Dear Tim,
I agree with the warning, and appreciate it, but do they actually use numerology to challenge established doctrine? I'm not disputing it, but I've read a lot of Leithart and Jordan over the years and I'm not recalling a specific instance.
For the rest of it, there's certainly the chance of excess. And whatever specific techniques were or were not involved, the oatmeal-stout-FV has certainly established a smokescreen around what they really believe that has held for several years. That's not a clear sound, that's not a sound that consistently calls men to fight the good fight.
But there are places in the text where, for instance, we need to ask what "do not let your eye be evil" actually means. Or to notice a cascading (chiastic) structure, and to ask what it means (often that the center piece is related to the bookends, and is the focal point). Or to notice obvious parallels between two characters or events in the text (typology) and to ask what it means (often a compare/contrast). Shall we draw near to Sinai, or Zion? Shall we imitate the sons of Sarah, or the sons of Hagar? We need to know what that means. Why is baptism like the flood? And so on.
And this goes further into "reading" the story we're living in right now, though obviously we have to be more careful when we don't have an inspired word on both ends of the comparison.
These things aren't all that complicated. It doesn't take a terminal degree. It doesn't contradict the clarity (or "perspicacity", I think you've called it) of the text. Mostly it just requires paying careful attention to the text and remembering the broader context inside and outside the book. The closesr we are to "his blood is Bibline" (as Spurgeon said of Bunyan, I believe), the more we will see these connections and benefit by thinking about them.
And I'm sure you know far more about those things than I do. But I bring it up because I spent several years of my Christian life having no idea about these things in the text until I read Leithart's commentary on Samuel. I saw, as one of Jordan's book titles put it, "through new eyes". And as I read with those concepts in mind my belief in justification by faith wasn't subverted, but rather reinforced. Because God passed between the animals, and the Spirit was given as an earnest, I know Lutheran-FV is wrong.
Was FV the only way I could have learned those things? Certainly not. But I certainly wasn't getting it from my local PCA pastor, or John Piper's books, or any of the other branches of the church I spent time with. And one of the typologies of history is that when the church neglects something lawful and necessary, or overdoes something lawful in moderation, then movements will arise and find many converts because they aim to correct the neglect/excess. Some of those movements will be errant, even heretical.
So tell me, dear brother, are these things I've named part of the danger? If so, I want to know. If not, what specific methods are these men using that so set your teeth on edge?
Love,
Keith