I've been doing some thinking about Reformed Epistemology and related topics, and there are a few things which I think are off with it, especially within Plantinga's scheme. Maybe this post could have been "Musings on the Faults of Warranted and Proper Function" as well. At any rate, I'm not sure that I have any R.E's on this blog, so maybe I'm just preaching to the choir; but let me know whether you think the following points are worth anything. It's been a while since I've read Plantinga or Wolterstorff, so maybe I'm off on exegesis as well as philosophy.
(1) RE wants to make out the "sensus divinatis" as a correlate of the sense perception. But sense perception doesn't give us concepts directly; we don't see "blue", we see light of certain wavelengths which we organize into the category blue. Russians, by contrast, organize the same wavelengths into синии, dark blue, and голубой, light blue. So, there is something we perceive which is subsequently shaped.
What is it that is perceived in the case of God? There's an awful lot of baggage brought into the notion of God; do we really perceive such a complex notion as REers seem to want to hold? Plantinga's God certainly isn't the simple God of the Neo-Platonists; the latter might be a better option for perception, but then would be different from what most believers hold (and so the sensus divinatis wouldn't do the work it is supposed to).
Therefore, for RE to work, the concept "God" must be something hardwired into our brains, and not perceived like with the senses; or else perceived in a very different way. If the former, then what is this unchanging concept which would need to exist across cultures? Whatever it is, it would again not look too much like the common God of the American conservative church, or of modern analytic philosophy. If the latter, we need much more explanation of the mechanics of the situation (or at least possible mechanics) in order for it to avoid being ad hoc.
This latter point seems to be the Great Pumpkin objection revisited. But here's where I think that it works: the "Great Pumpkin" is illegitimate as an object of some sensus pumpkinatis because people don't claim to know about such; people do claim to know God. But, what if "God" is a hopelessly equivocal term amongst communities? If "God" is a complex perception, then this perception would have the possibility of changing over cultures, which empirically is the case. So, not as many people would know "God" as would initially seem to be the situation, and the answer of RE becomes at least more ad hoc then we would like.
So, in sum, perception of God through the sensus divinatis is either a simple perception, a complex perception, or a hardwired concept. Simple perceptions are unlike anything the average American, Evangelical or Reformed (and often lay or educated) believer believes. Hardwired concepts are hard to fit with religious pluralism. Complex perceptions are ad hoc and need further explanation, as we have nothing else like them.
At this point, I would most likely encounter the Sin objection: there would be a unified concept of God, if it weren't for the fact that our sensus divinatis were "blinded" and must be regenerated, at which point sin would still mar our conception. I guess I can't really argue against that; it's hard to defend oneself against a position which says that one is wrong by default and without any recourse. But at least my argument should show how different the sensus divinatis is from other faculties.
(2) There is this notion in Plantinga's epistemology that when I see something blue, it must really be blue in itself or my faculties are not functioning properly. But what do I care about this? All I care about is that my perceptions are coherent, within themselves and when matched up with those of other person. Since I myself am not stuck in an epistemic loop with eagles and rocks (and I am not sure that such a case could occur in the actual world to a person whom we would still consider to be a rational agent), all I need to do is to be able to group like things together, differentiate different things, and further produce approximately the same groupings as other people. Whether the qualitative property of blueness exists either in another person's eyesight as in mine, or in some unfathomable way in the futon at which I am looking, is irrelevant and does not come into play in our concept formation or use.
But if this is the case, then Plantinga's argument against naturalistic evolution looks very shaky. First, as with the first point above, the idea that we all of a sudden get odd concepts (like that we should run a footrace with sabre-tooth tigers) is almost nonsensical; maybe it is logically possible, but why think (especially on an evolutionist scheme) that we get concepts out of the blue? They come largely from experience (at least, anything which an adult knows that a baby does not comes from experience, whether or not there are hard-wired concepts), and this experience is not piecemeal. Like situations are grouped together and unlike divided; there are no merely ad hoc concepts, as every one affects others by its similarity or dissimilarity. This is a very useful survival mechanism: if I see a fire, feel its heat, and burn myself, and then go over to another fire and repeat because I cannot tell that it is similar to the other case, I will not live very long. One has to reach a very high level of complexity before one could get even approximate particular stand-alone ideas, and by that time one would have had to have developed some sort of proper response to sabre-toothes.
But if this is the case, the at very least naturalistic evolution can explain our practical behavior. And if theory comes out of practice and refers back to it, then the stability of practical understanding would grant some stability to theoretical. So, the naturalistic evolutionist has grounds for thinking that her reason can discover something about the world.
If concept formation does come from such practical similarities and dissimilarities (and the vast majority of Western philosophy has held that concept formation begins with working through experiential input), we come back to the problem of the sensus divinatis; if the concept "God" is anything like "I should run a footrace with a sabretooth", then I have grounds for rejecting such a concept thrown into my skull from who-knows-where, without regard to typical causal mechanisms. We simply do not form concepts like that in any other circumstance, but only through a process which must be explicated. If "God"-concept-formation is something different, then what is it?