Jack has been posting on epistemic closure principles. I know that I have hands. I also know that, if I have hands, then I'm not a (handless) brain in a vat (BIV). But, it's generally supposed, I can't know that I'm not a BIV.
Something weird's going on here. For an intuitive complaint, look at the abominable conjunctions:
# I know that I have hands, but I don't know that I'm not a handless BIV.
# (Expressed in assertion:) "I have hands, but I can't say whether I'm a handless BIV."
For a principled complaint, it makes no sense to think that I could have less epistemic warrant or evidence for the logically weaker claim. The other entails it. The worlds where I have hands are a proper subset of the worlds where I'm not a handless BIV. It's as silly as thinking that Linda is more likely to be a feminist bank teller than a bank teller.
My favoured solution is due to Keith DeRose. S's belief that P is epistemically safe precisely to the extent that certain possible worlds -- namely, those where S believes P falsely -- are distant. Degree of safety is the fundamental epistemic property, and it satisfies closure principles perfectly, as we should expect. I think I have hands, and I think I'm not a BIV, and the latter belief is at least as safe as the former. (You'd have to go out to at least as distant a possible world in order to find one where I hold the belief falsely.)
Why do closure principles seem to fail for knowledge, then? Simply because the standards for knowledge vary. Knowledge is belief that is sufficiently safe for our purposes. Whether a belief that's safe to degree N so qualifies is an open question, and one that will receive different answers in different contexts. Raising certain possibilities to salience will tend to raise the bar, requiring that the safety level of the belief extend to the possible worlds under consideration. Once the bar is raised so high, even our ordinarily safe beliefs will not qualify as "knowledge". Abominable conjunctions are thus avoided.
So we find that the apparent failure of closure is an artifact of our shifting standards. At the fundamental level, epistemic qualification (i.e., safety) transmits across entailments just fine.
Saturday, March 22, 2008
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Personally, I'm with Moore on this one. I know I'm not a brain in a vat, and the contrary being generally supposed is no proof of the contrary.
ReplyDeleteYeah, I'm sympathetic to that -- certainly by everyday standards of safety we know it, and I see little reason to raise the bar excessively, even in the seminar room. But it should be uncontroversial that the standards for knowledge can vary to some degree. So that will lead to (less radical) closure violations all the same.
ReplyDeleteMundane example: I know the bank closes at 5pm. But now suppose it's mid-afternoon, and I desperately need to complete a transaction today (or I'll lose my house or something). I wonder whether I can safely wait till after 4pm, and I realize: I don't know that the bank doesn't close as early as 4pm. Not when the stakes are this high.
Sensible explanation: my belief is no less 'safe' or epistemically qualified than before; but raising the stakes changes what counts as sufficiently safe for my purposes.
For a principled complaint, it makes no sense to think that I could have less epistemic warrant or evidence for the logically weaker claim. The other entails it. The worlds where I have hands are a proper subset of the worlds where I'm not a handless BIV.
ReplyDeleteThis assumes that there is no equivocation, and I'm not sure that this can be assumed. Consider:
"I am a handless BIV. But obviously I do have hands, in a different and even primary sense: namely, I have these things, which are waving at you, picking up this book, and beginning to throw it at your head."
On such a view we get the opposite of your suggestion: The possible worlds should be viewed in light of what I know in each, and the possible worlds in which I know that I have these, which we call hands, and am yet a brain in a vat, is a proper subset of the worlds in which I have these, which we call hands.
The real problem here, I think, was noted by Berkeley: these skeptical scenarios about the general veridicality of sense perception really do nothing more than split the external world into two different, arbitrarily regimented external worlds: one the world I sense, the world of the phenomena, to which I normally refer, and the other a world I (apparently) have no direct access to, which is (again arbitrarily) supposed to be the real world.
Brandon - true! One of my very first blog posts expounded just that view. But it won't generalize to more mundane cases, e.g. my bank example above, or Dretske's zebra / "cleverly disguised mule" that Jack discusses.
ReplyDeleteSo really that was just a poor choice of initial example on my part. (I have an impractical fondness for BIVs.)
On your bank example, I think we have to be wary of possible contamination from other intuitions. For instance, one could argue that you know that the bank closes at 5 pm as a general rule, based on the fact that it always does; but you don't know that it does so today (because some banks sometimes do close early).
ReplyDeleteWhat I take it that you and DeRose are proposing is an epistemological version of casuistry (in the old, non-derogatory sense, as in disputes between probabilists, probabiliorists, and rigorists). Different contexts lead to accepting different beliefs as sufficiently safe. One difficulty with this view, if the analogy is at least roughly right, is that matters vary not only according to beliefs but also according to reflex principles -- i.e., to the principles governing your assessment of whether those false-belief possible worlds are distant enough.
Richard,
ReplyDeleteI should probably look this up myself, but what does DeRose say about dreaming (hallucination, etc..) skepticism? As much as I understand the notion of a distant possible world (and I confess that that's not lots), worlds in which I'm dreaming aren't especially far from worlds in which I'm not. But, dreaming skepticism is sufficient to put most of our common sense knowledge into doubt.
Jack - I don't know about DeRose, but my response to dream skepticism is here.
ReplyDeleteRichard,
ReplyDeleteInteresting post. And thanks for the comments.
One strange thing about your view is that it predicts that there are some conversational contexts in which someone does not know that they have hands but does know that they are not a handless brain in a vat. That seems weird, backwards even.
"For a principled complaint, it makes no sense to think that I could have less epistemic warrant or evidence for the logically weaker claim."
Sure it does. Consider the mathematical cases, or the metaphysical cases, or the a priori truth cases.
Hi Jack,
ReplyDeleteAren't those cases you mention merely a matter of not fully understanding what's being claimed? I have trouble imagining a case where I knew that one claim was logically weaker than (i.e. entailed by) another, and yet still thought I had better epistemic support for the truth of the latter!?
"One strange thing about your view is that it predicts that there are some conversational contexts in which someone does not know that they have hands but does know that they are not a handless brain in a vat. That seems weird, backwards even."
Really? That doesn't seem weird to me. Suppose I remind you of the psychological experiments wherein subjects see the experimenter's hands move and mistakenly believe that the hands are their own. I might cleverly raise to salience some local-skeptical possibility that you don't really have hands at all. (I'm not clever enough to do this convincingly here, alas.) If you can't rule out this alternative possibility which I've raised to salience, you won't qualify as knowing that you have hands. But your ordinary knowledge that you have a body (i.e. that you are not a BIV) remains unthreatened.
(Don't let your intuitions here be fooled by the fact that mentioning the BIV belief might raise the contextual standards to a higher level so that it no longer counts as sufficiently safe to qualify as knowledge.)
"I have trouble imagining a case where I *knew* that one claim was logically weaker than (i.e. entailed by) another, and yet still thought I had better epistemic support for the truth of the latter!?"
ReplyDeleteLooks who's raising the epistemic standards!
"Aren't those cases you mention merely a matter of not fully understanding what's being claimed?"
No. I understand what's being claimed in the Goldbach Conjecture, and what's being claimed by "that there are concrete possible worlds" or "that the morally better action of A and B is the one with the better expected consequences" at least as well as I understand what's being claimed in "that I have hands." Indeed, hands have turned out to be strange things, mostly hollow, wave-like...
"Really? That doesn't seem weird to me."
Come on. Maybe I wasn't as precise as I should have been. It's easy to come up with a situation in which a person knows that they are not a handless brain in a vat but does not know that they have hands. Take someone who believes that they are not a handless brain in a cat but does not believe that they have hands. (Your situation sounds like one in which you could get a person to temporarily not believe that he has hands). What is strange is to have someone who believes both that he has hands and that he is not a BIV, and yet because of the epistemic context, not know that he has hand but know that he is not a BIV. I think that is really strange.
No, that's precisely the sort of situation I meant to describe. You still believe you have hands, just as you always believe you're no BIV. It's just that I've raised to salience an alternative possibility to the former (only) that you can't rule out. There's nothing at all odd about this. It's a straightforward implication of the fact that it's (metaphysically) easier for us to be wrong about having hands than about not being BIVs. There are moderately distant possible worlds where our hand-belief is in error and yet our non-BIV belief remains true and safe as ever. Raise this world to salience and you immediately cast doubt on the former belief but not the latter. It's not odd; it's entirely to be expected.
ReplyDelete(Note that you have to raise the standards to extend to very distant worlds, by contrast, before our non-BIV belief could go wrong. It's really very rare to be in a context in which our non-BIV belief fails to qualify as knowledge. But again, this may not seem intuitive for the reason noted in my previous comment.)
"Looks who's raising the epistemic standards!"
Funny. But you know I was just being sloppy earlier; the closure principles we're interested in are typically understood as 'closure under known entailment'. (I agree that lacking epistemic support for a secretly logically weaker claim is not so mysterious. But that's besides the point.)
Here's one thing I couldn't wrap my head around in my Contexualism course at NIU.
ReplyDeleteHow can we say "You'd have to go out to at least as distant a possible world in order to find one where I hold the belief falsely?"
How do we know that a world where you hold a false belief is a far away one?
I think I get this:
S's belief that P is epistemically safe precisely to the extent that certain possible worlds -- namely, those where S believes P falsely -- are distant.
But, how are we supposed to know which worlds are close and which are far - especially when knowledge is precisely what we're questioning?
Is there something really obvious I am missing in discussions like these?
Mathew - see my post 'Know Show', which clarifies the dialectic here, explaining why it's legitimate for anti-skeptics to assume that the beliefs in question are true (at least for the sake of this argument).
ReplyDeleteOr do you mean to suggest that there's something especially dubious about those modal assumptions? I'm not sure why that would be. How 'distant' another world is simply depends on how different it is from our world. Supposing that I really am an unproblematically embodied human with hands, etc., things would have to be drastically different in order for me to be a BIV. That's why (I suppose that) the BIV world is distant.
(But again, if you're puzzled by why I'm allowed here to suppose that I have hands at all, follow the above link.)