Kant: Religion within the Boundaries of Mere Reason And Other Writings

As the title, Religion within the Boundaries of Mere Reason, rightly suggests, Immanuel Kant's religious thought is strongly rationalistic. In this Kant belongs to an important current of eighteenth-century thought – but with a difference. Rationalistic religious thought of the period, in Germany as in Britain, typically proposed to base religious belief on metaphysical proofs of the existence of God. Kant himself propounded and defended such a demonstration of divine existence in The Only Possible Ground of Proof for a Demonstration of God's Existence (1763), a work of his earlier, “precritical” period. In the Critique of Pure Reason (1781), however, which inaugurated the “critical” period to which all the works collected in the present volume belong, Kant criticized traditional attempts at metaphysical demonstration of the existence of God, and argued that the nature and intrinsic limits of human thought and knowledge preclude any such demonstration. Such a critique might be expected to support atheism, but that was not Kant's intent. On the contrary, he argued that any metaphysical demonstration of the non-existence of God is equally precluded by the limits of reason. In a famous phrase, he declared that he “had to deny knowledge, in order to make room for faith” (B XXX).

The faith Kant has in mind is a purely rational faith, but it is grounded in practical (action-guiding, moral) reason rather than in theoretical reason. In Kant's view the inability of our theoretical faculties to prove the truth or falsity of religious claims leaves room for our practical reason to determine our religious stance. He welcomes this because he thinks it crucial for religion to be controlled by moral considerations.

Both in the Critique of Pure Reason and more fully in the Critique of Practical Reason (1788), Kant argues that the needs of morality demand and justify a sort of faith in the existence of God; he gives related arguments for believing in human immortality and affirming the freedom of the human will. We will touch on Kant's views on free will below; the arguments for belief in God and immortality both turn on claims that morality demands that we set ourselves certain ends, and that we therefore need, morally, to believe in the possible attainment of those ends. One such end is the perfection of our own virtue.