Thursday, December 09, 2004

Gettier cases via Skepticism

Editorial comment: I just rediscovered an old note I wrote back in early April. I must have forgotten to post it on the blog. So here goes...

Knowledge has traditionally been analyzed as justified true belief (the "JTB" analysis). That is, S knows that p if and only if:
  • p is true
  • S believes that p
  • S's belief-that-p is justified

Despite being initially plausible, there are a class of counter-examples (known as "Gettier cases") which cast doubt on this analysis. The scenarios they describe satisfy all three conditions, yet leave us reluctant to ascribe knowledge to S. The identifying feature of a Gettier case is that the justification involved, though usually acceptable, in this case turns out to be corrupted somehow - so that it is merely a matter of luck that p turns out to be true.

The example our lecturer gave involved a man driving down a road. He sees a cowshed, and so (justifiably enough) forms the belief "there is a cowshed". And it happens to be true. However, unbeknownst to the driver, life-like facades have been put up all along that road. In fact, of the 100 "cowsheds" along that road, this one is the only real one. So surely he doesn't really know he's looking at a real cowshed after all?

Interestingly, our class' intuitions were split pretty evenly on that example. A great many people weren't convinced. But after the lecture, I was talking to a friend about Skepticism, and we unwittingly came up with the following Gettier case, which I think is much more convincing:

Suppose you see a tree nearby, and so (justifiably) form the belief "I am located within ten metres of a tree". But it turns out that you're really a brain in a vat (or dreaming, or in the Matrix, whatever...). However, by sheer chance, your vat happens to be positioned against the wall of the Brain-Vat Storage Warehouse, and there is a tree growing outside (within ten metres of your vat). So you have a justified, true belief. But I suspect most of us would be disinclined to say that you really know there is a tree nearby.

12 comments:

  1. maybe you need a aditional thing saying that the statement P must be specific. for example "I am within 10 meters of THIS tree" solves the problem (mostly).
    the brodest problem is somthing like your matrix because in a sense it denies the possibility of true knowledge - and some philosophers would indeed say that was impossible.
     

    Posted by GeniusNZ

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  2. Ah, I think you've misunderstood my intent here. I want to create a Gettier case, not make one go away. I don't want to "solve" the problem. The alteration you suggest indeed would no longer be a Gettier case. But then, most cases aren't Gettier cases, so it's not very interesting to go and make another one that's also not. (As a general rule, you cannot respond to a counterexample by citing a normal, non-counter, example. Those mean nothing, whereas a single counterexample is sufficient to (dis)prove the point.)

    Perhaps you were suggesting that the scenario I present is not a genuine Gettier case, because the belief is not specific enough. But that doesn't make sense, because there's no requirement that beliefs be perfectly specific. One can just as well believe "someone is mortal" as "Socrates is mortal". The former is no less a genuine proposition (capable of being believed) than the latter.

    So there's no reason to disallow the belief of: "I am located within 10 metres of *a* tree", merely because of its generality. But we find the belief to be both justified and true, and yet not knowledge. So it stands as a counterexample to the JTB analysis.

    To clarify: my aim in the post was to present a Gettier case that might strike people as more convincing than the usual ones. (Plus it's just kind of fun to talk about brains in vats!)

    But I don't (here) intend the BIV example to cast doubt on "true knowledge". You can follow my 'skepticism' link for more details on that particular debate. You'll notice, for example, that I assume our agent is justified in believing their senses. A skeptic would deny that. 

    Posted by Richard

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  3. I for one think that the case stands--but only if you destroy the entire world, effectively, to save it.

    Here's one:

    "I believe I have syphillis." I've just injected myself with a sample of live syphillis culture. But really I got the disease years ago from a prostitute. (This is all strictly hypothetical, of course.) My belief is true, and justified, and yet I don't think one can say that I have knowledge of my illness.

    Perhaps we would have to reformulate JTB as follows: Knowledge is a contextually justified true belief. But then, this may well beg the question.
     

    Posted by Jason Kuznicki

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  4. haha I am a classic guy - give me a problem and I will try to solve it ;) (thinking of the "men are from mars" book)

    another idea - your examples like the matrix one rely upon a lack of information ie the person in question is NOT justified in assuming there is a tree 10 meters away, he has incorect information. He might as well be guessing entirely that there is a tree there since that would be almost as valid a deduction because he is ignoring vital pieces of information.

    Here is an example to keep you happy - imagine a tree ant that cannot distinguish between objects but for some reason knows what a tree is in its head (maybe evolution put it there)- that ant may be placed in a new environment and recognise a computer as a tree - that view is jsutified regarding its current level of information (it does not know how many trees there are it just knows there is at least one - ie they exist) but not so from our point of view.

    Still now I'll change tack - what if your examples ARE knowledge. that is that it doesnt matter why you believe somthing is true if you believe it is true and it is then that is sufficient? Ie you know there is a tree 10 meters from you then there is in a sence the thing you would call a tree the "distance" of 10 "meters" from you.

    so many ways to approach it ! 

    Posted by GeniusNZ

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  5. This may be off topic, but is it valid to use the word "know" in talking about how people once KNEW something that we now know to be false, such as the world's being flat or early medicine's humors and miasma.

    So many things that I once knew, I now know are not so. Knowing that I was mistaken then, how can I continue to say "I know" ? 

    Posted by wmr

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  6. Jason, I don't think things are quite as catastrophic as you suggest. In particular, I think the case you present *is* one of genuine knowledge. Notice that it is quite different in structure from the Gettier cases. The crucial difference is seen by considering the counterfactual: would the belief be true if it weren't for the unknown background condition?

    In the BIV case, if my vat wasn't luckily near a tree, then my belief would be false. However, in your case, even if you didn't get syphilis in the past, you certainly would have by injecting yourself with the culture! So you definitely know you have syphilis (in the hypothetical example, of course), despite being mistaken about the cause.

    One response to Gettier cases is to modify the JTB analysis to include a defeasibility clause. That is, we require that there isn't some crucial bit of background information (e.g. you're driving through fake barn country; or you're a BIV) which would cause you to retract your belief upon learning of this new info. Is this the sort of thing you meant by "contextually justified"? Because I'm not sure how appealing to context can explain why we don't know in Gettier cases - I would have thought that the man in fake barn country is still "contextually justified" in believing the barn is real? Yet he doesn't know it, so the same problem seems to apply.

    wmr - since truth is a necessary condition for knowledge, it follows that you cannot really know something false. You merely think you know it, but you're mistaken. Knowledge need not be certain (the spectre of skepticism has convinced most epistemologists to endorse fallibalism about knowledge). Some of our justified beliefs are false, others are true. We mightn't be able to tell which are which, but that doesn't matter. The true ones make up our "knowledge". We just can't be certain of which those are.

    Genius: I actually quite like the idea of saying the BIV does have knowledge - just of the 'common world' rather than the 'objective world' (see here).

    We can modify my example to escape this objection, however, by changing the belief to, e.g., "I - objectively - am located within ten (objective) metres of an (objective) tree". 

    Posted by Richard

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  7. "we require that there isn't some crucial bit of background information (e.g. you're driving through fake barn country; or you're a BIV) which would cause you to retract your belief upon learning of this new info. Is this the sort of thing you meant by "contextually justified"? Because I'm not sure how appealing to context can explain why we don't know in Gettier cases - I would have thought that the man in fake barn country is still "contextually justified" in believing the barn is real? Yet he doesn't know it, so the same problem seems to apply."

    Yes. I think that's what I meant by begging the question--We're right back at square one. I think, though, that it's not such a bad place to be. Facts don't really exist outside of their contexts, and we are looking only for a definition of knowledge, not a key to omniscience. 

    Posted by Jason Kuznicki

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  8. ---Some of our justified beliefs are false, others are true. We mightn't be able to tell which are which, but that doesn't matter. The true ones make up our "knowledge". We just can't be certain of which those are.


    Does this mean that "know" is like "grue" and "bleen"? 

    Posted by wmr

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  9. Richard,

    First, I think your lecturer was talking about Goldman's "Henry in barn-facade country," originally published as a part of the article, "Discrimination and Perceptual Knowledge."

    Second, what's the justification for the belief? Are you justified in believing there is a tree nearby b/c the tree has caused you to think there is a tree nearby? Or, are you justified in believing there is a tree nearby b/c you have reliable evidence that that thing is a tree?

    If you're a b-i-v (& you know you're a b-i-v), then you don't know that that is a tree. Hey, there's a tree nearby. So, you're not a b-i-v. I take it that this will work out to be a paradox on your account.

    Also, you might want to check out Feldman's stuff b/c these are Gettier cases that do not rest on false assumptions: I have good evidence that that's a zebra (but what I see is a horse spray-painted to look like a zebra). I can trust my evidence usually. When I have good evidence to believe that something is a P, I can infer that there is a P. So, there is a zebra on the savannah. There is a zebra on the savannah out of view, besides the horse spray-painted to look like a zebra. 

    Posted by Joe

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  10. "Know" is still meaningful as a word: It means not that we have entirely certain knowledge of something, but rather that, given absolutely all the information we have, there is no cause whatsoever for doubt of the proposition. I can live with this; by contrast, complaining that we aren't omniscient seems a rather futile way of looking at knowledge. 

    Posted by Jason Kuznicki

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  11. Yeah, what Jason said :)

    Joe, I'm inclined towards the coherence theory of justification (but not knowledge, nor truth either). We're generally justified in believing what our senses tell us, because that's what best coheres with the rest of our beliefs (even if they're all mistaken).

    But yes, I can see why some people (i.e. externalists) would deny that the BIV is justified in his beliefs. So my case wouldn't work against them. 

    Posted by Richard

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