Nathan Ballantyne

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.