A Commentary to Kant's 'Critique of Pure Reason'

by Norman Kemp Smith

But this does not close Kant’s treatment of metaphysical hypotheses. He proceeds to develop a doctrine which, in its fearless confidence in the truth of Critical teaching, is the worthy outcome of his abiding belief in the value of a “sceptical method.”[1645] As Reason is by its very nature dialectical, outside opponents are not those from whom we have most to fear. Their objections are really derived from a source which lies in ourselves, and until these have been traced to their origin, and destroyed from the root upwards, we can expect no lasting peace. Our duty, therefore, is to encourage our doubts, until by the very luxuriance of their growth they enable us to discover the hidden roots from which they derive their perennial vitality.

“External tranquillity is a mere illusion. The germ of these objections, which lies in the nature of human Reason, must be rooted out. But how can we uproot it, unless we give it freedom, nay, nourishment, to send out shoots so that it may discover itself to our eyes, and that we may then destroy it together with its root? Therefore think out objections which have never yet occurred to any opponent; lend him, indeed, your weapons, or grant him the most favourable position which he could possibly desire. You have nothing to fear in all this, but much to hope for; you may gain for yourselves a possession which can never again be contested.”[1646]

In this campaign to eradicate doubt by following it out to its furthermost limits, the hypotheses of pure Reason, “leaden weapons though they be, since they are not steeled by any law of experience,” are an indispensable part of our equipment. For though hypotheses are useless for the establishment of metaphysical propositions, they are, Kant teaches, both admirable and valuable for their defence. That is to say, their true metaphysical function is not dogmatic, but polemical. They are weapons of war to which we may legitimately resort for the maintenance of beliefs otherwise established. If, for instance, we have been led to postulate the immaterial, self-subsistent nature of the soul, and are met by the difficulty that experience would seem to prove that both the growth and the decay of our mental powers are due to the body, we can weaken this objection by formulating the hypothesis that the body is not the cause of our thinking, but only a restrictive condition of it, peculiar to our present state, and that, though it furthers our sensuous and animal faculties, it acts as an impediment to our spiritual life. Similarly, to meet the many objections against belief in the eternal existence of a finite being whose birth depends upon contingencies of all kinds, such as the food supply, the whims of government, or even vice, we can adduce the transcendental hypothesis that life has neither beginning in birth nor ending in death, the entire world of sense being but an image due to our present mode of knowledge, an image which like a dream has in itself no objective reality. Such hypotheses are not, indeed, even Ideas of Reason, but simply concepts invented to show that the objections which are raised depend upon the false assumption that the possibilities have been exhausted, and that the mere laws of nature comprehend the whole field of possible existences. These hypotheses at least suffice to reveal the uncertain character of the doubts which assail us in our practical beliefs.

”[Transcendental hypotheses] are nothing but private opinions. Nevertheless, we cannot properly dispense with them as weapons against the misgivings which are apt to occur; they are necessary even to secure our inner tranquillity. We must preserve to them this character, carefully guarding against the assumption of their independent authority or absolute validity, since otherwise they would drown Reason in fictions and delusions.”[1647]

We may now return to A 642-68 = B 670-96. The teaching of this section is extremely self-contradictory, wavering between a subjective and an objective interpretation of the Ideas of Reason. The probable explanation is that Kant is here recasting older material, and leaves standing more of his earlier solutions than is consistent with his final conclusions. We can best approach the discussion by considering Kant’s statements in A 645 = B 673 and in A 650 ff. = B 678 ff. They expound, though unfortunately in the briefest terms, a point of view which Idealism has since adopted as fundamental. Kant himself, very strangely, never develops its consequences at any great length.[1648] The Idea, which Reason follows in the exercise of its sole true function, the systematising of the knowledge supplied by the understanding, is that of a unity in which the thought of the whole precedes the knowledge of its parts, and contains the conditions according to which the place of every part and its relation to the other parts are determined a priori. This Idea specialises itself in various forms, and in all of them directs the understanding to a knowledge that will be that of no mere aggregate but of a genuine system. Such concepts are not derived from nature; we interrogate nature according to them, and consider our knowledge defective so long as it fails to embody them. In A 650 = B 678 Kant further points out that this Idea of Reason does not merely direct the understanding to search for such unity, but also claims for itself objective reality. And he adds,

“...it is difficult to understand how there can be a logical principle by which Reason prescribes the unity of rules, unless we also presuppose a transcendental principle whereby such systematic unity is a priori assumed to be necessarily inherent in the objects.”

For how could we treat diversity in nature as only disguised unity, if we were also free to regard that unity as contrary to the actual nature of the real?

“Reason would then run counter to its own vocation, proposing as its aim an Idea quite inconsistent with the constitution of nature.”[1649]

Nor is our knowledge of the principle merely empirical, deduced from the unity which we find in contingent experience. On the contrary, there is an inherent and necessary law of Reason compelling us, antecedently to all specific experience, to look for such unity.