I spoke at Jordan Cooper’s “Just & Sinner” conference, the topic of which was the doctrine of the Two Kingdoms. This is a teaching that many people are confused about, including some Reformed folks who are trying to adapt it to Calvinism. In my first talk, I explained why this teaching is NOT dualism; nor does it mean an uncritical acceptance of the status quo; nor does it mean that Christianity has nothing to say about secular issues.
Rather, the Two Kingdoms is a way to bring together two different kinds of reality, under the One King. God governs the temporal, physical kingdom by means of His creation, His Law, His providence, and His working through human vocations. While the Two Kingdoms does show Christians how we can function in the secular world (since He is there too, though hidden), it also gives us a basis for criticizing the evils and untruths we will find there. Denials of His creation, the rejection of moral reality, the view that existence is meaningless, and attacks on vocations such as marriage and parenthood are NOT in accord with the Two Kingdoms.
Christians CAN apply moral standards (that is, the first use of the Law) to the world, though no one can be coerced into the spiritual kingdom, which is governed by the Gospel of forgiveness through Christ.
Anyway, if you want to see and hear what I had to say, follow the links here.