Kalhat has forcefully criticised Wittgenstein's linguistic or conventionalist account of logical necessity, drawing partly on Waismann and Quine. I defend conventionalism against the charge that it cannot do justice to the truth of necessary propositions, renders them unacceptably arbitrary or reduces them to metalingustic statements. At the same time, I try to reconcile Wittgenstein's claim that necessary propositions are constitutive of meaning with the logical positivists' claim that they are true by virtue of meaning. Explaining necessary propositions by reference to (...) linguistic conventions does not reduce modal to non-modal notions, but it avoids metaphysical accounts, which are incapable of explaining how we can have a priori knowledge of necessity. (shrink)