In this paper I critically examine Brian Leftow's attempt to construct a theistic semantics for counterpossibles, one that can be used to make sense of the fact that propositions, which exist necessarily, nevertheless depend on God as their cause. I argue that the impressive theoretical framework erected by Leftow cannot guarantee an asymmetrical dependence of propositions on God, and ultimately leads to a semantic collapse in which every counterpossible comes out false. I end by defending an alternative account of God and propositions – what I call ‘theistic existentialism’. It is shown how this account underwrites a semantics for counterpossibles that conveniently avoids the problems attending Leftow's theory.