Kant’s account of the idea of God in the first Critique prefigures but does not imply a theism. It is in his ethical philosophy that this idea is given a theistic interpretation, and that the postulation (or fideic affirmation) of God’s existence, along with immortality, is practically justified as a condition of the possibility of the summum bonum. This paper argues that Kant’s reasoning from his initially austere conception of morality to the summum bonum and to immortality and God’s existence (...) lacks compelling logic. It also argues that Kant’s practical justification of faith, amounting to no more than the claim that practical reason explicates its own inherent need and satisfies this need by faith, fails to satisfy the demand of religious consciousness for an ontology of reason that includes an account of the grounding of reason in what it postulates. (shrink)