Thinking about BordersAn increasing concern with networks and mobilities, especially in the context of thinking about globalization and cosmopolitanism, has stimulated theorizing on the changing nature of borders. It is necessary to distinguish approaches which draw attention to the changing role of political borders in a globalizing world (for example, as revealed by shifting the focus of sociology from the nation-state to the globe) from others that attempt to theorize the changing relations between borders and society. It is the latter approach that interests us here: theorizing borders also involves an attempt to understand the nature of the social. Not surprisingly, therefore, theorizing borders and the dynamics of bordering and rebordering have become key components of understanding contemporary social and political change. Many of the themes central to contemporary social theory -globalization, cosmopolitanism, networked community, mobilities and flows -have led to both a rethinking of the nature and role of borders, and, at the same time, have caused social theorists to place borders more centrally in the study of society. As pointed out by Jan Nederveen Pieterse, '[a] global sociology is taking shape around notions such as social networks (rather than "societies"), border zones, boundary crossing, diaspora, and global society ' (2004: 81). In short, borders are central to the social theory agenda: to theorize mobilities and networks is at the same time to theorize borders.Social theorists have generally favoured one of two broad approaches to theorizing borders, although these are by no means mutually exclusive. On the one hand, borders have been contextualized by the idea of the network, which has shaped much current thinking on society, particularly under the influence of globalization theories. The network, along with associated ideas of mobilities, flows, fluids and scapes, has become a key metaphor for understanding modern life in a 'world in motion'. Urry's (1999) call for a sociological shift from the study of societies to the study of mobilities, Sassen's (2002) work on networked cities, and Wellman's (2001) idea of 'networked individualism' have all helped to advance this agenda. However, the work of Manuel Castells is perhaps the most celebrated in this field. The network society is one where a space of places (the territorial nation-state) is being replaced by a space of flows, and the European Union is seen as the paradigm of the network state (Castells, 2000). In the