There are a number of dualisms that often come up in discussions of political theology. Many of these bear resemblances with one another, even while they remain distinct–which is to say, some of them share similarities rather than identity. Below I’ve tried to sketch out what is proper to each one of these dualisms. Obviously there is more (very much more) that can and really should be said; but I have tried to be brief in order to bring out the main points. If I had the skills of, say, Kyle Dillon, I would have put these in an eye-catching chart, but I do not. So you just get a list instead.
Two Cities: (1) The city of God (heavenly city) and (2) the city of man (earthly city, city of the devil). These two entities are exclusive of one another, contain angels as well as men, and are governed by different loves (love of God and love of self). Roughly, the elect (or true Christians) and the non-elect (unbelievers). In the progress of history, the citizens of these two cities are mixed together, and will only be finally separated at the Last Judgment. Thus the cities are both a present and an eschatological reality. The citizens of the respective cities include both those alive now and those who have died. The distinction does not map easily on to any earthly structures in a one-to-one sort of way, though the distinction has relation and relevance to earthly structures.
Two Kingdoms: (1) The spiritual kingdom and (2) the earthly, or common, kingdom. If the two cities have to do with citizenship, the two kingdoms have to do with rule. Both kingdoms are ruled by the theanthropos, the ascended and enthroned God-Man Jesus Christ, but they are administered in different ways. In the spiritual kingdom, Christ rules in the heart of the Christian immediately by the Holy Spirit through faith. This realm is internal (at present). In the common, or external, kingdom, Christ rules mediately through his agents, whether in an ecclesiastical or a political setting. Thus the institutional church is governed by the ministerium, the servants of God, and the civil order is governed by the magisterium, also servants of God. All aspects of temporal order fall under the common kingdom.1
Two Churches: (1)The visible church and (2) the invisible church. The visible church is all of those throughout the world who profess the Christian faith, together with their children. The invisible church is the whole number of the elect, and encompasses the past, present, and future. In this way it is similar to the city of God, although not identical because it does not include angels. The visible church can in a sense be (and sometimes is) called the Kingdom of Christ, because Christ rules it by his Word, the Gospel. On the definition given in the first sentence, the visible church is not to be identified with the institutional church, as though the church properly speaking is the ministerium. Rather, officers represent a people who are already themselves kings and priests, and they govern and guide that people in this life. When the ministerium is referred to as “the church,” it is only by way of synecdoche.
Two Orders: (1) Church and (2) state. In this dualism, what is referred to is the governing structures of two different divine institutions, namely, ministerium and magisterium, ministers and magistrates. Each order has its own officers, and the offices they hold, with their attendant duties, are different: the former relate to the ecclesiastical order, the latter to the civic order. It is possible for both groups to serve one public, one body of citizens, but they do so in different ways.