Coffey was very annoyed with my essay this term for betraying what he thought was an unexamined presupposition underlying my work--that I "attach to the word 'historical' (and to terms like 'evidence') a positivistic content that renders it unusable for theology." And I thought that I'd been arguing against positivism throughout Marxsen's work. Arg. There's nothing like an accusation of an unexamined presupposition to really rankle when you think you've really examined and guarded against such things for years.
So, after conversations with a wide variety of folks and lots of reading about positivism and critical philosophy of history today at the library, the best understanding I've been able to come up with was that a focus on the evidentiary value of historical arguments represents an equal capitulation on my part to a positivism, and to its latent empiricism or rationalism. And if that's what Coffey is getting at--yeah, I hadn't considered that as a possibility at all.
But if so, does that mean that "history" as a means of knowledge or a road to some knowledge of truth is then surrendered to Enlightenment philosophy and its prejudices against Christianity? That's what I seem to find myself resisting: I would think that that result has to be part of a "faith vs. reason" false dichotomy that I want to reject: fideism or positivism. I recognize easily enough that there are areas properly "theological" where history as a science cannot go, but it seems to me that history can certainly go some distance until it runs up against that boundary.
My other conclusion is that trying to dig up your presuppositions--even after being aware of the need, and trying to practice it, for over a decade--is worse than trying to go after dandelion roots.