 Kant’s doctrine of the highest good is the foundation of his positive philosophy of religion. With the exception of some musings (esp. in the Critique of Pure Reason) about an assent driven by our regulative employment of purposiveness (cf. B426, A670/B698 and A826/B854), the path to religion is through the highest good. It is through this doctrine that Kant endorses belief in God’s existence as well as the immortality of the soul. It is also through this doctrine that Kant sets out what in the Religion he calls the Pure Rational System of Religion. Therein, Kant appraises Christian doctrines to determine whether or not they are conducive to our duty to pursue the highest good (see  section 3.6.4  and  section 3.7  below).