Towards the Highest Good: Endless Progress and Its Totality in Kant’s Moral Argument for the Postulate of Immortality

Abstract Kant’s moral proof of the postulate of immortality in the Critique of Practical Reason is often dismissed as a failed argument that trades on illicit conceptual shifts. I argue that Kant’s argument is more interesting and less problematic than is usually thought. I first examine its role in the second Critique’s Dialectic. I then point out that the standard interpretation, according to which the argument presupposes God’s intuitive grasp of the moral equivalence between the disposition to pursue holiness and its attainment, faces a number of philosophical and textual problems. I offer an alternative reading that avoids these problems. In particular, I stress the importance of Kant’s mathematized conception of the relationship between infinite progress towards an ideal goal and its attainment and argue that appealing to this conception allows Kant to meet a well-known criticism that his proof illegitimately substitutes the endless progress towards holiness for holiness itself.