Why Does Kant Think We Must Believe in the Immortal Soul?

Making sense of Kant’s claim that it is morally necessary for us to believe in the immortal soul is a historically fraught issue. Commentators typically reject it, or take one of two paths: they either restrict belief in the immortal soul to our subjective psychology, draining it of any substantive rational grounding; or make it out to be a rational necessity that morally interested beings must accept on pain of contradiction. Against these interpreters, I argue that on Kant’s view, belief in our immortality is necessary because it further determines and enriches the cognitive content contained in the concept of the highest good. Through this sharpened conceptual content, we acquire the resources to withstand theoretical skepticism about our moral vocation.