True Believers

I was looking around for stuff by other heretics in the knowledge debate so I googled Crispin Sartwell and found his webpage. Despite not containing much epistemology, it is a lot of fun. I rather liked (despite not at all agreeing with) his ranking of major philosophers on a 1-10 scale. On that note, yet another argument that knowledge is justified true belief is below the fold. (Exercise for the readers – find where if anywhere I’ve appealed to justification in this argument.)

This one isn’t entirely original – it’s just a variation of an argument John Hawthorne has discussed on various occasions.

1. S is a speaker and H a hearer such that

  • S JTBs p and S doesnt know that p
  • S and H know each other to be generally reliable informants
  • S tells H that p, although S is uncertain whether H already knows that p
  • On this basis H comes to believe that p
  • Then H tells S that p
  • S comes to regard Hs testimony as her primary reason for believing that p

2. H knows that p, since belief based on true testimony from a known to be reliable source constitutes knowledge.

3. After receiving Hs testimony, S knows that p, since belief based on true testimony from a known to be reliable source constitutes knowledge.

4. Before receiving Hs testimony, S knows that p, since Hs testimony doesnt improve Ss epistemic position, and she knows that p after receiving Hs testimony.

5. Since the existence of H satisfying the conditions in 1 is irrelevant to whether S knows that p, all Ss such that they JTB that p know that p.

Premise 1 is just a setup, the work is done in 2, 3, 4 and 5. Someone who doesn’t believe the JTB thesis has to deny one of these inferences. I think each of them is individually plausible, though obviously that doesn’t imply very much about the plausibility of their conjunction.

5 Replies to “True Believers”

  1. Perhaps I’m just dense, but ‘S JTBs p and S doesnt know that p’ doesn’t seem to work with 4. I guess I don’t see the implicit argument for ‘Hs testimony doesnt improve Ss epistemic position’.

  2. How interesting — I’m inclined to reject every single step in your argument! In my opinion:

    2 is false because it is not enough for the source to be “generally reliable”; the source must be reliable about the very proposition in question. 3 is false for the same reason.

    4 is false because H’s testimony does improve S’s epistemic with respect to p — H might have had defeating evidence against p, and S learns (in effect) that H doesn’t. The same point shows that 5 is false: H’s intervention is not “irrelevant” at all.

    So, in my opinion, your argument is really quite impressively unsound!

  3. Putting my caring-about-knowledge hat on, I’m certainly inclined to deny 2. There are cases in which testimony can generate knowledge, but this doesn’t look like one of these cases; if S is Gettiered so is H. (Though I am somewhat impressed by your long-chain-of-testimony cases.)

    Ralph, I’m not sure what it is for S to be reliable on a single proposition. Are you adverting to modal stability?

  4. I suppose people might kick up a fuss about S violating the norm of assertion; and perhaps one may want to make some heavy weather about the reliability of testimony when the norm of assertion is broken. For my part, being a knowledge-as-true-belief kinda guy, I would like the argument but premise 1 strikes me as (obviously) fishy.

  5. Matt, yes, absolutely, I mean modal stability. Roughly, a method is “reliably error-avoiding” about a proposition p in circumstances C just in case in none of the “nearby” possible worlds in which the believer uses that method in circumstances C does the method yield a false belief (either in p or in any other closely related proposition). For knowledge, the method must also be “rational” and “reliably belief-yielding” as well (roughly, it must not be the case in any nearby possible world that the believer uses the method but encounters defeating evidence and so does not form the belief in question).

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