Richard Gale and Alexander Pruss (1999) advanced a modal version of the cosmological argument. They reject the strong version of the PSR, according to which “for every proposition \(p\), if \(p\) is true, then there is a proposition, \(q\), that explains \(p\)”. In its place they favor using a weak version of the PSR—it is possible that for every true proposition, there is a proposition, \(q\), that explains \(p\)—that they believe is less question-begging and more initially acceptable to critics. They phrase the argument in terms of contingent and necessary propositions. A contingent proposit...