The interview was conducted by Notre Dame philosopher Gary Gutting, and I encourage you to read the whole thing before making any definitive assessment of Plantinga's arguments because I can't do them justice here.
In response to a question from Gutting about whether many philosophers are atheists is because there's not enough evidence for belief, Plantinga replies that the lack of evidence, if such there be, only warrants agnosticism it doesn't justify atheism:
A.P.: In the British newspaper The Independent, the scientist Richard Dawkins was recently asked the following question: “If you died and arrived at the gates of heaven, what would you say to God to justify your lifelong atheism?” His response: “I’d quote Bertrand Russell: ‘Not enough evidence, God! Not enough evidence!’” But lack of evidence, if indeed evidence is lacking, is no grounds for atheism. No one thinks there is good evidence for the proposition that there are an even number of stars; but also, no one thinks the right conclusion to draw is that there are an uneven number of stars. The right conclusion would instead be agnosticism.Gutting observes that atheists often deny that they need evidence, insisting that all they need do to justify their lack of belief in God is point out the lack of any good evidence for theism:
In the same way, the failure of the theistic arguments, if indeed they do fail, might conceivably be good grounds for agnosticism, but not for atheism. Atheism, like even-star-ism, would presumably be the sort of belief you can hold rationally only if you have strong arguments or evidence.
G.G.: ...Atheists say (using an example from Bertrand Russell) that you should rather compare atheism to the denial that there’s a teapot in orbit around the sun. Why prefer your comparison to Russell’s?But what about the arguments that show that God doesn't, or probably doesn't, exist? Actually there are very few such arguments that amount to much. Only the "problem of evil" poses a significant defeater for belief in God. Plantinga addresses the argument:
A.P.: Russell’s idea, I take it, is we don’t really have any evidence against teapotism, but we don’t need any; the absence of evidence is evidence of absence, and is enough to support a-teapotism. We don’t need any positive evidence against it to be justified in a-teapotism; and perhaps the same is true of theism.
I disagree: Clearly we have a great deal of evidence against teapotism. For example, as far as we know, the only way a teapot could have gotten into orbit around the sun would be if some country with sufficiently developed space-shot capabilities had shot this pot into orbit. No country with such capabilities is sufficiently frivolous to waste its resources by trying to send a teapot into orbit.
Furthermore, if some country had done so, it would have been all over the news; we would certainly have heard about it. But we haven’t. And so on. There is plenty of evidence against teapotism. So if, à la Russell, theism is like teapotism, the atheist, to be justified, would (like the a-teapotist) have to have powerful evidence against theism.
A.P.: The so-called “problem of evil” would presumably be the strongest (and maybe the only) evidence against theism. It does indeed have some strength; it makes sense to think that the probability of theism, given the existence of all the suffering and evil our world contains, is fairly low. But of course there are also arguments for theism. Indeed, there are at least a couple of dozen good theistic arguments. So the atheist would have to try to synthesize and balance the probabilities. This isn’t at all easy to do, but it’s pretty obvious that the result wouldn’t anywhere nearly support straight-out atheism as opposed to agnosticism.Plantinga goes on to point out that he doesn't think that good arguments are necessary to justify belief in God, but that he believes that there are a couple of dozen good arguments for theism nonetheless.
A.P.: I should make clear first that I don’t think arguments are needed for rational belief in God. In this regard belief in God is like belief in other minds, or belief in the past. Belief in God is grounded in experience, or in the sensus divinitatis, John Calvin’s term for an inborn inclination to form beliefs about God in a wide variety of circumstances.One objection frequently introduced by skeptics is that in this modern age one can no longer believe in supernatural causes, but, as Plantinga shows, this is a rather flimsy objection to theism:
Nevertheless, I think there are a large number — maybe a couple of dozen — of pretty good theistic arguments. None is conclusive, but each, or at any rate the whole bunch taken together, is about as strong as philosophical arguments ordinarily get.
A.P.: Some atheists seem to think that a sufficient reason for atheism is the fact (as they say) that we no longer need God to explain natural phenomena — lightning and thunder for example. We now have science.One reason many philosophers are atheists is that they have an apriori commitment to materialism that precludes the existence of any non-physical entities in their ontology. The problem with this - and this is the gravamen of Plantinga's most recent book, Where the Conflict Really Lies - is that one cannot logically hold to both materialism and Darwinian evolution. Yet almost every materialist is a Darwinian:
As a justification of atheism, this is pretty lame. We no longer need the moon to explain or account for lunacy; it hardly follows that belief in the nonexistence of the moon (a-moonism?) is justified. A-moonism on this ground would be sensible only if the sole ground for belief in the existence of the moon was its explanatory power with respect to lunacy. (And even so, the justified attitude would be agnosticism with respect to the moon, not a-moonism.) The same thing goes with belief in God: Atheism on this sort of basis would be justified only if the explanatory power of theism were the only reason for belief in God. And even then, agnosticism would be the justified attitude, not atheism.
AP: Well, if there are only material entities, then atheism certainly follows. But there is a really serious problem for materialism: It can’t be sensibly believed, at least if, like most materialists, you also believe that humans are the product of evolution.But doesn't evolution select for accurate beliefs? Don't accurate beliefs enhance survival? Here's Plantinga:
[R]oughly, here’s why. First, if materialism is true, human beings, naturally enough, are material objects. Now what, from this point of view, would a belief be? My belief that Marcel Proust is more subtle that Louis L’Amour, for example? Presumably this belief would have to be a material structure in my brain, say a collection of neurons that sends electrical impulses to other such structures as well as to nerves and muscles, and receives electrical impulses from other structures.
But in addition to such neurophysiological properties, this structure, if it is a belief, would also have to have a content: It would have, say, to be the belief that Proust is more subtle than L’Amour.
But here’s the important point: It’s by virtue of its material, neurophysiological properties that a belief causes the action. It’s in virtue of those electrical signals sent via efferent nerves to the relevant muscles, that the belief about the beer in the fridge causes me to go to the fridge. It is not by virtue of the content (there is a beer in the fridge) the belief has.
[I]f this belief — this structure — had a totally different content (even, say, if it was a belief that there is no beer in the fridge) but had the same neurophysiological properties, it would still have caused that same action of going to the fridge. This means that the content of the belief isn’t a cause of the behavior. As far as causing the behavior goes, the content of the belief doesn’t matter.
Evolution will have resulted in our having beliefs that are adaptive; that is, beliefs that cause adaptive actions. But as we’ve seen, if materialism is true, the belief does not cause the adaptive action by way of its content: It causes that action by way of its neurophysiological properties. Hence it doesn’t matter what the content of the belief is, and it doesn’t matter whether that content is true or false. All that’s required is that the belief have the right neurophysiological properties. If it’s also true, that’s fine; but if false, that’s equally fine.I've only provided an adumbration of the interview here. Plantinga fleshes out his arguments more fully at the link.
Evolution will select for belief-producing processes that produce beliefs with adaptive neurophysiological properties, but not for belief-producing processes that produce true beliefs. Given materialism and evolution, any particular belief is as likely to be false as true.
GG: So your claim is that if materialism is true, evolution doesn’t lead to most of our beliefs being true.
AP: Right. In fact, given materialism and evolution, it follows that our belief-producing faculties are not reliable.....
So if you’re an atheist simply because you accept materialism, maintaining your atheism means you have to give up your belief that evolution is true. Another way to put it: The belief that both materialism and evolution are true is self-refuting. It shoots itself in the foot. Therefore it can’t rationally be held.
A closing thought: It appears that many of the commenters either didn't read the interview carefully or didn't understand Plantinga's arguments. They're much more sophisticated and formidable than some of the superficial dismissals of the commenters might lead one to believe.