Nathan Ballantyne

Two theses figure centrally in work on the epistemology of disagreement: Equal Weight (‘EW’) and Uniqueness (‘U’). According to EW, you should give precisely as much weight to the attitude of a disagreeing epistemic peer as you give to your own attitude. U has it that, for any given proposition and total body of evidence, some doxastic attitude is the one the evidence makes rational (justifies) toward that proposition. Although EW has received considerable discussion, the case for U has not been critically evaluated. Endorsing U, we argue, commits one to the highly controversial thesis that whatever fixes your rational attitudes can do so only by fixing what evidence you have. This commitment imposes a relatively demanding requirement on justified belief in U, one that we argue is not satisfied by what is currently the strongest available case for U, due to Roger White [2005]. Our challenge to U makes more trouble for its proponents than do the worries about U expressed by Gideon Rosen [2001] and Thomas Kelly [2010]. Moreover, if Kelly [2010] is correct in thinking that EW “carries with it a commitment to” U—a claim which we accept for reasons similar to Kelly’s but is beyond this paper’s scope (but see Ballantyne and Coffman [forthcoming])—then our challenge to U bears importantly on EW: to the extent that our challenge to U succeeds, EW also suffers.

Two common theses in contemporary epistemology are that ‘knowledge excludes luck’ and that knowledge depends on ‘purely epistemic’ factors. In this essay, I shall argue as follows: given some plausible assumptions, ‘anti-luck epistemology,’ which is committed to the fi rst thesis, implies the falsity of the second thesis. That is, I will argue that anti-luck epistemology leads to what has been called ‘pragmatic encroachment’ on knowledge. Anti-luck epistemologists hoping to resist encroachment must accept a controversial thesis about true belief or a dubious claim about luck and value and interests.

Two theses are central to recent work on the epistemology of disagreement: Conciliationism:?In a revealed peer disagreement over P, each thinker should give at least some weight to her peer's attitude. Uniqueness:?For any given proposition and total body of evidence, the evidence fully justifies exactly one level of confidence in the proposition. 1This paper is the product of full and equal collaboration between its authors. Does Conciliationism commit one to Uniqueness? Thomas Kelly 2010 has argued that it does. After some scene-setting (?1), in?2 we explain and criticize Kelly's argument, thereby defeating his larger argument that Conciliationism deserves no dialectical special treatment. But we argue further that Conciliationists are committed to a disjunction, one of whose disjuncts is Uniqueness, that amounts to an?extremely strong and unobvious position? (??3?4). If we are correct, theorists should not treat Conciliationism as a default position in debates about the epistemic significance of disagreement.

David Lewis and Peter van Inwagen have claimed that there are no “knockdown” arguments in philosophy. Their claim appears to be at odds with common philosophical practice: philosophers often write as though their conclusions are established or proven and that the considerations offered for these conclusions are decisive. In this paper, I examine some questions raised by Lewis’s and van Inwagen’s contention. What are knockdown arguments? Are there any in philosophy? If not, why not? These questions concern the nature of the philosophical enterprise and our answers have implications for the limits on the attitudes of informed, rational thinkers.