This chapter focuses on how the principle of nationality was developed in the nineteenth century. It begins with a brief historical background, and then focuses on how the principle of nationality was developed after 1800. The chapter argues that this took place in four broad phases: nation as civilisation, as historic, as ethnic and as racial. It traces the escalation of the principle of nationality, from civilisational claims in France and Britain, to arguments of historic nationality for Germans, Italians, Magyars and Poles, followed by subordinate cultural groups using notions of vernacular culture, popular religion and ethnicity. The increasingly populist function of political language pushed discourse in an ethno-cultural direction, even where there existed an earlier tradition of framing nationality in elite terms. By 1914, the language of nationalism dominated political discourse. The formation of nation states in Europe advanced this process.