 Peter van Inwagen (1983: 202–04) argues that the PSR must be rejected. If the PSR is true, every contingent proposition has an explanation. Suppose P is the conjunction of all contingent true propositions. Suppose also that there is a state of affairs S that provides a sufficient reason for P. S cannot itself be contingent, for then it would be a conjunct of P and entailed by P, and as both entailing and entailed by P would be P, so that it would be its own sufficient reason. However, no contingent proposition can explain itself. Neither can S be necessary, for from necessary propositions only necessary propositions follow. Necessary propositions cannot explain contingent propositions, for if x sufficiently explains y, then x entails y, and if x is necessary so is y. S cannot be either contingent or necessary, and hence the PSR is false. Thus, if the cosmological argument appeals to the PSR to establish the existence of a necessary being whose existence is expressed by a necessary proposition as an explanation for contingent beings, it fails in that it cannot account for the contingent beings it purportedly explains. 