This introductory chapter outlines the problem of social order and the main argument of the book: that the question of what holds complex and diverse societies together has become – and has remained – a philosophical puzzle in modern political science, a presupposition that has been built into our concepts, theories, and normative commitments. Having outlined the argument, the contents and the structure of the book, the chapter then provides a short background for the problem of social order in political science. The chapter recalls how this problem emerged as such in modern social and political discourse in the evolution of the modern concepts of state, nation, and society and discusses how the relations among these concepts provided nineteenth-century political thought with a solution to the problem of social order predicated on a fusion of nationality and statehood.

This chapter examines the concept of solidarity, especially its existence outside the law, as a mechanism of cohesion. Three features are characteristic of this mechanism. First, solidarity mediates between the community and the individual. Second, as a result of solidarity, unity is created. Third, solidarity carries with it positive obligations, requiring individuals to act in support of, and in conformity with the group. Apart from these three general characteristics, solidarity is a multifaceted concept, with differing implications depending on the context in which it features. To understand these implications the chapter distinguishes between three kinds of solidarity: ‘social solidarity’, ‘welfare solidarity’ and ‘oppositional solidarity’. After a short discussion of each, the chapter pays special attention to social solidarity. On the basis of Aristotle’s notion of ‘friendship’, Rousseau’s ‘social contract’, Durkheim’s ‘mechanical’ and ‘organic’ solidarity and Parsons’s understanding of solidarity as a normative obligation, it analyses the concept’s roots and evolution over time.