This essay examines how, in the early twentieth century, ontological arguments were employed in the defense of metaphysical idealism. The idealists of the period tended to grant that ontological arguments defy our usual expectations in logic, and so they were less concerned with the formal properties of Anselmian arguments. They insisted, however, that ontological arguments are indispensable, and they argued that we can trust argumentation as such only if we presume that there is a valid ontological argument. In the first (...) section I outline the history of this metalogical interpretation of the ontological argument. In the subsequent sections I explain how Royce and Collingwood each developed the argument, and how this impacted their respective conceptions of both logic and metaphysics. (shrink)

Chalmers has argued that Bayesianism supports the existence of a priori truths, since it entails that scrutability conditionals are not rationally revisable. However, as we argue, Chalmers's arguments leave open that every proposition is rationally deniable, which would be devastating for large parts of his philosophical program. We suggest that Chalmers should appeal to well-known convergence theorems to argue that ideally rational subjects converge on the truth of scrutability conditionals. However, our discussion reveals that showing that these theorems apply in (...) effect requires assuming scrutability. Consequently, Bayesianism doesn't conflict with Chalmers's scrutability framework, but it doesn't support it, either. (shrink)