In the history of political thought, few issues have been more central than the relationship between church and state, and few more complex and contested. From ancient times to today, thinkers have conceived of the connections between religious and political institutions in a wide variety of ways, with the two being sometimes combined, sometimes separated, and sometimes (in fact often) at odds. Christian writers have been particularly active in conceptualizing the relationship between church and state, and in applying those concepts to the modern nation‐state. But those from other religious traditions have contributed as well, as have secular theorists, inspiring an array of institutional relationships that ranges from theocratic regimes and established churches to secular states like today's France and Turkey, with multiple systems based on cooperation, neutrality, and strict church–state separation found in between. Moreover, while appearing to be static, relations between church and state are in fact quite fluid, changing frequently as a result of court decisions, public policies, and shifting political opinion. Today especially, with the appearance of religiously based political movements in many parts of the world, the issue has become even more complex and contested, as what was once seen as a dualistic and exclusive relationship between two dominant sources of power has become a multifaceted set of interactions that includes interest groups, social movements, and political organizations that engage in multiple forms of religious politics within civil society.