Michael J. White, Professor of Law and Philosophy at Arizona State University:
The social and political success of Christianity brings to the foreground, in particular, questions about the source of political authority and the legitimacy of political institutions. The concept of the Christian ecclesia, the church or community of the faithful, can confront the secular polis or state in a variety of ways: as a political rival; as an authoritative but benevolent senior partner (or subservient junior partner) of the secular state in the enterprise of attending to the welfare of the state’s citizens; as embodying a moral (or political) ideal against which that secular state may be measured; or as a spiritual community set apart from all secular states, the concerns of which are of an order entirely different from the concerns of such states.
— From “Christianity: A Political Religion?” in Political Philosophy: A Historical Introduction: Second Edition (Oxford)