Every car I've ever driven has a blind spot. They're just in slightly different places in each car, depending on how the car's frame is built. Every framework has a blind spot because the framework itself creates the blind spot. You can't see through the sides of the support structures; you have to look at what the framework itself hides from view. The side mirrors help. But even the side mirrors don't catch everything. You actually have to turn your head and look.
When I was training my son to drive, we did an exercise: watch a car that's in the next lane that's moving slightly faster. Watch it in your rearview mirror as long as you can. Watch it come closer, and watch it in your side mirror as long as you can. When you can't see it in your side mirror any longer, notice the gap between the time it disappears from your side mirror and the time you can see it out your driver's side window. There really is a blind spot. You know it because there are things that disappear, and places around your car where that happens every time.
So how do you find a blind spot in your theology? We have to ask ourselves, "What kinds of things would be impossible to see in a certain framework?" And, "If we look for them, do those things exist?"
Case study: Lutheran theology
Let me start with a blind spot of Lutheran theology, so I critique my own rather than someone else's theology. I want to make clear from the outset that noticing a blind spot is not attacking the theology. Lutheran theology is good at many things. It's been a notable influence on those outside the Lutheran tradition. John Wesley's famous Aldersgate experience happened "where one was reading Luther's preface to the Epistle to the Romans" in Wesley's words; it is "200-proof grace" as the Episcopal theologian R.F. Capon has put it. So I am not bashing Lutheran theology as bad, but showing that even with something known to help, there are still blind spots.
One framework Lutherans find very helpful is known by the shorthand name, "Law and Gospel." Basic background, just a rough sketch: "Law" covers anything God commands us or demands from us, and the destruction of evil that the law promises. "Gospel" is anything that shows the goodness and faithfulness of God, though especially Christ in his death and resurrection for the forgiveness of our sins.
For all the help that this gives us understanding things, some things still just don't fit. What if God asked us to do something, not as a demand of the law under threat of condemnation, but as an act of love for his goodness, a joyful participation in his redemption of the world? "Law v. Gospel" doesn't really have a place for what God asks us except under the "Law" side of the equation. Things on the "Law" side are seen as curbing sin, or awakening us to the reality of our sinfulness, or even instructing us in godly living. But an excess of anything in the "Law" category is seen as a type of legalism. Anyone familiar with Christian circles -- or any religious circles -- knows just how easily the zeal for good turns into legalism and one-upmanship.
The problem? There is not an equally recognized place in Lutheran theology for works that do not fall under the law. Maybe that's why our hymnals include St. Francis' prayer: "Lord, make me an instrument of your peace." We sense that there is an area we haven't really addressed in systematic theology, at least not adequately, but is a legitimate part of following Jesus. Being instruments of God's peace does not fit easily under law or gospel as usually discussed, but it is a reality to which we are called. It is a blind spot of Lutheran theology.
Case study #2
I was going to trace out somebody else's theology, but I'd rather invite you to look at your own.
I have previously spoken of a few tests for blind spots in theological systems. There was the Bible Playoff test: if we split the verses of Scripture into teams and see which group wins, then we have a blind spot where the losing verses got clobbered. There was the Leftover Parts test: if you take apart anything, then put it back together and have extra parts left over, then you probably didn't really know what they were for. You can rest assured that the omitted verses are in a theological blind spot of the system involved.
I think we should start with the recognition that every interpretive framework has blind spots. By definition, if we focus on one thing then we are not focusing on another thing. Unless we are focusing on the big picture we will lose sight of it. I mentioned previously why I think, in Christian theology, the big picture is Christ. If we are focusing on Christ, we have the big picture; if not, beware of blind spots. The biggest blind spot will be losing sight of Christ. Who, then, are we following?
Beyond that, the blind spots change by what kind of framework we have. If a framework insists that we classify things into a certain number of pre-defined categories, then odds are that not everything truly fits and that will become a blind spot. If a framework insists on seeing God with a certain attribute first and foremost at all times, all the times when God does not choose that particular attribute first and foremost will become a blind spot. If a framework is part of a polarized argument between warring camps generally thought of as "us" and "them," it is very likely that there are multiple blind spots. The first casualties of polemics are usually humility and love of neighbor, and in Christian theology in particular that does amount to a blind spot as it means we have in fact lost sight of Christ. It is also likely that there is somewhere a kernel of truth in each camp, and that the other side is trying very hard to ignore it -- which guarantees the creation of a blind spot. If we cannot understand what our opponents' objections are, we probably have a blind spot. I do not mean that each person should think that everyone who takes up an argument against him is right at every point; I mean that if we cannot state our opponents' objections fairly, we don't really understand it. And if we don't really understand it, that is by definition a blind spot.
Who, then, are we following?