post-evolutionist but their discussions of the relative 'primitivity' of their subjects point to the latent assumptions of development nested within their functionalism. These tensions between relativism and evolutionism are explored in the five main chapters of my thesis.