Reply: It is true that on any precisification there will be no principled reason why this fusion of rocks is a mountain, and another is not. And it is true that there should be such a principled reason; mountainhood facts are not basic. But that problem can be avoided by the theory that denies that “the supervaluationist rule [applies] to any statement whatever, never mind that the statement makes no sense that way” (Lewis 1993, 173). Lewis's idea, or at least the application of Lewis's idea to this puzzle, is that we know how to understand the idea that mountainhood facts are non-arbitrary: we understand it as a claim that there is some non-arbitrary explanation of which precisifications of ‘mountain’ are and are not admissible. If we must apply the supervaluational rule to every statement, including the statement that it is not arbitrary which things are mountains, this understanding is ruled out. Lewis's response is to deny that the rule must always be applied. As long as there is some sensible way to understand the claim, we don't have to insist on applying the supervaluationist machinery to it. 