The Epistemology of Disagreement: Puzzles, Solutions, and Applications

This is a dissertation about the epistemology of disagreement. The main questions addressed here are, Can one rationally retain a belief in the face of disagreement with one's acknowledged epistemic peer? And if so, how? I argue that such questions are best addressed when transformed into puzzles (clusters of individually plausible, but jointly inconsistent claims). In chapter 1, I provide important background relevant to the setup of epistemological puzzles about peer disagreement. I begin by canvassing extant notions of disagreement, epistemic peers, and positive epistemic status. I then identify the main ingredients for an epistemological puzzle about disagreement. One recipe for such puzzles minimally includes: • A claim describing the epistemic situations of the relevant subjects vis-à-vis the target proposition (e.g., that the subjects are epistemic peers with respect to this proposition). • An epistemic principle stating that if the relevant subjects' epistemic situations are as described in the first claim, then their attitudes toward the target proposition do not have such-and-such an epistemic status (e.g., these attitudes are not rational, or do not amount to knowledge). • A claim to the effect that the relevant subjects' attitudes do have such-and-such an epistemic status. A central puzzle addressed here employs an epistemic principle claiming that in all cases of acknowledged peer disagreement, disputing parties are rationally required to move from belief (disbelief) to withholding. Coupled with the claim that peer disagreement is common, this principle appears to lead to a variety of skepticism that threatens many of our most cherished beliefs. Any complete defense of these beliefs, then, must face the problem of peer disagreement. In chapter 2, I argue that acknowledged peer disagreement is rare, at least in cases of more than modest complexity. The conditions for acknowledged peerhood - (a) sameness of evidence, (b) equal reliability, and (c) good reason to think (a) and (b) obtain - are not easily met. When one of these conditions fails to obtain, acknowledged peerhood fails to obtain. Inasmuch as acknowledged peer disagreement is rare, any case for wide-ranging, peer-disagreement-based skepticism fails. But suppose that acknowledged peer disagreement were common. Would we then be faced with widespread skepticism about all our disputed, but cherished beliefs? In chapters 3 and 4, I argue that we would not. In chapter 3 I consider the prospects for defeating skepticism by appealing to factors (e.g., background beliefs and 'private' evidence) that may make it rational for both parties to a dispute to retain belief in the face of peer disagreement. I argue that such appeals have limited application, but are not wholly without merit. In chapter 4 I consider an anti-skeptical strategy according to which one (but not both) parties to a peer disagreement may rationally retain belief. This strategy appeals to the character of the first-order evidence that is shared in cases of peer disagreement. I argue that if this evidence strongly supports the attitude of one peer over that of the other, then the former peer may be rational in retaining her belief (albeit with reduced confidence) in the face of peer disagreement. In arguing for this claim, I utilize insights from extant theories of epistemic defeat. In chapter 5, the discussion turns from the topic of rational belief to the topic of disagreement and knowledge - in particular, moral knowledge. There I consider four disagreement-based arguments for skepticism about moral knowledge. Applying insights gleaned from previous chapters, I conclude that three of these arguments fail. I close the chapter, and the dissertation, by offering what I regard as a more promising - though not decisive - skeptical argument.