My writings also build on existentialism. But there's a pragmatic, postmodern, aesthetic argument that follows from this contention that worldviews are fundamentally nonrational and incommensurable. You find this argument in The Life of Pi: if naturalism and monotheism have irreconcilable presuppositions, and one worldview is better for your health, shouldn't you make the existential choice to prefer that worldview? There's a meta leap of faith as we survey the possible worldviews or grand stories we can tell ourselves. Which worldview makes for the best story?