The ongoing debate about the relationship between European integration and social policy has compelled a growing number of researchers to adopt an historical perspective that compares European Union (EU)-level processes with social and political formations of the past, in order to draw lessons for the European project. One of the most crucial historical and sociological issues raised by the EU-social policy nexus concerns the possibility to expand the boundaries of social solidarity so as to include new populations and territories, beyond the existing domination of national forms of solidarity tied to the modern (welfare) state.

In Belonging, Solidarity and Expansion in Social Policy, to explore how the boundaries of solidarity can be expanded over time, sociologist Stefanie Börner (Free University of Berlin) analyses the role of mutual benefit societies in Germany and the UK during the nineteenth and the early twentieth century, before exploring the role they played, and the claims they put forward, during the emergence of national health insurance, which was enacted in 1883 and 1911, respectively. Focusing on health care, the book explores the relationship between social solidarity and the changing boundaries of belonging associated with the shift from local and occupational funds to the creation of national social insurance. For Börner, this key historical moment is full of lessons for the current debate on the Europeanisation of social policy, which is largely about the rescaling of social solidarities and territorial boundaries.

Based on systematic archival research, the empirical core of the book is devoted to the analysis of UK friendly societies and German benefit funds, which played such a central role before and during the advent of modern social insurance. Stressing the greater national integration of UK organisations and the more authoritarian approach of the German state, Börner suggests that, in both countries, mutual benefit societies largely opposed the advent of health insurance while providing a foundation upon which the state could build what would later become known as the modern welfare state. Through a detailed analysis of the arguments against and in favour of social insurance formulated by actors located within the field of mutualism, Börner studies how categories of belonging and boundaries of social solidarity are perpetually defined and redefined, a reality that has implications for both the analysis of welfare state development and the current debate on the creation of European social (policy) solidarity.

For the author, solidarity is a context-driven phenomenon related to collective identities and economic interests, a situation that makes the gradual redefinition of belonging, and of the frontiers of redistribution, possible. Consequently, because social policy institutions help shape the boundaries of belonging and redistribution, ‘solidarity is not a necessary precondition for successful institution building’ (p. 178). From an EU perspective, this means that the existence of pre-existing national solidarities and the relative weakness of European identity are not, in themselves, insurmountable obstacles to the emergence of transnational social policy. In her discussion about contemporary European integration, Börner uses the case of patient mobility within the EU to exemplify the advent of new forms of European social policy, which differ from policies associated with the national welfare state, and are closely related to the market logic of economic integration.

The author believes that, in Europe, there is currently a gap between economic and social integration that the development of supranational solidarity and social policy should fill. Recognising the domination of neoliberalism within the EU, she supports the expansion of supranational social policy as a way to create a more solidaristic, socially integrated transnational polity. The limitation of this normative vision is the author's implicit teleological assumption that solidarity always expands and becomes more universal, over time. In recent decades, however, the growing role in some countries of sub-state social policy and of welfare programs operated by voluntary, civil society organisations suggest that history is not only about the linear development of broader and broader forms of belonging and solidarity one can identify with progress.

Although Börner does not clearly recognise this, an important contribution of her work is to study voluntary forms of solidarity that have returned to the forefront of social policy debates, at least in a number of countries. In this context, state-level solidarity associated with the national welfare state has to compete with both sub-state and supranational attempts to redefine the boundaries of belonging, solidarity and social policy, in a compulsory as well as in a voluntary manner.

Importantly, at the supranational level, there is no reason why solidarity should remained confined within the boundaries of the EU. In fact if, as the author claims, economic exchanges are becoming increasingly global and that the economic and social sphere should expand hand in hand, would it be possible to claim that, in the long run, transnational solidarity should take a truly planetary scale, beyond ‘foreign aid’? The fact that Börner does not mention this far-reaching and perhaps utopian scenario points to the normative limits of the ‘European project’, which is about the creation of new boundaries (and therefore exclusions) rather than the creation of genuine universal solidarity, utopian or not.

Overall, despite such normative limitations that have nothing to do with the (superb) quality of the scholarship at hand, Belonging, Solidarity and Expansion in Social Policy is a well-researched and provocative book that offers crucial insight about the past, present, and future of social policy in Europe, and beyond.