Eph. 4:17-18: "So this I say, and affirm together with the Lord, that you walk no longer just as the Gentiles also walk, in the futility of their mind, being darkened in their understanding, excluded from the life of God because of the ignorance that is in them, because of the hardness of their heart."
At least in this passage, futility of mind, darkened understanding, and ignorance that makes it impossible to participate in the life of God all stem not from stupidity or lack of convincing arguments, but from hard hearts. Just ask Pharaoh how difficult it is to change your course of action towards God when you heart is hardened against Him.
But then, there are always means by which God accomplishes His ends. Isn't it possible that rational arguments are God's means at least sometimes of bringing people out of their ignorance?
Or take the more familiar example of Rom. 1:19-20: "...because that which is known about God is evident within them; for God made it evident to them. For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that they are without excuse." Here is a verse often quoted in support of apologetics because it seems to so obviously point to the intended efficacy of natural revelation.
But then, the whole point of Rom. 1:18-32 is that all humanity alike has sinned and faces the wrath of God. Put another way, despite all the natural revelation in the world (literally), no one gets the point! V. 18 says that men "suppress the truth in unrighteousness" (not "unknowingness"). The condition of man's heart is the problem, which means that the condition of man's mind isn't- or at least not fundamentally.
Paul in Athens in Acts 17 doesn't really help either no matter how often it is quoted in defense of apologetics. Sure, it does support the need to contextualize, but Paul ends up going to the resurrection as the witness of who God really is, not to natural theology.
But then, while it is easy for we theo-nerds to blog about the uselessness of apologetics, what do we say when we're sharing the gospel with someone who gives us their reasons why God cannot exist to begin with, or why Jesus most certainly was not raised from the dead? "I'd tell you why you're wrong about that, friend, but as the infallible Dr. Barth has blessedly taught us, it would do you no good. You need a good dose of special revelation, and until you get it, I cannot help you." Somehow I doubt that would help.
So what is the solution? Frankly, I don't know. On the one hand, I know that all the arguments in the world do nothing for a hard heart. On the other, I know that God does not typically zap people with heart change totally outside of life circumstances, whether they be emotional, moral, intellectual, or otherwise.
And this, dear reader, is why I write this post: to ask you to guide me. I know other CiC writers have wrestled with this as well, and I suspect that they will not only have helpful comments, but that they too will appreciate your input.