One may be justified in believing that p even if p is false. This opens the door to Gettier cases, no matter how stingy or generous the criteria are. The problems actually arise when S believes the right thing for the wrong, but justifiable, reasons.
How to respond? Well, my response to your farmer is 1) he thought he saw a cow, 2) he didn’t see a cow, 3) there was a cow. I observe that a) 1) and 3) are reasons for saying that he knew and that b) 2) is a reason for saying that he didn’t. I conclude that it is not proven that he knew, and that it is not proven that he didn’t, so I classify the case as unclassifiable. — Ludwig V
I'll tell you what I think is the obvious thing to say here: the problem with the farmer's belief that there's a cow in the field is that it was not caused by seeing any of the cows in the field. Or: there was no causal connection between the farmer and a cow that contributed to the farmer's belief.
This is more or less a typical Gettier case because the conclusion is an existential claim that is true in virtue of the existence of some particular: it is true that there is a cow in the field because this particular cow, let's call her Alice, is in the field. In a sense, we don't even have to talk about what's wrong with a cow-belief being caused by a bit of cloth, about whether the interpretation of blurry light spots is a reliable method of cow detection; all we have to say is that the farmer has what looks to be a belief about Alice despite that belief not being causally connected to Alice.
This was more or less Alvin Goldman's response to Gettier, and it does seem to get something right. (Only just started looking at Goldman, so don't ask me about his views.)
My way of putting this raises some issues though: in what sense is the farmer's belief about Alice? This doesn't look good at all. Since Alice played no role in the farmer's belief formation, it's pretty clear Alice is no part of the content of the farmer's belief. Alice does play a part in the existential claim; Alice is what makes that claim true.
We can get to Alice, as a matter of content, with the obvious counterfactual claim: had the farmer seen Alice instead of the bit of cloth, and seen that Alice is a cow, then in that case he would of course know that there was a cow in the field. But he might have seen Alice and mistaken Alice for a bit of cloth flapping in the breeze — so not seen
that Alice is a cow — and formed the mistaken belief that there's a bit of cloth in the field, which might also be Gettierly true. That's a little uncomfortable for the causal account, as it stands so far, because it's just requiring the seeing itself to be a factive mental state. But at least now Alice, under some interpretation, is part of the content of the farmer's belief.
And that seems a reasonable starting point: Alice ought to play a causal role in beliefs about Alice. I don't think there is a remaining problem with the existential generalization after all because we can just enumerate it: if Alice, Bobbie, Clarabelle, and Dixie are the cows in the field, then the truth of such an existential claim as we're concerned with is a truth about at least one of those: one of those four ought to play a causal role in the farmer's belief, expressed as an existential generality.
Are we any better off though? Suppose the farmer thinks the cow he's seeing is Clarabelle, when it's Alice, even though Clarabelle is out there in the dark. There is some lingering oddness about the existential generalization; it feels a little unreal, like the content of his belief still involves Clarabelle, though expressed with reference to "a cow", and so his basis for believing that the generalization is warranted is suspect.
There are obvious cases in which the farmer would reach for the general, disjunctive claim because he sees a cow and doesn't know which one. What about in this case, where he believes he does know which cow makes the disjunction true? Now that's a funny thing, because it's very natural to have different degrees of confidence here: I for sure saw a cow, and I'm pretty sure it was Clarabelle — if it wasn't Clarabelle, I assume it was Alice or Bobbie or Dixie. That last clause can fail if a neighbor's cow has gotten into his field, but even that won't affect his high level of confidence that he saw a cow, some cow. We might even plump for him knowing it was a cow, while denying that he knows which one.
And that's a reminder that you absolutely can know a disjunction is true without knowing that one of the disjuncts is true. The law of the excluded middle is a clear enough example, but we might forget in these more mundane, probabilistic cases.
The farmer, then, could be in a state of disjunctive knowledge, connected causally to some truth-making cow, the actual content of which is a belief he holds only partially and could even be wrong about. (Something still weird about that formulation.)
In the original version of the story, it's a bit of cloth that is causally related to the farmer's implicitly disjunctive belief and another disjunct is true. What's different here from the case above where one cow is mistaken for another — and so there's acceptable disjunctive knowledge — is that you cannot see
that a bit of cloth is a cow, because it isn't. We are relying on the seeing being factive, and that's already expressed as predication; what causation gives us is an explanation for the acceptability of the predication: you can see that something is a cow only if it is a cow. Which I hope is another way of saying that some cow ought to be causally involved in your formation of cow beliefs.
@creativesoul, I think some of your concerns are addressed above.
@Andrew M, any thoughts?