(An original post by me for a change.)
For all the Catholic blog-verse's infatuation with Feser's work, in terms of his significance as a serious academic philosopher of religion Feser is pretty much nobody. The top dog in that particular kennel is generally considered to be Alvin Plantinga, who was just interviewed on the NYT's Opinionator blog by Gary Gutting under the title "Is Atheism Irrational?".
(No prizes for guessing Plantinga's answer to that one.)
Reading anything by Plantinga is always a somewhat odd experience. The puzzle is not his arguments—which are rarely more than the warmed-over corpses of long-dead apologetics—but the fact that people take them so seriously.
This interview is an excellent demonstration of the vacuity of his arguments. He starts off by claiming (in response to a question about the predominance of atheism amongst philosophers) that if arguments for theism fail then the rational position is agnosticism rather than atheism; but his argument to support this is a ludicrously poor analogy (given some large collection of objects, we should be agnostic as to whether there is an odd or even number).
This analogy might work if propositions like "X exists" and "X doesn't exist" started off on an equal footing. But they do not; we can conceive of a vast number of things that don't exist, while we rarely conceive of anything that does already exist without first seeing evidence. So in the absence of any evidence, we'd reasonably take a position closer to "X doesn't exist" rather than perfect agnosticism.
But then there's another issue: equivocating between "no evidence" in the sense of "we haven't looked at the evidence yet", and "no evidence" in the sense of "evidence we would expect to see is not found". In the second case, the "absence of evidence is evidence of absence" rule applies. Plantinga knows this, because he uses it himself in his second answer: he points out that we can disbelieve in Russell's Teapot because (so he says) it could only exist if someone on Earth had launched it, and we'd have heard about it if someone had. The applicability of this same argument to theism seems to escape him; there is a long list of things we'd expect to see or hear about if a theistic god existed, and we don't.
Plantinga also commits the basic mistake of confusing "argument" and "evidence". He concedes the problem of evil as possible evidence against theism, but then thinks that it could be countered by argument rather than just evidence.
Much of the rest of the interview covers two of Plantinga's most famous arguments:
1) That belief in god is "properly basic" because we have a reliable (hah!) sensus divinitatis, treating religious experience as though it were a sense perception (how this can be considered reliable when everyone gets a different result from it is not explained)
2) That evolution (or rather a biologically-ignorant philosopher's crazy strawman caricature of evolution) could not produce reliable belief-forming mechanisms.
I think the obvious conclusion from this is that modern academic philosophy, especially philosophy of religion, has clearly failed to produce any reliable belief-forming mechanisms.
