The contemporary vocal critics of modern 2k often remark that everyone is 2k, meaning that it is wrong for modern 2k advocates to paint them as 1k. The Roman Catholic expression of 2k doctrine qualifies that claim in important ways. First, it suggests that not everyone is 2k since the Eastern Church allowed itself to be absorbed by the state in the form of Caesaropapism. Second, it reveals that Roman Catholics also believe in the two-kingdoms, especially the idea that the church is and should be free from the state. (Rome would apparently not favor the language of the original Westminster Confession which gives the magistrate power to ensure that church counsels follow Godâ€™s mind.) In which case, if part of the point of the 2k doctrine is to separate the church and the state, and the papacy was an important institution for introducing and preserving that autonomy in the West, then the critics of modern 2k may want to explain how their 2k avoids the problems pointed out in the following (i.e., a Leviathan state) without also embracing the papacy. Of course, the other alternatives are Constantine or King David, but not if you want to be 2k along with everyone.
. . . the Church, always maturing as she groped for a just balance in her relations with the state for eight hundred years, finally broke in two, each part exhibiting a possible alternative solution to the problem. In the Eastern half of the Christian empire, in the new Rome founded by Constantine, divided from the West by her inheritance of Hellenistic culture and continuing the division of the empire into two blocks existing from the time of Diocletian to that of Theodosius, the Church succumbed to the States. Or would it be more exact to say that the state succumbed to the Church? . . . The other alternative has had even a greater historical role to play. In the Latin West, the Church, under the guidance of the Pope and her bishops, vindicated her freedom before the state. In this she was helped by a variety of external developments. Not the least of these is the fact that in the West, the Roman Empire collapsed in the fifth century, and the papacy remained the only rock of cultural unity among the states that rose in the aftermath of the invasions. It is often said that the freedom of the Western Church was built only on the ruins of the civil power; but the Church had in fact defended her freedom against the Emperor Constantius and later against Byzantine despotism, which weighted heavily on Rome and the West from the sixth to the eighth century. What favored the Western Churchâ€™s victorious struggle for her freedom was, above all, the fact that in Latin culture the sense of human freedom, especially religious freedom, had deeper roots than in the East. . . . But the most important internal resource from which the Western Church drew renewed strength in her struggle for freedom was the guiding role of the papacy, growing increasingly conscious of the rights granted to it by Christ as it sought to respond to the needs of a Church basically solid but ever struggling even in a Christian empire. It is a fact grasped not only by faith but also seen in history that all the churches who wish to withdraw from the unity of the Church dogmatically first of all seek refuge with the state but soon are absorbed by the state and fall with it. (Hugo Rahner, Church and State in Early Christianity , pp. xiv-xvi)