Continuing my series about the Pedantic Protestant's comments on Catholic apologetics, we come to Prong 3, the a priori arguments for Catholicism. I would argue that most of the arguments that the PP cited are not, in fact, a priori in any respect. At the very least, they are not a priori premises any more than any of the ordinary standards of reasonableness. Once again, the PP has been conscientious to provide an explanation, which notes that the Catholic premises are quite natural, stemming from a quest for absolute certainty [instead of epistemic probability]. But I will argue that this misreads the basis of the Catholic position (not without ascribing some blame to Catholics who misrepresent the argument from time to time).
To begin with, any argument for infallibility based on absolute epistemic certainty is absurd on its face. Grounding an infallibility claim based on the epistemic content of one's own head requires one to claim infallibility in one's own perception, which essentially requires omniscience. Consequently, the argument "we need an infallible interpreter to be certain of X" is absurd, whether it takes the form "we need an infallible interpreter for Scripture to be certain of its meaning" (the Catholic version) or the equally-absurd argument that the meaning of Scripture must be perspicuous by application of the grammatical-historical method in order for Scripture to serve as an instrument of truth (made here by a Baptist apologist). [As an aside, the latter argument is entirely alien to the claritas Scripturae principle of the Reformation, so one oughtn't take my position here as a general attack on Protestantism or sola Scriptura, but rather as a critique of bad arguments for anyone's position.] Clearly, bad arguments are made on both sides, but I think that non-Catholic opponents often mistake an argument about "certainty" in the probabilistic sense with "certainty" in the absolute sense.
I would argue that we are beginning from the same position a priori; namely, that one ought not accept truth as coming from the revelation of Christ unless one has sufficient evidential reason for doing so. Note that I'm assuming that one has already done sufficient evidential work in concluding that God exists, that Jesus existed, that He was actually raised from the dead, that there are other documented miracles associated with Jesus's life to provide reasonable documentation that this case (unlike other religious claims) is not woven from whole cloth, etc. Here, the presuppositionalists will depart, squawking about the need to "accept the revelation of God by faith as the only possible ground of truth," and I will cheerfully say "Don't let the door hit you on the way out!" I say that because I think the real difference of Christianity is that it IS grounded in history and particularity, and that salvation by grace alone encompasses that fact, rather than attempting to "transcend" it as virtually all other religions do in some way.
So we've got to the point where we say "I'm reasonably certain that this Jesus fellow had enough truly miraculous events in His life that the documentation of His claims to be the Son of God are probably accurate, and moreover, those claims are probably true." The evidential question then becomes "How can I be reasonably certain that what I believe is accurately connected to this historical event of revelation?" (or to put it another way, "What are sufficiently reasonable grounds for supposing that the meaning intended by God in Christ's life corresponds to the belief that I hold?"). That evidential framework is what causes us to use the terms "infallible" or "inerrant" or "rule of faith." Contra the presupps (as well as people who make arguments from absolute epistemic certainty, incidentally), those aren't a priori determinations that we make from which our subsequent beliefs about evidence are formed, and they aren't rational preconditions for truth. Instead, they are evidential determinations formed from our experiences according to our beliefs about evidence. In other words, infallibility is a conclusion, not an assumption from which all other sure beliefs must be formed. The conclusion of infallibility is no more certain than any other question. Since everyone is fallible, it's strictly a question of the object of submission (viz., to whom or to what you submit your will or judgment). [BTW, that's also useful to explain the Catholic term "private judgment," which refers to the refusal to submit one's will or judgment in accountability to any other person or people.]
Unfortunately, because so many people are enamored with the easy temptation of presuppositional arguments, no one gets into the monstrously difficult evidential question involved in establishing the realibility of one's epistemological system. That's where all of those difficult factual judgments on the historical record, and I have yet to see any explanation that was even decent in comprehensively covering the issue, much less describing how one values things like linguistic probability and historical evidence relative to one another. And even that difference probably relates to different opinions on things like what type of evidence is more reliable, how efficient one expects the information transfer to be, what form one expects the information to take, etc., etc. Every one of the PP's six examples of a priori reasons devolves to one of these weighting factors or judgments; none is an absolute principle held as absolutely inviolable in the face of compelling evidence. The most palpable evidential difference I can think of between Protestants and Catholics is whether the true meaning of Scripture inspired by God is isomorphic with the meaning most likely intended by the inspired authors (Catholics would say no; most Protestants would presumably say yes).
The problem is that these issues are often discussed in an apologetic context in which both sides are entirely inarticulate in explaining them. There is a strong incentive to "cover" those areas in which one honestly has faced doubts and to be insufficiently critical of one's own case, and as a result, the appearance is that people have not even considered the counter-evidence (which is, in my experience, hardly ever the case). A Protestant might consider a "debate" over if he shows that an intepretation is not the most probable from Scripture, while a Catholic views that as the starting point of a multi-factor analysis, so they're effectively speaking two entirely different languages. Neither has "proved" a thing to the other, because they are too far apart on what proof is to communicate. I don't have a problem with debates per se, but the topics aren't being picked in such a way that people can avoid talking past each other. And of course, presuppositional apologetics don't help a thing.
Anyway, there's simply too much failure to give credit to the other side for being reasonable (and conversely, to admit when one's own argument is less than convincing to one's opponent and to recognize why). Doesn't mean namby-pamby, "everybody's right" postmodernism or liberalism, but it does mean recognizing the finitude of human methods of acquiring knowledge and being able to know when you're guessing to fill in the gaps rather than simply assimilating factual evidence. So that's my turn on the soapbox. Apologies to the Pedantic Protestant in case I have provoked a "What did I do to deserve this bloviating in my direction?" But I really did think that the PP's explanation was a very helpful framework for covering these issues, even if the PP was shooting from the hip.