John Calvin significantly modified Martin Luther's original two kingdoms doctrine, and certain neo-Calvinists have adopted a different view known as transformationalism.
[3] God has therefore ordained two regiment(s): the spiritual which by the Holy Spirit produces Christians and pious folk under Christ, and the secular which restrains un-Christian and evil folk, so that they are obliged to keep outward peace, albeit by no merit of their ownThis law-gospel distinction parallels and amplifies Luther's doctrine of Christians being at the same time saint and sinner, a citizen of both kingdoms.
Lutherans were content to allow the state to control the administration of the church, a view in the Reformed world shared by Thomas Erastus.
In general, however, the Reformed followed Calvin's lead in insisting that the church's external administration, including the right to excommunicate, not be handed over to the state.
The people in the kingdom of the world are equipped for fighting with carnal weapons—spear, sword, armor, guns and powder.
[1]Luther's articulation of the two kingdoms doctrine had little effect on the practical reality of church government in Lutheran territories during the Reformation.
[10] However, Calvin was able to establish after significant struggle in Geneva under the Ecclesiastical Ordinances, a form of church government with much greater power.