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

by Norman Kemp Smith

Secondly, we cannot proceed on the assumption that Kant’s maturest teaching comes where, had the Critique been a unitary work, composed upon a definite and previously thought out plan, we should naturally expect to find it, namely, in its concluding portions. The teaching of much of the Dialectic, especially in its account of the nature of the phenomenal world and of its relation to the knowing mind, is only semi-Critical. This is also true of Kant’s Introduction to the Critique. Introductions are usually written last; and probably Kant’s Introduction was written after the completion of the Aesthetic, of the Dialectic, and of the Analytic in its earlier forms. But it bears all the signs of having been composed prior to the working out of several of his most characteristic doctrines in the central parts of the Analytic.

Thus both Kant’s introductory statements of the aims and purposes of the Critique, and his application of his results in the solution of metaphysical problems, fail to represent in any adequate fashion the new and revolutionary principles to which he very gradually but successfully worked his way. The key to the Critique is given in the central portions of the Analytic, especially in the Deduction of the Categories. The other parts of the Critique reveal the Critical doctrines only as gradually emerging from the entangling influence of pre-Critical assumptions. Their teaching has to be radically remodelled before they can be made to harmonise with what, in view both of their intrinsic character and of the corresponding alterations in the second edition, must be regarded as Kant’s maturest utterances.

This was a task which Kant never himself attempted. For no sooner had he attained to comparative clearness in regard to his new Critical principles and briefly expounded them in the Analytic of the first edition, than he hastened to apply them in the spheres of morality, aesthetics, and teleology. When the Critique appeared in 1781 he was fifty-seven years of age; and he seems to have feared that if he allowed these purely theoretical problems, which had already occupied his main attention for “at least twelve years,” to detain him longer, he would be debarred from developing and placing on permanent record the new metaphysics of ethics which, as the references in the first Critique show, had already begun to shape itself in his mind. To have expended further energy upon the perfecting of his theoretical philosophy would have endangered its own best fruits. Even the opportunity in 1787 of a second edition of the Critique he used very sparingly, altering or adding only where occasional current criticism—his puzzled contemporaries having still for the most part maintained a discreet silence—had clearly shown that his modes of exposition were incomplete or misleading.

II. HISTORICAL

KANT’S RELATION TO HUME AND TO LEIBNIZ

Kant’s manner of formulating his fundamental problem—How are synthetic a priori judgments possible?—may well seem to the modern reader to imply an unduly scholastic and extremely rationalistic method of approach. Kant’s reasons for adopting it have, unfortunately, been largely obscured, owing to the mistaken interpretation which has usually been given to certain of his personal utterances. They have been supposed to prove that the immediate occasion of the above formula was Hume’s discussion of the problem of causality in the Enquiry into the Human Understanding. Kant, it is argued, could not have been acquainted with Hume’s earlier and more elaborate Treatise on Human Nature, of which there was then no translation; and his references to Hume must therefore concern only the later work.

Vaihinger has done valuable service in disputing this reading of Kant’s autobiographical statements. Kant does not himself make direct mention of the Enquiry, and the passages in the Critique and in the Prolegomena[9] in which Hume’s teaching is under consideration seem rather to point to the wider argument of the Treatise. This is a matter of no small importance; for if Vaihinger’s view can be established, it will enable us to appreciate, in a manner otherwise impossible, how Kant should have come to regard the problem of a priori synthesis as being the most pressing question in the entire field of speculative philosophy.

The essential difference between the Treatise and the Enquiry, from the standpoint of their bearing upon Critical issues, lies in the wider scope and more radical character of the earlier work. The Enquiry discusses the problem of causality only in the form in which it emerges in particular causal judgments, i.e. as to our grounds for asserting that this or that effect is due to this or that cause. In the Treatise, Hume raises the broader question as to our right to postulate that events must always be causally determined. In other words, he there questions the validity of the universal causal principle, that whatever begins to exist must have a cause of existence; and he does so on the explicit ground that it demands as necessary the connecting of two concepts, that of an event and that of an antecedent cause, between which no connection of any kind can be detected by the mind. The principle, that is to say, is not self-evident; it is synthetic. The concept of an event and the concept of a cause are quite separate and distinct ideas. Events can be conceived without our requiring to think antecedent events upon which they are dependent. Nor is the principle capable of demonstration. For if it be objected that in questioning its validity we are committing ourselves to the impossible assertion that events arise out of nothing, such argument is only applicable if the principle be previously granted. If events do not require a cause, it is as little necessary to seek their source in a generation out of nothing as in anything positive. Similarly, when it is argued that as all the parts of time and space are uniform, there must be a cause determining an event to happen at one moment and in one place rather than at some other time or place, the principle is again assumed. There is no greater difficulty in supposing the time and place to be fixed without a cause than in supposing the existence to be so determined. The principle, Hume concludes, is non-rational in character. It is an instrument useful for the organisation of experience; and for that reason nature has determined us to its formation and acceptance. Properly viewed, it expresses a merely instinctive belief, and is explicable only in the naturalistic manner of our other propensities, as necessary to the fulfilling of some practical need. “Nature has determined us to judge as well as to breathe and feel.”

From this naturalistic position Hume makes a no less vigorous attack upon the empirical philosophies which profess to establish general principles by inductive inference from the facts of experience. If the principles which lie at the basis of our experience are non-rational in character, the same must be true of our empirical judgments. They may correctly describe the uniformities that have hitherto occurred in the sequences of our sensations, and may express the natural expectations to which they spontaneously give rise; but they must never be regarded as capable of serving as a basis for inference. In eliminating a priori principles, and appealing exclusively to sense-experience, the empiricist removes all grounds of distinction between inductive inference and custom-bred expectation. And since from this standpoint the possibility of universal or abstract concepts—so Hume argues—must also be denied, deductive inference must likewise be eliminated from among the possible instruments at the disposal of the mind. So-called inference is never the source of our beliefs; it is our fundamental natural beliefs, as determined by the constitution of our nature in its reaction upon external influences, that generate those expectations which, however they may masquerade in logical costume, have as purely natural a source as our sensations and feelings. Such, briefly and dogmatically stated, is the sum and substance of Hume’s teaching.[10]

Now it was these considerations that, as it would seem, awakened Kant to the problem of a priori synthesis. He was, and to the very last remained, in entire agreement with Hume’s contention that the principle of causality is neither self-evident nor capable of logical demonstration, and he at once realised that what is true of this principle must also hold of all the other principles fundamental to science and philosophy. Kant further agreed that inductive inference from the data of experience is only possible upon the prior acceptance of rational principles independently established; and that we may not, therefore, look to experience for proof of their validity. Thus with the rejection of self-evidence as a feature of the a priori, and with the consequent admission of its synthetic character, Kant is compelled to acquiesce in the inevitableness of the dilemma which Hume propounds. Either Hume’s sceptical conclusions must be accepted, or we must be able to point to some criterion which is not subject to the defects of the rationalist and empirical methods of proof, and which is adequate to determine the validity or invalidity of general principles. Is there any such alternative? Such is Kant’s problem as expressed in the formula: How are synthetic a priori judgments possible?