I actually wrote “Is it rational to believe random stuff for no good reason?“, or 80% of it anyway, twice; WordPress whimsically threw away the first version.
In the second version there, I left out one argument that I discussed the first time. Between saying that he doesn’t believe in God by choice, and saying that the atheological evidentialist objector may regard the theist-without-evidence as sick or malfunctioning, Plantinga argues that there is not a general obligation to have evidence for everything you believe, thus:
[T]here seems no reason to think that I have such an obligation. Clearly I am not under an obligation to have evidence for everything I believe; that would not be possible. But why, then, suppose that I have an obligation to accept belief in God only if I accept other propositions which serve as evidence for it?
Well, he’s not so much arguing as he is baldly asserting, with a “clearly” in there for emphasis. But we can think about what he might mean by it.
I can think of three things he might be saying here.
First, he might be pointing out that I’m not obliged to have prepared in advance evidence for everything that I believe. That would be an awful lot of stuff to carry around with one just in case, so to speak, either physically or cognitively. And that’s fine, it seems reasonable to state the requirement of rationality that one should be able to produce good reasons for one’s beliefs, if asked, not so much that one should be aware of those reasons at all times.
Second, he might be making a sort of foundational or preconditional argument, saying that we can’t have evidence for stuff that is so basic to thinking itself that it’s really a precondition for anything even counting as evidence. Things like the reality of the past (as opposed to the world having sprung into being ready-made ten seconds ago), not being a brain in a vat, etc. You can’t really have evidence for them (or against them) since ex hypothesi they are entirely consistent with all of our experiences.
And this is reasonable also. It means that we can’t demand that all beliefs are based on sufficient evidence, and I think the right rationalist response to that is to say that all beliefs should be based on good reasons, where reasons are a superset of evidence, and also include things being preconditions for thought or evidence itself. Someone may someday come up with a system where we can do rational discourse without presupposing the reality of the past or our own nonvatness, but until that happens we have good reason to believe them, just because otherwise you’re dead in the water.
Third, he might just mean “there’s no reason to require that anyone have any reason for believing anything”, but since interpreted one way that’s just asserting as obvious the whole conclusion that the paper is aiming at (which would be silly), and interpreted another way it’s just weird (of course rationality requires something of our cognitive behavior, or it has no content at all), I will assume that he doesn’t mean that.
So we can take this argument to be pointing out that rationality doesn’t require us to, at all times, have in mind evidence for everything that we believe, but rather that it requires that we can, if asked, produce good reasons for believing each thing that we believe, where reasons are broader than just evidence.
This doesn’t actually work very well as as argument for what he wants to argue, though, since he seems to want to say not just that it’s okay to believe in God even if you don’t have sufficient evidence on the tip of your tongue, but also that it’s okay to believe in God for no good reason at all. And that’s far too strong a proposition to demonstrate by mere assertion.
While I’m here saying more stuff about this Plantinga paper, I’d also like to note not only how he slips from talking about believing in God for reasons into talking about believing in God simpliciter, but also how he conflates theism in general with his particular Christian theism.
Here’s a passage that especially raised my eyebrows:
[The theist] will see the atheist as somehow the victim of sin in the world — his own sin or the sin of others. According to the book of Romans, unbelief is a result of sin; it originates in an effort to “suppress the truth in unrighteousness.”
Of course not all theists have any particular theory about “sin”, or about the causes of unbelief, or about Romans (bookish or otherwise); last I looked, most theists weren’t Christian at all. Again, despite the putative topic of the paper, Plantinga doesn’t seem to be interested in a general philosophical point about the rationality of believing in God without evidence; really he’s just launching a salvo in the defense of Christianity. I’d have more respect for him if he’d just do that, and not pretend to be doing something else…