When peers disagree : an essay in the epistemology of peer disagreement

Thesis (Ph. D.)--University of Rochester. Dept. of Philosophy, 2010.My aim in this dissertation is to contribute to the existing literature on the epistemology of peer disagreement. Toward that end, I do the following. In Chapter 1, I consider and reject a number of proposed characterizations of the concept of disagreement. I then present and defend the following analysis: For any two individuals S1 and S2, any proposition p, and any time t, S1 and S2 disagree over p at t if and only if S1 and S2 take different doxastic attitudes toward p at t. In Chapter 2, I analyze the concept of epistemic peers in part by appealing to the notion of epistemic credentials. I then note the various epistemic credentials relevant to determining epistemic peers (allowing that there may be more): justification peers, truth peers, knowledge peers, responsible inquiry peers, and information peers. I then argue (contrary to the dominant stream in the literature) that the epistemology of peer disagreement literature is best served by invoking the epistemic credential found in the concept of truth peers: For any two individuals S1 and S2, any time t, and any proposition p, S1 and S2 are truth peers at t about p if and only if S1 and S2 are equally fit at t for attaining a true belief about p. I then argue that, from among the popular competitors found in the current literature, it alone is the epistemic credential relevant to epistemic peers sufficient to raise, in a particularly compelling way, the interesting epistemological question about justification found in the literature. In Chapter 3, I do two things. First, I present and clarify one particular position advanced in the current epistemology of peer disagreement literature, namely, The Equal Weight View (EWV): For any persons S1 and S2, any proposition p and any time t, if S1 and S2 are in a peer encounter over p at t, then the opinions of S1 and S2 about p at t are worth the same evidentially. Second, I defend EWV from an objection based on The Uniqueness Thesis. I argue that EWV is not committed to (any version of) The Uniqueness Thesis, and that (some version or other of) The Uniqueness Thesis may be plausible anyway. In Chapter 4, I do two things. First, I defend EWV from the objection that it swamps the original evidence in cases of peer encounter. I argue that EWV has no such implication and even if it did, that would not be a bad result. It just seems plausible that, in standard cases of peer encounter (i.e., in cases where it is not self-defeating or defeated by other peer or superior testimony), peer testimony swamps the original evidence and is epistemically decisive (i.e., it effectively decides the justification facts). Second, I defend EWV from the charge that it has theoretical similarities with an implausible view about how to handle (rationally) intrapersonal conflict. I argue that EWV has no such similarities (because it is not a thesis about rational belief), but even if it did, that would not be bad since merely sharing some theoretical similarities with an implausible view is not by itself objectionable. In Chapter 5, I defend EWV from the charge that it licenses objectionable forms of bootstrapping. Once again, I argue that EWV has no such implications. Moreover, taking the view that peer testimony is epistemically decisive in (standard) cases of peer encounter doesn’t commit one to objectionable bootstrapping. Whatever bootstrapping it does allow is not, upon reflection, objectionable. In Chapter 6, I do two things. I defend EWV from the charge that it makes implausible distinctions between kinds of evidence. I argue that EWV all by itself makes no evidential distinctions of any kind. Once again, though, there’s no problem with thinking that peer testimonial evidence should be distinguished from other non-psychological/non-doxastic evidence (in this respect, at least): peer testimonial evidence is epistemically potent enough to swamp, and to be epistemically decisive over, any body of non-psychological/non-doxastic evidence. I show how peer testimonial evidence is sufficient to defeat (non-psychological/non-doxastic) bodies of evidence that seem especially defeat-resistant: recognized mathematical proofs and clear, vivid perceptual experiences. Second, I defend EWV from the objection that it makes it implausibly difficult to demote an individual from epistemic peer to inferior simply on the basis of (perhaps repeated) disagreements. In response to this objection, I argue that EWV all by itself doesn’t have that implication since by itself it has no implications regarding justification. Moreover, as with the other objections, the implication wouldn’t be bad anyway. I argue that it is implausible to think that one could be demoted from peer to inferior simply on the basis of subsequent disagreements. Finally, in Chapter 7, I do two things. First, I defend EWV from the charge that it is rationally self-undermining. I argue that EWV is not rationally self-undermining since by itself it makes no claims about what it is rational to believe. It can’t rationally undermine itself without prescribing what to believe. I do grant, however, that taking peer testimony to be epistemically decisive in (standard) cases of peer encounter is potentially rationally self-undermining because (given the current epistemological context) it is actually rationally self-undermining. However, I argue, this is no reason to think that that view is false. I argue (through considering several examples) that having the property being rationally self-undermining is not sufficient for having the property being false. Second, I defend EWV from the objection that it badly mishandles several cases in the literature, namely, Careful Checking and Extreme Mental Math. I do this in a roundabout way. I take the claim that peer testimony is epistemically decisive in cases of peer encounter. I then consider two different cases in the literature: Elementary Math and Perception. I argue that these cases are no trouble for the view that peer testimony is epistemically decisive in cases of peer encounter, and that considering these cases brings out some helpful points that can then be brought to bear on Careful Checking and Extreme Mental Math. Specifically, I argue that Careful Checking and Extreme Mental Math are perfectly compatible with the claim that peer testimony is epistemically decisive in cases of peer encounter. Put differently: that claim offers readings of Careful Checking and Extreme Mental Math that seem especially plausible to me. And, of course, those readings are perfectly compatible with EWV. Consequently, I argue, these cases provide no good objection to EWV. Indeed, none of the nine objections I consider in this dissertation provide good reason to reject either EWV or the principle that peer testimony is epistemically decisive in (standard) cases of peer encounter. Both remain unscathed. Consequently, when peers disagree, the truth seems to be this: (1) peer opinions are worth the same evidentially (i.e., EWV is true), and (2) peer testimony is epistemically decisive unless that testimony is self-defeating or defeated by other peer (or superior) testimony