A Christian state or mundus Christianus is not easy to define. It is perhaps one where the public, legal and constitutional institutions are “Christian”. (I shall leave to one side for a moment the problem of defining precisely what I mean by Christian.) T. S. Eliot believed that the Christian state was “the Christian Society under the aspect of legislation, public administration, legal tradition and form.” The “state” can refer to the country, nation, society or culture as a whole or, only to the set of governmental institutions within a country. The latter, narrower meaning is the one I wish to adopt here. I shall define the state as “the set of distinctive institutions whose authority is recognised as legally binding within the territory.”
A theocracy is undoubtedly a Christian state, indeed one par excellence. I shall refer to theocracy as a “type 1” Christian state, for here both form and substance coincide. By theocracy I mean the situation where there is ecclesiastical supremacy and the state machinery is used to further particular religious interests. The early Jewish nation, Geneva under Calvin and various Islamic states around to the world today are examples of type 1 states. In this monistic polity, membership of the church (using that as a generic term for a religious organisation) and membership of the state are coterminous. Full rights as a citizen turn upon whether one is member of the church; those outside the church are second-class citizens. But a Christian state need not necessarily be a theocracy.