"The visible Church . . . is the kingdom of the Lord Jesus Christ...."
Westminster Confession of Faith, xxv.2"The Roman Catholic Church holds that the visible and invisible church are very closely linked and that the visible church is the institutional church. In other words, the Roman Catholic Church is the Kingdom of God on earth. The immediate implications of this for everyday life are far-reaching. The world is divided into two realms, first, the realm of grace, which is the Kingdom of God or the church, and, second, the realm of nature, which is the rest of the world. As a consequence, the only way in which the home, the school, and the government can be linked with God is through the institutional church, in that they possess no direct relationship with Christ and hence no direct relationship with God. Their relationship being mediated and subordinate to the institutional church, it becomes necessary for the state, school and home to be under the authority of the church in every avenue of life, and, as members of an inferior realm, the realm of nature, to be under constant suspicion and guard. … To define the kingdom of God or the visible church in terms of the institutional church is to take the road to Rome, to drift toward the subordination of every avenue of life to the church. Many Protestants indeed share in this position and view every avenue of life with suspicion apart from ecclesiastical domination. But for us the biblical church, the kingdom of God on earth, is to be identified with the reign of God in the hearts of men wherever they are. Consequently, we must hold that the Christian home is a part of the visible church, as is the Christian school, the Christian state, and the Christian man in his calling, godly men everywhere in their calling serving as priests of the Kingdom of God on earth. … Consequently, the institutional church is definitely not one area above all the other areas of life, but is one aspect of the Kingdom of God on earth among many others. For us, therefore, the institutional church together with and not above the school, the home, the Christian man in whatever calling or sphere of activity is his, equally represents the visible church, the Kingdom of God."
(R.J. Rushdoony, Intellectual Schizophrenia, p. 41-42)