Evaluating the Theistic Implications of the Kantian Moral Argument that Postulating God is Essential to Moral Rationality

Abstract

I contend that Kant’s moral argument that postulates God and an afterlife in order to justify moral rationality counts strongly in favor of theistic ethics even though it cannot on its own justify that God exists. In moving toward this conclusion, I assess Kant’s moral argument and note how both Kant and the utilitarian Henry Sidgwick, in their own ways, recognize that morality cannot reasonably be seen as completely overriding if God and an afterlife are rejected. I then critique a theistic moral rationality argument offered by C. Stephen Layman, as a flaw in this argument helps to reveal why arguments centering upon moral rationality likely cannot reach an ontological conclusion concerning theism; nevertheless, I contend that moral rationality arguments like Kant’s have apologetic significance for theism. They reveal a dilemma for secular ethics: either appeal to the possibility of theism in order to justify moral rationality or else accept that morality is not fully rational.