Two Kingdoms vs. Radical Two Kingdoms

Pastor Jason Stellman has twice (first time, second time) drawn my attention to a post from Darryl G. Hart disputing the "radical" label with respect to the radical form of two kingdoms theology that he (Hart) advocates (link). Stellman seems to think himself in agreement with Hart, though I cannot confirm that Stellman is aware of the extremes to which Hart takes his position.

Before we get to the meat of Hart's post, I'll address the question posed by Pastor Stellman in his second post: "Hart's point is that you don't get to call 2K folks historically "radical" if your tolerance of [Roman] Catholics and Mormons places you closer to us than to Calvin on the Christ/Culture spectrum." That is a fair point. While that may be a point that is valid with respect to Doug Wilson, it will not apply to present company.

Hart writes:

But to call two-kingdom theology “radical” is silly.

For starters, it is as old as Protestantism is itself. Now for some Reformed Protestants, historic Protestantism is tainted by Lutheranism. This is indeed a puzzle and deserves greater investigation. What is going on among conservative Presbyterians and Reformed that they so carelessly hurl around “Lutheran” as an epithet?

For the main course, two-kingdom theology among Presbyterians goes all the way back to the Adopting Act of 1729.

I answer:

Hart needs to be careful here. Wilson and others use the label "radical" not as a mere pejorative tag to the whole "two kingdoms" concept but as a description of a specific branch of two kingdoms theology that is, well, more radical than the traditional Reformed position.

The claim that it is "as old as Protestantism itself" is to claim that it is Lutheran. Hart does not provide any citation to back this up. I found the following on a Romanist cite that is critical of Luther:

“You are a prince or judge. You have people under you and you wish to know what to do. It is not Christ you are to question concerning the matter, but the law of your country. ... Between the Christian and the ruler, a profound separation must be made. ... A prince can be a Christian, but it is not as a Christian that he ought to govern. As ruler, he is not called a Christian but a prince. The man is Christian, but his function does not concern his religion. ... Though they are found in the same man, the two states or functions are perfectly marked off, one from the other, and really opposed.” (Luther’s Works, Weimar Edition, pp. 391, 439, 440.)

I cannot confirm the authenticity of this quotation, and I have only found it in a number of related Romanists sources. Nevertheless, it seems to reflect the general portrayal of Luther that can be found widely from a number of different sources. It does also seem similar to the view that Hart has expressed