The Gettier Problem and Relevant Alternatives Theory
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Suppose you're driving through rural Pennsylvania. As a matter of fact, the region you're driving through contains a lot of fake barns: mere wooden fronts that just look like barns from the road. But you don't know this, and have no reason to suspect it. You look off to your left and you see something that looks like a barn, so you believe "That's a barn." In fact, it is a barn. It's one of the few barns in the region. But you're just lucky. If you had looked at a fake barn instead, you would have believed that it was a barn.
In this case, it seems that your belief that you're driving by a barn is justified or reasonable. After all, it looks like a barn; and you've never heard about a region full of fake barns. And your belief is also true. But we're reluctant to say that you know that you're driving by a barn.
Cases of this sort are known as Gettier cases, after the philosopher Edmund
Gettier (1963). Before Gettier, philosophers thought that knowledge was equivalent
to justified true belief.
But then Gettier came along and presented examples in which the subject has a justified true belief which, intuitively, fails to count as knowledge. The fake barn case we just discussed is an example of that sort. (That particular example was created by Carl Ginet). Here's another Gettier case:
You have a justified belief that someone in your office owns a Ford. And as it happens it's true that someone in your office owns a Ford. However, your evidence for your belief all concerns Nogot, who as it turns out owns no Ford. Your belief that someone in the office owns a Ford is true because someone else in the office owns a Ford. Call this guy Haveit. Since all your evidence concerns Nogot and not Haveit, it seems, intuitively, that you don't know that someone in your office owns a Ford. So you don't know, even though you have a justified belief that someone owns a Ford, and, as it turns out, this belief happens to be true.
Gettier offered another counterexample as refutation. For our purposes an example adapted from Russell will serve to illustrate. Ed has worked in an office for forty years and has observed a clock working reliably that whole time. One morning Ed glances at the clock and as a result believes that it is nine o’clock. What he does not know is that the clock stopped precisely twelve hours previously. Thus it is true that it is nine o’clock, Ed believes that it is nine o’clock, and Ed is justified in his belief that it is nine o’clock. However, the intuition of most is that Ed does not know that it is nine o’clock. Something seems to be missing.
These cases are counter-examples to the claim that justified true belief is sufficient for knowledge.
The Gettier Problem is to state what, in addition to or instead of justified true belief, is needed to have knowledge.
Notice that the Gettier Problem only arises because we were trying to say that you could know that someone owns a Ford on the basis of evidence that falls short of certainty. If we instead said that knowledge requires infallible or absolutely certain evidence, then it would be clear why you're not in a position to know that someone owns a Ford. You don't have infallible evidence that someone owns a Ford.
This solution would do the trick. It would make our account of knowledge immune to Gettier-type counterexamples. But it would also make it next to impossible to have knowledge. So it seems like a bit of overkill. Most philosophers who have attacked the Gettier Problem have tried to find some solution which still allows subjects to know things on the basis of fallible, defeasible evidence.
One salient feature of the Nogot/Haveit Gettier case is that the reasoning that leads you to the belief that someone owns a Ford goes through a false step, namely the step where you believe that Nogot owns a Ford. So a possible solution to the Gettier Problem might be this: knowledge is justified true belief--where the reasoning your belief is based on doesn't proceed through any false steps.
Philosophers initially thought this was a promising solution. But unfortunately, Rich Feldman described Gettier-like cases where your reasoning doesn't proceed through any false steps, but intuitively you still don't count as knowing. So the present solution doesn't get to the root of the problem.
Feldman's case works like this:
You see Nogot waxing a Ford, humming Ford ad jingles to himself, and so on. On that basis, you conclude that someone in your office is waxing a Ford, humming Ford ad jingles, and so on. This belief is true. On the basis of that belief, you conclude that someone in your office owns a Ford. As before, Haveit owns a Ford so this belief is true.
Once again it seems like you have a justified true belief that someone owns a Ford, which fails to count as knowledge. In this case it does not look like your reasoning proceeded through any false steps.
Another kind of Gettier case where you don't seem to reason through any false steps is discussed in the Rosenberg dialogue:
You're in the meadow, and you see a rock which looks to you like a sheep. So you say to yourself "There's a sheep in the meadow." In fact there is a sheep in the meadow (behind the rock, where you can't see it).
Here again you have a justified true belief that there is a sheep in the meadow, which fails to count as knowledge. In this case, your belief doesn't seem to be based on any reasoning at all. (You could argue the same for the original example with the barn, too.)
Another popular solution to the Gettier Problem is to say that you know that P iff you have a justified true belief that P, and there's no true information "out there" in the world that would defeat your justification for P, were you to learn of it.
As you can see, it's very difficult to say what we need to add to justified true belief, to turn it into knowledge.
A philosopher named Dretske is a fan of the Relevant Alternatives Theory. For example, you're at the zoo, and in the pen in front of you is a striped horse-like animal. The sign on the pen says "Zebra." Do you know that the animal is a zebra? (Assume that in fact it is a zebra.) Dretske says: Well, what about the possibility that it's just a mule painted to look like a zebra? Do you really know that the animal is not a cleverly-disguised mule? You may have some reason to believe that it's not a cleverly-disguised mule. (Zoos don't typically try to fool people like that.) But your evidence doesn't seem to be good enough to know that it's not a cleverly-disguised mule. You haven't made any special tests, or anything like that. So Dretske thinks you don't know it. But he still wants to say that, so long as the mule hypothesis is not a relevant alternative, you can know that the animal in the pen is a zebra.
Now the important question is: What determines when a possibility counts as "relevant"? Does the subject have to know about the painted-mule possibility, for it to be relevant? Dretske doesn't think so. He thinks alternatives can be relevant for you, and can keep you from having knowledge, even when you haven't come across any evidence that they're true. Perhaps it's enough if there's some suspicious zoologist poking around in the neighborhood, who does have evidence there are painted mules in the area.
Let's look at another case: Suppose Norman is a reliable clairvoyant but doesn't know it. One day, Norman forms the belief that a certain horse will win a race (which turns out to be true). However, Norman has no evidence whatever indicating that he is clairvoyant. Nor has he any way of recognizing that his belief was caused by his clairvoyance. Norman, then, cannot recognize that his belief is justified. Does he have knowledge?
Internalists and externalists assign different roles to justification, what they ultimately disagree about is not the nature of justification, but knowledge. Internalists assign justification the role of turning true and degettiered belief into knowledge because they take internal justification to be necessary for knowledge. In contrast, externalists assign a different role -- that of turning true belief into knowledge -- to justification because they think that internal justification is not necessary for knowledge. It is this difference in their respective views on the nature of knowledge that leads to different views on the nature of justification.
Mostly from:
James Pryor, Princeton University
http://www.princeton.edu/~jimpryor/courses/epist/notes/gettier.html
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