One of the really valuable elements of the theological turn in the resurgent Calvinist movement is the application of the theological implications of the gospel in preaching. I take it that the point of preaching on this view is a sort of interpretive conditioning for the congregant, aimed at helping one to see reality rightly. The Spirit works through the gospel to convince me of the truth about who I am, what Christ is for me, and what I am in him. This sort of rehearsal of the implications of the gospel is really significant for everyday life because these truths form the background for how we perceive mundane realities from struggles at work to dealing with children (it deals with our hearts).
And yet, I have a growing concern about truncating application to theological implications, namely, that it truncates biblical authority to the general orientation of the Christian mind. If preaching mostly pertains to theological generalities, there are a whole host of significant issues that have no place for being considered theologically in the church. Issues like global politics, economics, education, psychology, or even technology have no possibility of being addressed with theological nuance because there is no platform for talking about them. Thus, practically, the Bible’s authority does not extend to them.
I think the worry from preachers is that one does not preach on “economics” because to do so is to step too far into the theological debatable or speculative. Without commenting on the merit of this argument for preaching, it is at least worth noting that this avoidance of the debatable or speculative has the practical effect of fostering terrible thinking about these issues in the church.