Why is there no Kantian duty to believe in God and Immortality?

Kant emphatically denies that we stand under a moral duty to believe in God and (our) immortality. This essay examines how this denial could be consistent with his view that we have a moral duty to promote the highest good and that promoting the highest good requires us to adopt these beliefs. I argue that the key to understanding Kant's denial of a duty to believe lies in his view that not every rational requirement has the special, especially dignified normative necessity of duty. Moral duties express objective reasons that have unconditional universal validity – these reasons apply to all rational beings. By contrast, since the reasons for believing in God and immortality are grounded in the conative and cognitive limitations of finite reason, these reasons have a subjectively rational character and a limited degree of universal validity; they apply only to all finitely rational creatures. This is why Kant can consistently claim that we are rationally but not morally required to believe in God and immortality, even though we are morally required to promote the highest good and cannot rationally comply with this duty without adopting theistic beliefs.