Attainability and Kant’s Moral Argument

Abstract Kant claims that we must Believe (or have faith, Glaube ) in the attainability of our ultimate moral end – the Highest Good – and that God exists. According to a strand of orthodoxy, this claim rests on a rational principle, called Attainability: one can rationally will an end only if one thinks that it is attainable. However, this orthodox view faces four prominent objections concerning (1) acting as if, (2) the modal content of Beliefs, (3) approximation, and (4) withholding belief about Attainability. I show that Attainability should be read as a principle of willing simpliciter and that these objections do not withstand critical scrutiny. Kant’s critics, therefore, will need either to sharpen their objections or seek alternatives elsewhere.