On the other side of the spectrum, Constantinianism is characterized by an unmitigated fusion of church and state, such that the two basically become one. Proponents of this approach view civil government as a vehicle of God’s redemptive purposes in the world, and thus they believe that public policy should be an extension of the divine will. The magisterial reformer John Calvin is a great example of this outlook. For Calvin, the state is to be the mouthpiece of the church; the government is established in order to enforce the laws and commands of God.
Overall, I find both of these options to be unsatisfactory. Separatism does not take the Great Commission seriously enough. Christians are called to be “salt” and “light;” we are summoned to bear the very image of Christ in this world. In doing this, we are to draw all people to the living God. How can we accomplish this if we withdraw from the world, out of sight from the societies and cultures that God so badly desires to redeem?
At the same time, Constantinianism is far too optimistic; it simply does not take into account the depravity and sinfulness of humankind. Because political systems are run by fallible human beings, political systems will never be able to perfectly carry out the will of God. Power tends to be prone to corruption and thus is easily polluted. Historically, when church and state have been intimately wedded, and thus when the church has been endowed with a great deal of political power, the church has often fallen prey to coercion, manipulation, and outright violence. Furthermore, civil laws and legislation alone do not have the ability to transform hearts and renew minds; only the Spirit of God can truly change a person from within and thus procure true redemption.
Based on my general dissatisfaction with these two historic approaches, I would like to offer a third option: The “Christian engagement model.” Like separatism, the Christian engagement model emphasizes the importance of the church being holy and set apart. However, contrary to separatism, we do not withdraw from society, but engage every aspect of it. Like Constantinianism, this model stresses the need to dramatically impact the world for Christ. However, we do this through means of influence and persuasion rather than through coercion, control, and force. Christians are called to engage every area of human life with the gospel of Christ Jesus. Therefore, in opposition to the current landscape, Christians must have a voice in the marketplace; we must make our mark in the public square. The kind of compartmentalism that the privatization of religion demands is psychologically unhealthy and downright damaging to human society. Thus, the Christian engagement model calls for Christian voices in mathematics, philosophy, the arts, the sciences, politics and every human discipline imaginable.