The notion of cultural plurality and the idea of intercultural dialogue have been central to the discussion of cosmopolitanism in both political philosophy and social theory. This point is developed in an exposition of the arguments put forward by Immanuel Kant and Hannah Arendt and through a critical engagement with Ulrich Beck's social theory of cosmopolitanism as a “social reality.“ It is argued that Beck's analysis fails to convince as a sociological extension of a long philosophical tradition and that instead of Beck's macrostructural analysis it is more promising to formulate an actor-centred sociological theory on the transnationalization of social spaces and the formation of a “cosmopolitan“ consciousness or awareness of transnational actors.