The relationship between cosmopolitanism and social theory cannot be reconstructed directly. What we commonly refer to as the leading fi gures in the history of social theory – Marx, Weber, Durkheim, Simmel, Parsons – did not write much, if at all, on cosmopolitanism. True, in the Communist Manifesto Marx and Engels (1976) used the term loosely as an adjective to describe the new kind of cultural artifacts with world-wide orientation that were being created in capitalism. Thus, although they spoke of “cosmopolitan” literature and science – the German term they used there was Weltbürgertum – this hardly amounts to a systematic treatment or valuation of it as an idea. More poignantly, in his lectures on political sociology Émile Durkheim (1992) used the notion of cosmopolitanisme to recover Kant’s idea of perpetual peace as he tried to reconcile the old natural law cosmopolitan credo with the nascent force of nationalism just before World War I. But again in this case the highly politicized meaning Durkheim gave to the concept does not warrant, at least without further ado, depicting his sociological viewpoint as cosmopolitan. This chapter therefore begins with a note of caution. The assessment of the connections between cosmopolitan thinking and social theory cannot replicate the paths followed by those who have reconstructed how social theory relates to a number of alternative social and intellectual trends: the rise of capitalism (Giddens 1971) and the critiques of the Enlightenment (Hawthorn 1987), liberalism (Seidman 1983), Romanticism (Nisbet 1967), and nationalism (Chernilo 2007a). Rather, we need fi rst to identify the defi ning elements of cosmopolitanism as an intellectual tradition and only then can we attempt to move on and assess the extent to which they are compatible with the modern social theory’s main features.