Book 4 of 4 - External Means by which God Invites Us into the Society of Christ and Holds Us Therein
Chapter 20 - Civil Government
1-2 - How civil and spiritual government are related
1. We are under a two-fold gov't. One spiritual, the other regarding "civil justice and outward morality." We have to avoid the error of "overturn[ing] this divinely established order," and the error of flattering princes and letting them go "against the rule of God Himself." We may not mingle the spiritual and civil elements of government, though. "It is a Jewish vanity to seek and enclose Christ's Kingdom within the elements of this world." He makes clear in 1 Cor 7:21 that "spiritual freedom can perfectly well exist along with civil bondage" [sorry Patrick Henry!]
2. Civil gov't is distinct from spiritual, but "they are not at variance." The magistrate must protect the worship of God, defend sound doctrine and the sound church, "to adjust our life to the society of men, to form our social behavior to civil righteousness, to reconcile us with one another, and to promote general peace and tranquility." Some say the church should be sanctified enough to handle all problems, but mankind is too depraved and needs the power of the sword to punish and deter our evil.