PREFACE TO THE SECOND EDITION

I SHALL again give a brief explanatory paraphrase, before proceeding to detailed comment. The main points of the preface of the first edition are repeated. “Metaphysics soars above all teaching of experience, and rests on concepts only. In it reason has to be her own pupil.”[110] But Kant immediately proceeds to a further point. That logic should have attained the secure method of science is due to its limitation to the mere a priori form of knowledge. For metaphysics this is far more difficult, since it “has to deal not with itself alone, but also with objects.”[111]

The words which I have italicised form a very necessary correction of the first edition preface, according to which the Critique would seem to “treat only of reason and its pure thinking.” A further difference follows. The second edition preface, in thus emphasising the objective aspect of the problem, is led to characterise in a more complete manner the method to be followed in the Critical enquiry. How can the Critique, if it is concerned, as both editions agree in insisting, only with the a priori which originates in human reason, solve the specifically metaphysical problem, viz. that of determining the independently real? How can an idea in us refer to, and constitute knowledge of, an object? The larger part of the preface to the second edition is devoted to the Critical solution of this problem. The argument of the Dialectic is no longer emphasised at the expense of the Analytic.

Kant points out that as a matter of historical fact each of the two rational sciences, mathematics and physics, first entered upon the assured path of knowledge by a sudden revolution, and by the adoption of a method which in its general characteristics is common to both. This method consists, not in being led by nature as in leading-strings, but in interrogating nature in accordance with what reason produces on its own plan. The method of the geometrician does not consist in the study of figures presented to the senses. That would be an empirical (in Kant’s view, sceptical) method. Geometrical propositions could not then be regarded as possessing universality and necessity. Nor does the geometrician employ a dogmatic method, that of studying the mere conception of a figure. By that means no new knowledge could ever be attained. The actual method consists in interpreting the sensible figures through conceptions that have been rigorously defined, and in accordance with which the figures have been constructively generated. The first discovery of this method, by Thales or some other Greek, was “far more important than the discovery of the passage round the celebrated Cape of Good Hope.”[112]

Some two thousand years elapsed before Galileo formulated a corresponding method for physical science. He relied neither on mere observation nor on his own conceptions. He determined the principles according to which alone concordant phenomena can be admitted as laws of nature, and then by experiment compelled nature to answer the questions which these principles suggest. Here again the method is neither merely empirical nor purely dogmatic. It possesses the advantages of both.

Metaphysics is ripe for a similar advance. It must be promoted to the rank of positive science by the transforming power of an analogous method. The fundamental and distinguishing characteristic of mathematical and physical procedure is the legislative power to which reason lays claim. Such procedure, if generalised and extended, will supply the required method of the new philosophy. Reason must be regarded as self-legislative in all the domains of our possible knowledge. Objects must be viewed as conforming to human thought, not human thought to the independently real. This is the “hypothesis” to which Kant has given the somewhat misleading title, “Copernican.”[113] The method of procedure which it prescribes is, he declares, analogous to that which was followed by Copernicus, and will be found to be as revolutionary in its consequences. In terms of this hypothesis a complete and absolutely certain metaphysics, valid now and for all time, can be created at a stroke. The earliest and oldest enterprise of the human mind will achieve a new beginning. Metaphysics, the mother of all the sciences, will renew her youth, and will equal in assurance, as she surpasses in dignity, the offspring of her womb.

From this new standpoint Kant develops phenomenalism on rationalist lines. He professes to prove that though our knowledge is only of appearances, it is conditioned by a priori principles. His “Copernican hypothesis,” so far from destroying positive science, is, he claims, merely a philosophical extension of the method which it has long been practising. Since all science worthy of the name involves a priori elements, it can be accounted for only in terms of the new hypothesis. Only if objects are regarded as conforming to our forms of intuition, and to our modes of conception, can they be anticipated by a priori reasoning. Science can be a priori just because, properly understood, it is not a rival of metaphysics, and does not attempt to define the absolutely real.

But such a statement at once suggests what may at first seem a most fatal objection. Though the new standpoint may account for the a priori in experience and science, it can be of no avail in metaphysics. If the a priori concepts have a mental origin, they can have no validity for the independently real. If we can know only what we ourselves originate, things in themselves must be unknown, and metaphysics must be impossible. But in this very consequence the new hypothesis first reveals its full advantages. It leads to an interpretation of metaphysics which is as new and as revolutionary[114] as that which it gives to natural science. Transcendent metaphysics is indeed impossible, but in harmony with man’s practical and moral vocation, its place is more efficiently taken by an immanent metaphysics on the one hand, and by a metaphysics of ethics on the other. Together these constitute the new and final philosophy which Kant claims to have established by his Critical method. Its chief task is to continue “that noblest enterprise of antiquity,”[115] the distinguishing of appearances from things in themselves. The unconditioned is that which alone will satisfy speculative reason; its determination is the ultimate presupposition of metaphysical enquiry. But so long as the empirical world is regarded as true reality, totality or unconditionedness cannot possibly be conceived—is, indeed, inherently self-contradictory. On the new hypothesis there is no such difficulty. By the proof that things in themselves are unknowable, a sphere is left open within which the unconditioned can be sought. For though this sphere is closed to speculative reason, the unconditioned can be determined from data yielded by reason in its practical activity. The hypothesis which at first seems to destroy metaphysics proves on examination to be its necessary presupposition. The “Copernican hypothesis” which conditions science will also account for metaphysics properly conceived.

Upon this important point Kant dwells at some length. Even the negative results of the Critique are, he emphasises, truly positive in their ultimate consequences. The dogmatic extension of speculative reason really leads to the narrowing of its employment, for the principles of which it then makes use involve the subjecting of things in themselves to the limiting conditions of sensibility. All attempts to construe the unconditioned in terms that will satisfy reason are by such procedure ruled out from the very start. To demonstrate this is the fundamental purpose and chief aim of the Critique. Space and time are merely forms of sensuous intuition; the concepts of understanding can yield knowledge only in their connection with them. Though the concepts in their purity possess a quite general meaning, this is not sufficient to constitute knowledge. The conception of causality, for instance, necessarily involves the notion of time-sequence; apart from time it is the bare, empty, and entirely unspecified conception of a sufficient ground. Similarly, the category of substance signifies the permanent in time and space; as a form of pure reason it has a quite indefinite meaning signifying merely that which is always a subject and never a predicate. In the absence of further specification, it remains entirely problematic in its reference. The fact, however, that the categories of the understanding possess, in independence of sensibility, even this quite general significance is all-important. Originating in pure reason they have a wider scope than the forms of sense, and enable us to conceive, though not to gain knowledge of, things in themselves.[116] Our dual nature, as being at once sensuous and supersensuous, opens out to us the apprehension of both.

Kant illustrates his position by reference to the problem of the freedom of the will. As thought is wider than sense, and reveals to us the existence of a noumenal realm, we are enabled to reconcile belief in the freedom of the will with the mechanism of nature. We can recognise that within the phenomenal sphere everything without exception is causally determined, and yet at the same time maintain that the whole order of nature is grounded in noumenal conditions. We can assert of one and the same being that its will is subject to the necessity of nature and that it is free—mechanically determined in its visible actions, free in its real supersensible existence. We have, indeed, no knowledge of the soul, and therefore cannot assert on theoretical grounds that it possesses any such freedom. The very possibility of freedom transcends our powers of comprehension. The proof that it can at least be conceived without contradiction is, however, all-important. For otherwise no arguments from the nature of the moral consciousness could be of the least avail; before a palpable contradiction every argument is bound to give way. Now, for the first time, the doctrine of morals and the doctrine of nature can be independently developed, without conflict, each in accordance with its own laws. The same is true in regard to the existence of God and the immortality of the soul. By means of the Critical distinction between the empirical and the supersensible worlds, these conceptions are now for the first time rendered possible of belief. “I had to remove knowledge, in order to make room for belief.”[117] “This loss affects only the monopoly of the schools, in no respect the interests of humanity.”[118]

Lastly, Kant emphasises the fact that the method of the Critique must be akin to that of dogmatism. It must be rational a priori. To adopt any other method of procedure is “to shake off the fetters of science altogether, and thus to change work into play, certainty into opinion, philosophy into philodoxy.”[119] And Kant repeats the claims of the preface of the first edition as to the completeness and finality of his system. “This system will, as I hope, maintain through the future this same unchangeableness.”[120]

Logic.[121]—For Kant’s view of the logic of Aristotle as complete and perfect, cf. below, pp. 184-5. Kant compares metaphysics to mathematics and physics on the one hand, and to formal logic on the other. The former show the possibility of attaining to the secure path of science by a sudden and single revolution; the latter demonstrates the possibility of creating a science complete and entire at a stroke. Thanks to the new Critical method, metaphysics may be enabled, Kant claims, to parallel both achievements at once.

Theoretical and practical reason.[122]—Such comment as is necessary upon this distinction is given below. Cf. p. 569 ff.

Hitherto it has been supposed that all knowledge must conform to the objects.[123]—This statement is historically correct. That assumption did actually underlie one and all of the pre-Kantian philosophies. At the same time, it is true that Kant’s phenomenalist standpoint is partially anticipated by Hume, by Malebranche and by Leibniz, especially by the first named. Hume argues that to condemn knowledge on the ground that it can never copy or truly reveal any external reality is to misunderstand its true function. Our sense perceptions and our general principles are so determined by nature as to render feasible only a practical organisation of life. When we attempt to derive from them a consistent body of knowledge, failure is the inevitable result.[124] Malebranche, while retaining the absolutist view of conceptual knowledge, propounds a similar theory of sense-perception.[125] Our perceptions are, as he shows, permeated through and through, from end to end, with illusion. Such illusions justify themselves by their practical usefulness, but they likewise prove that theoretical insight is not the purpose of our sense-experience. Kant’s Copernican hypothesis consists in great part of an extension of this view to our conceptual, scientific knowledge. But he differs both from Malebranche and from Hume in that he develops his phenomenalism on rationalist lines. He professes to show that though our knowledge is only of the phenomenal, it is conditioned by a priori principles. The resulting view of the distinction between appearance and reality has kinship with that of Leibniz.[126] The phenomena of science, though only appearances, are none the less bene fundata. Our scientific knowledge, though not equivalent to metaphysical apprehension of the ultimately real, can be progressively developed by scientific methods.

The two “parts” of metaphysics.[127]—Kant is here drawing the important distinction, which is one result of his new standpoint, between immanent and transcendent metaphysics. It is unfortunate that he does not do so in a more explicit manner, with full recognition of its novelty and of its far-reaching significance. Many ambiguities in his exposition here and elsewhere would then have been obviated.[128]

The unconditioned which Reason postulates in all things by themselves, by necessity and by right.[129]—Points are here raised the discussion of which must be deferred. Cf. below, pp. 429-31, 433-4, 558-61.

The Critique is a treatise on method, not a system of the science itself.[130]—Cf. A xv.; B xxxvi.; and especially A 11 = B 24, below pp. 71-2.

The Copernican hypothesis.[131]—Kant’s comparison of his new hypothesis to that of Copernicus has generally been misunderstood. The reader very naturally conceives the Copernican revolution in terms of its main ultimate consequence, the reduction of the earth from its proud position of central pre-eminence. But that does not bear the least analogy to the intended consequences of the Critical philosophy. The direct opposite is indeed true. Kant’s hypothesis is inspired by the avowed purpose of neutralising the naturalistic implications of the Copernican astronomy. His aim is nothing less than the firm establishment of what may perhaps be described as a Ptolemaic, anthropocentric metaphysics. Such naturalistic philosophy as that of Hume may perhaps be described as Copernican, but the Critical philosophy, as humanistic, has genuine kinship with the Greek standpoint.

Even some of Kant’s best commentators have interpreted the analogy in the above manner.[132] It is so interpreted by T. H. Green[133] and by J. Hutchison Stirling.[134] Caird in his Critical Philosophy of Kant makes not the least mention of the analogy, probably for the reason that while reading it in the same fashion as Green, he recognised the inappropriateness of the comparison as thus taken. The analogy is stated in typically ambiguous fashion by Lange[135] and by Höffding.[136] S. Alexander, while very forcibly insisting upon the Ptolemaic character of the Kantian philosophy, also endorses this interpretation in the following terms:

As the second edition preface is not covered by the published volumes of Vaihinger’s Commentary, the point has not been taken up by him.

Now Kant’s own statements are entirely unambiguous and do not justify any such interpretation as that of Green and Alexander. As it seems to me, they have missed the real point of the analogy. The misunderstanding would never have been possible save for our neglect of the scientific classics. Kant must have had first-hand acquaintance with Copernicus’ De Revolutionibus, and the comparison which he draws assumes similar knowledge on the part of his readers. Copernicus by his proof of the “hypothesis” (his own term) of the earth’s motion sought only to achieve a more harmonious ordering of the Ptolemaic universe. And as thus merely a simplification of the traditional cosmology, his treatise could fittingly be dedicated to the reigning Pope. The sun upon which our terrestrial life depends was still regarded as uniquely distinct from the fixed stars; and our earth was still located in the central region of a universe that was conceived in the traditional manner as being single and spherical. Giordano Bruno was the first, a generation later, to realise the revolutionary consequences to which the new teaching, consistently developed, must inevitably lead. It was he who first taught what we have now come to regard as an integral part of Copernicus’ revolution, the doctrine of innumerable planetary systems side by side with one another in infinite space.

Copernicus’ argument starts from the Aristotelian principle of relative motion. To quote Copernicus’ exact words:

The apparently objective movements of the fixed stars and of the sun are mere appearances, due to the projection of our own motion into the heavens.

Now it is this doctrine, and this doctrine alone, to which Kant is referring in the passages before us, namely, Copernicus’ hypothesis of a subjective explanation of apparently objective motions. And further, in thus comparing his Critical procedure to that of Copernicus, he is concerned more with the positive than with the negative consequences of their common hypothesis. For it is chiefly from the point of view of the constructive parts of the Aesthetic, Analytic, and Dialectic that the comparison is formulated. By means of the Critical hypothesis Kant professes on the one hand to account for our scientific knowledge, and on the other to safeguard our legitimate metaphysical aspirations. The spectator projects his own motion into the heavens; human reason legislates for the domain of natural science. The sphere of the fixed stars is proved to be motionless; things in themselves are freed from the limitations of space and time. “Copernicus dared, in a manner contradictory of the senses but yet true, to seek the observed movements, not in the heavenly bodies, but in the spectator.”[140]

In view of Kant’s explicit elimination of all hypotheses from the Critique[141] the employment of that term would seem to be illegitimate. He accordingly here states that though in the Preface his Critical theory is formulated as an hypothesis only, in the Critique itself its truth is demonstrated a priori.

Distinction between knowing and thinking.[142]—Since according to Critical teaching the limits of sense-experience are the limits of knowledge, the term knowledge has for Kant a very limited denotation, and leaves open a proportionately wide field for what he entitles thought. Though things in themselves are unknowable, their existence may still be recognised in thought.