It is far beyond the bounds my ability to adequately describe or defend theonomy, today at least. If you're not familiar with this term, here is a good start on the matter.
What I would simply like to do is invoke a familiar experience and hope to provide what it is that bothers me about an issue that I often find myself shamefacedly defending. Other times I go the route of the covert operative, and conceal my sympathy with my view.
Ultimately, the bumper sticker/t-shirt/cliche has it right.
What strikes me about this debate about ethics and law is that the precondition for living under a godly civil government, in terms of its explicit foundations and legislation is a plurality or majority of godly people who are dedicated to such a concept. Thus, I would like to argue that almost every problem associated with theonomy is an instance of the "5 year old with the car keys" fallacy. Just as Greg Bahnsen created a fallacy that became infamous (or famous, depending on your view) during his debate with Gordon Stein, in describing the "cookies in the cookie jar" fallacy, I would like to make a new term for the problem with theonomists as they have existed throughout the years. For, just as a small child thinks he or she knows what to do with a car, the boldness of most theonomists is actually based on an overemphasis on abstractions over reality.
For just as a 5 year old has no firm grasp or concept of what life would be like as someone who is old enough to drive, the theonomist who raises eyebrows with his or her outlandish claims has no firm grasp of what life would be like if Christians were living godly lives as the plurality/majority of society. Sure, one can look back to certain epochs, but in many ways that's just as helpful as the 5 year old looking at their siblings who drive. It may help one understand the shadow of the matter, without providing any substantial grasp of the matter.
As a result, we must be wary of any 5 year old who thinks they know exactly what they would do if they had a driver's license today. Similarly, the theonomist who ignores their status as a minority and focuses on Biblical ethics as an abstract principle becomes disconnected from reality to the point where the outlandish ideas and claims that have been made by some (but will not be recounted here) come up.
To be fully punny, what I am "driving" at is this: we should understand our place in the world and focus on that. There is no need to emphasize discussion of what the best Christian society would do, if there is not even consensus over the concept of one truth being good, let alone that of the Christians.
For now, we should nurture the things that we do have, which, as I hope this blog serves to illustrate, is more than a little.