The Probability of the Possible

In “Why is There Anything at All?” Peter van Inwagen argues that even though it was never necessary that concrete beings existed, it was always maximally probable – just short of necessity – that they did . I argue that van Inwagen’s argument fails, albeit for an interesting reason which has remained so far unnoticed in the literature: there is a critical ten- sion between two of its premises, both essential to its soundness, concerning the nature of comprehensively specified possible worlds. I summarize van Inwagen’s argument, develop this objection, and then describe more problems which invariably accrue when we try to ascribe probability values to possible worlds