 But, second, if “we can cognize of things a priori only what we ourselves have put into them,” then we cannot have a priori knowledge about things whose existence and nature are entirely independent of the human mind, which Kant calls things in themselves (Bxviii). In his words: “[F]rom this deduction of our faculty of cognizing a priori […] there emerges a very strange result […], namely that with this faculty we can never get beyond the boundaries of possible experience, […and] that such cognition reaches appearances only, leaving the thing in itself as something actual for itself but uncognized by us” (Bxix–xx). That is, Kant’s constructivist foundation for scientific knowledge restricts science to the realm of appearances and implies that transcendent metaphysics – i.e., a priori knowledge of things in themselves that transcend possible human experience – is impossible. In the Critique Kant thus rejects the insight into an intelligible world that he defended in the Inaugural Dissertation, and he now claims that rejecting knowledge about things in themselves is necessary for reconciling science with traditional morality and religion. This is because he claims that belief in God, freedom, and immortality have a strictly moral basis, and yet adopting these beliefs on moral grounds would be unjustified if we could know that they were false. “Thus,” Kant says, “I had to deny knowledge in order to make room for faith” (Bxxx). Restricting knowledge to appearances and relegating God and the soul to an unknowable realm of things in themselves guarantees that it is impossible to disprove claims about God and the freedom or immortality of the soul, which moral arguments may therefore justify us in believing. Moreover, the determinism of modern science no longer threatens the freedom required by traditional morality, because science and therefore determinism apply only to appearances, and there is room for freedom in the realm of things in themselves, where the self or soul is located. We cannot know (theoretically) that we are free, because we cannot know anything about things in themselves. But there are especially strong moral grounds for the belief in human freedom, which acts as “the keystone” supporting other morally grounded beliefs (5:3–4). In this way, Kant replaces transcendent metaphysics with a new practical science that he calls the metaphysics of morals. It thus turns out that two kinds of metaphysics are possible: the metaphysics of experience (or nature) and the metaphysics of morals, both of which depend on Kant’s Copernican revolution in philosophy.