Not that Kant ever doubts the existence of “matter” and the external world; but he adds that we know nothing certain about them except that they exist. Our detailed knowledge is about their appearance, their phenomena, about the sensations which we have of them. Idealism does not mean, as the man in the street thinks, that nothing exists outside the perceiving subject; but that a goodly part of every object is created by the forms of perception and understanding: we know the object as transformed into idea; what it is before being so transformed we cannot know. Science, after all, is naïve; it supposes that it is dealing with things in themselves, in their full-blooded external and uncorrupted reality; philosophy is a little more sophisticated, and realizes that the whole material of science consists of sensations, perceptions and conceptions, rather than of things. “Kant’s greatest merit,” says Schopenhauer, “is the distinction of the phenomenon from the thing-in-itself.”22
It follows that any attempt, by either science or religion, to say just what the ultimate reality is, must fall back into mere hypothesis; “the understanding can never go beyond the limits of sensibility.”23 Such transcendental science loses itself in “antinomies,” and such transcendental theology loses itself in “paralogisms.” It is the cruel function of “transcendental dialectic” to examine the validity of these attempts of reason to escape from the enclosing circle of sensation and appearance into the unknowable world of things “in themselves.”
Antinomies are the insoluble dilemmas born of a science that tries to overleap experience. So, for example, when knowledge attempts to decide whether the world is finite or infinite in space, thought rebels against either supposition: beyond any limit, we are driven to conceive something further, endlessly; and yet infinity is itself inconceivable. Again: did the world have a beginning in time? We cannot conceive eternity; but then, too, we cannot conceive any point in the past without feeling at once that before that, something was. Or has that chain of causes which science studies, a beginning, a First Cause? Yes, for an endless chain is inconceivable; no, for a first cause uncaused is inconceivable as well. Is there any exit from these blind alleys of thought? There is, says Kant, if we remember that space, time and cause are modes of perception and conception, which must enter into all our experience, since they are the web and structure of experience; these dilemmas arise from supposing that space, time and cause are external things independent of perception. We shall never have any experience which we shall not interpret in terms of space and time and cause; but we shall never have any philosophy if we forget that these are not things, but modes of interpretation and understanding.
So with the paralogisms of “rational” theology—which attempts to prove by theoretical reason that the soul is an incorruptible substance, that the will is free and above the law of cause and effect, and that there exists a “necessary being,” God, as the presupposition of all reality. Transcendental dialectic must remind theology that substance and cause and necessity are finite categories, modes of arrangement and classification which the mind applies to sense-experience, and reliably valid only for the phenomena that appear to such experience; we cannot apply these conceptions to the noumenal (or merely inferred and conjectural) world. Religion cannot be proved by theoretical reason.
So the first Critique ends. One could well imagine David Hume, uncannier Scot than Kant himself, viewing the results with a sardonic smile. Here was a tremendous book, eight hundred pages long; weighted beyond bearing, almost, with ponderous terminology; proposing to solve all the problems of metaphysics, and incidentally to save the absoluteness of science and the essential truth of religion. What had the book really done? It had destroyed the naïve world of science, and limited it, if not in degree, certainly in scope,—and to a world confessedly of mere surface and appearance, beyond which it could issue only in farcical “antinomies”; so science was “saved”! The most eloquent and incisive portions of the book had argued that the objects of faith—a free and immortal soul, a benevolent creator—could never be proved by reason; so religion was “saved”! No wonder the priests of Germany protested madly against this salvation, and revenged themselves by calling their dogs Immanuel Kant.24
And no wonder that Heine compared the little professor of Königsberg with the terrible Robespierre; the latter had merely killed a king, and a few thousand Frenchmen—which a German might forgive; but Kant, said Heine, had killed God, had undermined the most precious arguments of theology. “What a sharp contrast between the outer life of this man, and his destructive, world-convulsing thoughts! Had the citizens of Königsberg surmised the whole significance of those thoughts, they would have felt a more profound awe in the presence of this man than in that of an executioner, who merely slays human beings. But the good people saw in him nothing but a professor of philosophy; and when at the fixed hour he sauntered by, they nodded a friendly greeting, and set their watches.”25
Was this caricature, or revelation?
IV. The Critique of Practical Reason
If religion cannot be based on science and theology, on what then? On morals. The basis in theology is too insecure; better that it should be abandoned, even destroyed; faith must be put beyond the reach or realm of reason. But therefore the moral basis of religion must be absolute, not derived from questionable sense-experience or precarious inference; not corrupted by the admixture of fallible reason; it must be derived from the inner self by direct perception and intuition. We must find a universal and necessary ethic; à priori principles of morals as absolute and certain as mathematics. We must show that “pure reason can be practical; i.e., can of itself determine the will independently of anything empirical,”26 that the moral sense is innate, and not derived from experience. The moral imperative which we need as the basis of religion must be an absolute, a categorical, imperative.
Now the most astounding reality in all our experience is precisely our moral sense, our inescapable feeling, in the face of temptation, that this or that is wrong. We may yield; but the feeling is there nevertheless. Le matin je fais des projets, et le soir je fais des sottises;27 but we know that they are sottises, and we resolve again. What is it that brings the bite of remorse, and the new resolution? It is the categorical imperative in us, the unconditional command of our conscience, to “act as if the maxim of our action were to become by our will a universal law of nature.”28 We know, not by reasoning, but by vivid and immediate feelings, that we must avoid behavior which, if adopted by all men, would render social life impossible. Do I wish to escape from a predicament by a lie? But “while I can will the lie, I can by no means will that lying should be a universal law. For with such a law there would be no promises at all.”29 Hence the sense in me, that I must not lie, even if it be to my advantage. Prudence is hypothetical; its motto is, Honesty when it is the best policy; but the moral law in our hearts is unconditional and absolute.