Main authors discussed: David Lewis and Jason Stanley

The fallibilist claims that it’s possible to know p even if your evidence for believing p does not entail p.  It seems that infallibilism entails scepticism because it seems that we don’t have infallible grounds for most of our beliefs about the external world.  Trent Dougherty and Patrick Rysiew defend fallibilism from David Lewis’ criticism and address Jason Stanley’s criticism of Rysiew’s earlier response to Lewis.

As Lewis (1996: 550) observed, overt statements of the fallibilist view seem contradictory.  Consider this concessive knowledge attribution (CKA):

(1)     I know that Harry is a zebra, but it might be that Harry is just a painted mule.

Lewis claims the second conjunct flatly denies what the first asserts.  Rysiew (2001) defended fallibilists from the charge that their view is contradictory, arguing that CKAs only seem contradictory.  In ordinary speech, he said, “It might be that ~p” pragmatically imparts that the speaker doesn’t know that p (2001: 493).

Stanley (2005) criticized Rysiew’s proposed defense because it didn’t offer any semantic account of epistemic possibility statements.  Rysiew agreed with Lewis that (1) captured the fallibilist’s view but claimed that (1) could express a truth.  The problem, according to Stanley,  was that given a standard treatment of epistemic modals Rysiew’s defense would fail.  Consider:

(EPk)     p is epistemically possible for S iff ~p isn’t obviously entailed by something S knows.

If (EPk) is correct, (1) entails:

(2)     I know that Harry is a zebra, but I do not know that Harry is not just a painted mule.

Since (2) must be false, it appears (1) must be false as well.

Dougherty and Rysiew (2009) offer a defense of fallibilism that builds on Rysiew’s (2001) earlier work and meets Stanley’s challenge to provide a semantic account of epistemic possibility statements on which (2) isn’t a consequence of (1).  Siding with Lewis against Stanley, they say that (1) does capture the fallibilist’s view.  Against Lewis, they insist that (1) can express a true proposition.  To explain how (1) could be true when it is agreed by all that (2) is false, they reject (EPk) and offer in its place this account of epistemic possibility:

(EPev)     p is epistemically possible for S iff ~p isn’t entailed by S’s evidence.

To explain why (1) seems defective, they give a pragmatic explanation.  If there are genuine reasons to doubt (i.e., reasons to doubt that do not arise simply from the recognition that there is some non-zero chance of having made a mistake), then it is acceptable to assert ‘It might be that ~p’, but inappropriate to ascribe knowledge to oneself given that there are genuine reasons to doubt.  According to Grice’s Maxim of Quality, you shouldn’t say what you believe you lack adequate evidence for.  To say that you know, you deny that you lack adequate evidence for your belief and this clashes with the claim that there are real reasons for doubt.  If, however, the reasons to doubt are simply that there is some non-zero chance of being mistaken it seems Grice’s Maxim of Relation recommends not introducing such chances into the conversation by asserting that it is epistemically possible that ~p  since these are not significant reasons for doubt (2009: 129).

Their pragmatic account may be sufficient to explain the oddity of CKAs, but note that to meet Stanley’s challenge they replaced (EPk) with (EPev).  They can’t do this without rejecting Williamson’s claim that evidence just is knowledge:

(E=K) S’s evidence consists of all and only the propositions known to S.

Their defense of fallibilism succeeds only if Williamson’s equation (E = K) is wrong.  They acknowledge this in a footnote saying, “that principle is sufficiently controversial that most would join us in assuming that the distinction between (EPk) and (EPev) is real” (2009: 127).

While (E=K) is controversial, I wish they had said more about the relation between (EPk) and (EPev) than just this.  There are two reasons that I think (E=K) needs to be revised.  According to (E = K) if you know p non-inferentially, you can then add additional propositions to your body of evidence via competent deduction.  That seems odd.  I think of inference as a way of applying old evidence to justify new beliefs and acquire new knowledge without having to acquire new evidence.  According to (E = K) if you know p and someone else fails to know p for purely Gettierish reasons, you have evidence they lack.  That seems odd, too.

If we revise (E=K) to accomodate these points, it seems we could still say that there is this connection between knowledge and evidence:

(IKSE)     If S knows p non-inferentially, p is part of S’s evidence.

If (IKSE) is true, immediate knowledge of p’s truth suffices for p’s inclusion in your evidence. While (E = K) might be controversial, (IKSE) seems far less controversial.  To deny it, you have to say that more is needed to get p into your evidence than just non-inferential knowledge.  (Remember that we want a non-sceptical view.  If we want a non-sceptical view, should we really insist that we need more than knowledge to get something into our evidence?  What would that be, superknowledge?)  If (IKSE) is true, a CKA of the form ‘I know p, but it might be that ~p’ would express a false proposition on Dougherty and Rysiew’s view if the speaker knew non-inferentially that p.

Let ‘p’ be the proposition that S has hands.  If S could assert truthfully that it is possible that she does not have hands (or that she’s a handless BIV), according to (EPev) S’s evidence does not include the proposition that she has hands.  (The only way that they could deny that S could assert this truthfully is if they say that whenever S knows she has hands she has evidence that entails that she has hands.)  It follows from the fact that her evidence does not include the proposition that she has hands and (IKSE) that she does not know that she has hands.  Perhaps they will just deny (IKSE), but (IKSE) is a consequence of:

(IJBSE)     If S is non-inferentially justified in believing p, p is part of S’s evidence.

If they deny (IKSE) they also have to deny that S can be non-inferentially justified in the belief that she has hands.  As a fallibilist, I’d prefer to retain (IJBSE) and (IKSE) if possible.

Reviewed by Clayton Littlejohn
Southern Methodist University

7 Comments

• By Trent Dougherty, April 3, 2009 @ 10:12 am

  Have a new baby in the house, so can only leave brief remark.

  Can’t speak for Patrick of course, but my own view is that the relationship between knowledge and evidence is essentially just as Richard Jeffery has it in his probability kinematics.

  This is mentioned in a forthcoming follow up by Patrick and me.
• By Clayton Littlejohn, April 3, 2009 @ 11:37 am

  Hey Trent,

  I’m glad you came by to comment and I’d be interested to see what’s in the follow up piece. I don’t know what Jeffrey’s views are on the relationship between knowledge and evidence, but I take it that your view faces (at least) two significant challenges. The first is that by asserting (EPev) and denying (EPk), you have to give up the idea that immediate knowledge of p’s truth (e.g., observation that p is true) is sufficient for getting p into your evidence or you have to deny that we can have immediate knowledge of the external world. The second is that by denying (EPk), you throw away the thing that gives us the obvious explanation as to why ‘must’ is factive. I think Hawthorne thinks there is some linguistic evidence that suggests that ‘must’ is factive and I don’t see given what I think you’d assume about evidence my epistemic necessities are, inter alia, truths.
• By Trent Dougherty, April 4, 2009 @ 1:22 pm

  Also just noticed one other thing. You only give the entailment reading of EPev. I personally prefer the probabilistic reading we gave, that EPoss(P) for S iff P has non-zero probability on S’s total evidence.

  This way, given Jeffrey’s probability kinematics we can accept E = K and still maintain the distinction between our view and the received view.
• By Clayton Littlejohn, April 5, 2009 @ 10:40 pm

  Trent,

  I think that’s an interesting point, but I’m still not sure if it takes care of the worry.

  Suppose S knows (non-inferentially) that she has hands. Given (E=K), the proposition that she has hands is part of S’s evidence. The probability that there is at least one hand on S’s total evidence should be 1.

  However, suppose we ask S to consider some sceptical scenarios and she says ‘It might be that there are no hands, just hand appearances.’ Intuitively, she speaks properly. The probability that there is at least one hand on S’s total evidence is less than 1. So, she doesn’t have the proposition that she has hands as part of her evidence. So, she doesn’t know she has hands.

  Should we say that she doesn’t know she has hands just because she can properly say that it might be that there are no hands having thought about some sceptical scenarios? I think not. But, then I’d have to say that the proposition that she has hands is part of her evidence, the probability that there is a hand on her evidence should still be 1, and so I can’t see how it shouldn’t be epistemically necessary for her.

  It seems rejecting (E=K) would be the natural way to go for you if you accept (EPev) in either of its guises. Rejecting (E=K) only gets you part of the way. It seems you’ll need to reject (IKSE) and (IJSE), too.
• By Clayton Littlejohn, April 5, 2009 @ 10:41 pm

  Oops, I should have said:

  “However, suppose we ask S to consider some sceptical scenarios and she says ‘It might be that there are no hands, just hand appearances.’ Intuitively, she speaks properly. Given (EPev), the probability that there is at least one hand on S’s total evidence is less than 1. So, she doesn’t have the proposition that she has hands as part of her evidence. So, she doesn’t know she has hands.”
• By Trent Dougherty, April 6, 2009 @ 9:46 am

  The mistaken premise above is “The probability that there is at least one hand on S’s total evidence should be 1″ This isn’t true even given E = K because the Pr(X/X) which is admittedly one is weighted by Pr(X) which is less than 1. In probability kinematics the key idea is this “weighting” of each conditional probability by the unconditional probability. Our base-line observational data is sub-certain (as is intuition, memory, and even introspection), and so nothing ever comes out certain (on the view I accept).
• By Clayton Littlejohn, April 6, 2009 @ 9:31 pm

  Trent,

  I don’t see that there’s a mistake in the premise. It seems that you’re just agreeing with my point that you can’t say that you can’t say both:
  (i) If S knows p non-inferentially, p gets into S’s evidence;
  (ii) S can know non-inferentially propositions about the external world.

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