In the debates over the two kingdoms doctrine people often focus on the nitty-gritty questions of application. Should the church preach against abortion? Should Christians send their children to public schools? Should the government promote Christianity? Of course, there are obvious reasons why people like to discuss what is practical.

But another reason why the conversations often devolve into this kind of tug-of-war is because people think of the two kingdoms doctrine as being about two different airtight realms, as if one set of institutions and activities can be placed in one realm, and another set of institutions and activities can be placed in the other, with the two being mutually exclusive.

The problem is, this is not what the two kingdoms doctrine has classically been about, and it is doubtful whether this kind of separation can be done in the way that some people seem to want to do it. Rather than understanding the two kingdoms doctrine in terms of two separate realms within this world, it would be more biblical and more faithful to the reformers to understand the two kingdoms based on the distinction between the present age and the age to come, between the created (and cursed) world and the kingdom of God. The two kingdoms doctrine is needed because the kingdom of God breaks into this age, without immediately destroying or transforming this age. There is an eschatological tension that somehow needs to be sorted out.

Calvin explains this dynamic very clearly in his explanation of the petition in the Lord’s Prayer, Thy Kingdom Come, in his Commentary on a Harmony of the Evangelists (Matthew 6:10). He writes,

We must first attend to the definition of the kingdom of God. He is said to reign among men, when they voluntarily devote and submit themselves to be governed by him, placing their flesh under the yoke, and renouncing their desires. Such is the corruption of the nature, that all our affections are so many soldiers of Satan, who oppose the justice of God, and consequently obstruct or disturb his reign. By this prayer we ask, that he may remove all hindrances, and may bring all men under his dominion, and may lead them to meditate on the heavenly life.

This is an incredible passage. Calvin is clearly defining the kingdom of God as God’s redemptive reign evidenced by the voluntary submission of human beings. In other words, the kingdom of God cannot be conflated with God’s providential sovereignty over all things, or even with the judgment that he exercises through civil government, which operates by the sword. How then does the kingdom appear to us visibly?

This is done partly by the preaching of the word, and partly by the secret power of the Spirit. It is his will to govern men by his word: but as the bare voice, if the inward power of the Spirit be not added, does not pierce the hearts of men, both must be joined together, in order that the kingdom of God may be established. We therefore pray that God would exert his power, both by the Word and by the Spirit, that the whole world may willingly submit to him… The substance of this prayer is, that God would enlighten the world by the light of his Word – would form the hearts of men, by the influences of his Spirit, to obey his justice – and would restore to order, by the gracious exercise of his power, all the disorder that exists in the world.

Again, Calvin is eminently clear here. The kingdom of God appears through the transformation of human beings by the power of the Word and Spirit, and it is inherently non-coercive. But note that this kingdom is not limited in its power to the proclamation of the Word. Rather, it is expressed through the way in which believers obey God’s justice, and in that sense it is reflected wherever order is restored in the world as a result of voluntary submission to God.

The problem, as Calvin notes, is that the world is still full of disorder and iniquity. And “to whatever extent iniquity abounds in the world, to such an extent the kingdom of God, which brings along with it perfect righteousness, is not yet come.” Calvin therefore explains that there is another way in which God reigns that must be distinguished from the kingdom of God:

There is still another way in which God reigns; and that is, when he overthrows his enemies, and compels them, with Satan their head, to yield a reluctant subjection to his authority, ’till they all be made his footstool.”

In other words, in this present evil age God restrains the wicked through coercion. He does this providentially but he also does it by means of civil government. Yet this part of God’s reign is in its very essence coercive and restraining. It does not build up the kingdom of God.

From this it is clear that while the two kingdoms doctrine is fundamentally about eschatology, it must be expressed institutionally. The state expresses God’s providential reign because it depends on the use of the sword. The church, on the other hand, administers the kingdom of God because it is the steward of the Word by which the Spirit operates.

And contrary to certain people, the Word and Spirit is at work in the spiritual government of the church not only in the preaching of the Gospel, but also in the exercise of the keys of the kingdom through church discipline (by pastors and elders), in the church’s declaration of doctrine, in the church’s worship of God, and even in the work of the deacons. That is why Calvin repeatedly identifies the kingdom of God with the church.

Although Calvin thought the state also has something to say about religion, he is clear that it does so only in the same restraining and coercive sense that God reigns apart from the kingdom of God. Even where the state can be said to build up the kingdom it only does so by providing outside support, that is, by promoting the work of ministers, who are the ones that truly build Christ’s kingdom.

From all this it is clear that the two kingdoms doctrine is better understood as a doctrine of two ages and two governments, rather than of two realms. For as the power of the kingdom extends in this present evil age, believers are to walk “in Christ” (that is, in the power of the kingdom of the age to come) in everything that they do. On the other hand, the world in which they do this still very much remains the present evil age, governed by God’s providential rule and by coercive government.

So while Christians may be living according to the laws and customs of this world, they are to do so in a way that is compatible with their allegiance to the kingdom of God. This is why it can be so difficult to iron out how Christians should act when engaging the various tasks and activities of this age. We are called to mix the age to come with the present evil age in everything we do, and that is no easy matter. This is, after all, the age of suffering service.

The classic example of this is Paul’s instruction to slaves and masters. In the kingdom of God there will be neither slave nor free. Yet Paul does not demand that Christians entirely separate themselves from the institution of slavery (which would have been impossible in that day). Instead, he calls masters and slaves to treat one another lovingly “in Christ.” Of course, this undercuts the very sinful rationale that undergirds the institution of slavery, and if Christians faithfully follow their Lord the resulting institution simply will not be slavery as the world understands it (this explains why the Southern Presbyterian doctrine of the spirituality of the church was misapplied. The Southern Presbyterians were right to argue that slavery is not inherently sinful, but they underestimated the degree to which the Gospel transforms the institution, and they utterly failed to discipline their members consistent with that Gospel).

The same could be said about marriage, although unlike slavery marriage is a divinely created institution. Jesus says there will be no marriage in the kingdom of God, and Paul indicates that in Christ there is no male nor female. Nevertheless, Christians still remain in this world, and so they cannot pretend that gender, sexuality, procreation, and care for children do not exist. Indeed, Christians are still bound by God’s natural law in all of these elements of the created order. Even here, however, Christians are to act in such a way as to communicate that these relationships and callings are not ultimate. Husbands and wives love one another after the model of the relationship between Christ and the church, and children obey their parents “in the Lord.”

For all the debate and argument over the two kingdoms doctrine, I suspect that Christians actually agree about virtually all of this. What we usually argue about is the application. But it would at least be helpful if we understood where we agree and where we disagree. There is enough to argue about without having to invent disagreements where they do not exist.

Matthew J. Tuininga is a doctoral candidate in Ethics and Society at Emory University, holds an MDiv from Westminster Seminary California and is licensed to preach in the United Reformed Churches in North America. He blogs at Christianity in America, where this article first appeared; it is used with permission.