Reinhold: Letters on the Kantian Philosophy

By means of proofs whose thoroughness you yourself, dear friend, will examine in due time, the Critique of Reason [118] has shown “that it is just as impossible for speculative reason to demonstrate the immortality of the soul as it is for it to demonstrate the existence of the deity,” and “that practical reason, on the contrary, through the same postulates by which it presupposes a highest principle of moral and natural laws, also makes necessary the expectation of a future world in which morality and happiness must stand in most perfect harmony according to the determination of that highest principle.” In my next letter, I shall more closely elucidate this result, which contains the final and forever decisive answer to the second main question with which our speculative philosophy has occupied itself until now. In the current letter, I mention it merely as a sample of the most striking fruitfulness [119] belonging to the moral ground of cognition and of the admirable simplicity that religious conviction obtains through it. Assuming the correctness of this cited result, we not only gain a rational system of pure theology that grounds the entire doctrine of the deity on a single, first, and unshakeable principle of rational faith – which was the subject of discussion in my previous letter – but we also gain a true and systematic philosophy of religion.