Sunday, May 25, 2008

Is Knowledge (Ever) Indefeasible?

My old thread on the surprise examination paradox has seen an interesting revival of discussion. Along the way, Pablo claims:
If someone knows that Q, that person cannot be thrown into a state of epistemic confusion regarding Q.

I doubt this. It seems that in many cases knowledge can be undercut when we acquire further (perhaps misleading) beliefs. I may see (and hence know) that the widgets are red, until I form the defeating belief that they are irradiated by red light. Similarly, if an apparently infallible source ('God') tells me that I can't know that Q, his assertion may be self-fulfilling, by raising doubts and plunging me into a state of epistemic confusion and uncertainty that is incompatible with full-blown knowledge.

On the other hand, the unrestricted claim that epistemic doubts are self-fulfilling leads to contradiction when combined with other plausible assumptions (introspection and closure under known entailment). Perhaps the two most promising options are then:

(1) Allow only justified doubts to act as defeaters; or
(2) Restrict the claim, so that only undoubted doubts are automatic defeaters. If you come to believe that your doubts [about your belief that p] are unjustified, then those doubts no longer undercut the justification for your belief. (The defeater is itself defeated.)

Remaining questions: Which of these options is right? If (1), will that make some knowledge indefeasible after all? Or is the doubt and confusion raised by God's testimony justified, so that it may defeat your knowledge in any case?


  1. Seems like the old debate about whether one could know without knowing one knows.

  2. If you always know that you know then it's impossible to be thrown into confusion about what you know. If, on the other hand, you know but you don't necessarily know that you know it is very easy to be thrown into confusion.

  3. I thought that might be what you had in mind. I'm not sure it's true, though.

    (i) Suppose that, despite initially knowing that p (Kp), I may be thrown into confusion and thus have my knowledge undermined. Why couldn't this happen on two levels at once? Initially: Kp and KKp. Then I'm thrown into confusion, and subsequently both pieces of knowledge are (simultaneously) undermined. Why is this not possible?

    (ii) Suppose option #1 from my post is true, i.e. only justified doubts act as defeaters. Suppose I have a non-gettiered, justified true belief that p. I thus know that p. But then I start to have (unreasonable) doubts. For no good reason, I come to think that my above belief, though I retain it, isn't really justified. By #1, these doubts cannot defeat the actual justification my belief has, so it remains (undefeated) knowledge. But I don't believe it's knowledge, so a fortiori I cannot know that it's knowledge.

    So, I think the present issue is independent of the KK issue, in both directions.

  4. Yeah. You're right. I was definitely being brain dead in that comment.

  5. I think you may have been getting at something, though, which is the idea that whether one is susceptible to being thrown into epistemic confusion may depend upon the strength and robustness of their prior knowledge. (I take this to be related to your suggestion, because it's easy to confuse "knowing that you know that p" with the first-order trait of knowing, with near-certainty, that p.)

    Near-certain knowledge is very difficult to undermine. For example, if an apparently infallible source told me that I can't know that 2+2=4, that probably wouldn't throw me into epistemic confusion. Instead, I would simply come to think that the person I'm talking to isn't so infallible after all!

  6. Yeah, that's actually the line of thought I was thinking of simply because of the trump debate I was part of. But clearly that's wrong due to the possibility of weak knowledge.

  7. Richard, are you prepared to deny that someone could indefeasibly know that not every statement is both true and false?

  8. Pablo -- I'm not sure. It may be (as suggested in my earlier comment) that some (very rare) instances of knowledge are so certain and unshakeable that they can't be undermined by any means whatsoever. I don't think it's entirely clear, though.

    Suppose a reliable source tells you they've slipped you an irrationality pill. This pill makes obvious logical falsehoods seem to the patient like obvious logical truths. One who takes such a pill is absolutely incapable, by any means of introspection or attempted reasoning, to discern these obvious mistakes. Further suppose everyone around you starts insisting that you've taken such a pill and are simply irrational; they insist that you are wrong to believe that p [where p = "not every statement is both true and false", or whatever else you like], that really it is an obvious logical falsehood, and it only seems to you like an obvious logical truth because you've taken an irrationality pill and are now totally incapable of assessing such things. Might this be enough to throw you into a state of confusion, even for the most obvious proposition p?


Visitors: check my comments policy first.
Non-Blogger users: If the comment form isn't working for you, email me your comment and I can post it on your behalf. (If your comment is too long, first try breaking it into two parts.)