Lo and behold, Luther never used the term two kingdoms, and for good reason.
Luther talked about two hands or two realms. The left hand referred to the ways that God works through the world to promote the flourishing of creation. This, of course, refers to the just rule of states, but refers to any promotion of physical well being. God's left hand is at work in Habitat homes and soup kitchens, disaster response efforts and parenting classes, in local schools and in conservation efforts. The right hand referred to the particular work of achieving justification for people, which introduces salvation and Kingdom work immediately. Any time someone comes to relationship with God and the church, we see God's right hand at work. But this language is still clunky, and leaves us (or me, at least) feeling like a division or hierarchy exists in God's work.
Thank God for my friend Brandon Heavner, who pointed me to Craig Nessan's article "Reappropriating Luther's Two Kingdoms." Nessan suggests a reconsideration of the theology, where we refer to God's Kingdom as a singular entity (how biblical) and that God uses two strategies simultaneously to bring that kingdom to fruition (how sensible). Of course, God desires all God's creation to thrive physically, and so the left hand strategy seeks to promote flourishing, not only of humanity, but of all things. And of course, God desires all creation to have a restored relationship with their Creator, so through the work of Christ, the Holy Sprit, and the church, God's right hand strategy justifies sinners to become saints for the kingdom at hand.
This is a really powerful perspective, especially as we see the numbers and percentage of American Christians dwindling. God's not given up. God's left hand strategy is still vastly at work, even through offices of a shrinking denomination like the ELCA. For you see, work like the ELCA Malaria Campaign, Lutheran Disaster Response, and Lutheran World Relief reveal God's left hand strategy at work through the church. At the same time, though our numbers are not ballooning, the work of ELCA mission developers to reimagine how the church might foster spaces where people may meet with a God who cares deeply for them reveals an attempt to reorient the church to the right hand strategy of God.
The wonderful gift of this Two Strategy theology is the constant witness that God is not giving up on the world. Christ's Kingdom is coming, and the Holy Spirit is using two strategies to accomplish God's will on earth as it is in heaven. Thank God.