This chapter concerns the roots and increasing diversification of cosmopolitan social thought and the research it inspires. It shows that cosmopolitan matters now constitute central topics for research, debate, and controversy across the social sciences. Having begun as a sense of non-national affiliation – declaring oneself to be a ‘citizen of the world’ rather than of any specific polity – it now encompasses a much wider range of issues. Cosmopolitanism today simultaneously refers to a scholarly field, a set of research agendas, a series of substantive phenomena, moral and ethical norms, ideals and practices, and ways of thinking, both socially and politically, as well as in more purely academic terms of analysis and research procedures. ...