Abstract

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.