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

by Norman Kemp Smith

Detailed discussion of the Prefaces is not advisable. The problems which they raise can best be treated in the order in which they come up in the Critique itself. I shall dwell only on the minor incidental difficulties of the text, and on those features in Kant’s exposition which are peculiar to the Prefaces, or which seem helpful in the way of preliminary orientation. I shall first briefly restate the argument of the Preface to the first edition, and then add the necessary comment.

Human reason is ineradicably metaphysical. It is haunted by questions which, though springing from its very nature, none the less transcend its powers. Such a principle, for instance, as that of causality, in carrying us to more and more remote conditions, forces us to realise that by such regress our questions can never be answered. However far we recede in time, and however far we proceed in space, we are still no nearer to a final answer to our initial problems, and are therefore compelled to take refuge in postulates of a different kind, such, for instance, as that there must be a first unconditioned cause from which the empirical series of causes and effects starts, or that space is capable of existing as a completed whole. But these assumptions plunge reason in darkness and involve it in contradictions. They are the sources of all the troubles of the warring schools. Error lies somewhere concealed in them—the more thoroughly concealed that they surpass the limits of possible experience. Until such error has been detected and laid bare, metaphysical speculation must remain the idlest of all tasks.

In the latter part of the eighteenth century metaphysics had fallen, as Kant here states, into disrepute. The wonderful success with which the mathematical and natural sciences were being developed served only to emphasise by contrast the ineffectiveness of the metaphysical disciplines. Indifference to philosophy was the inevitable outcome, and was due, not to levity, but to the matured judgment of the age, which refused to be any longer put off with such pretended knowledge. But since the philosophical sciences aim at that knowledge which, if attainable, we should be least willing to dispense with, the failure of philosophy is really a summons to reason to take up anew the most difficult of all its tasks. It must once and for all determine either the possibility or the impossibility of metaphysics. It must establish

“...a tribunal which will assure to reason its lawful claims, and which will also be able to dismiss all groundless pretensions, not by despotic decrees, but in accordance with its own eternal and unalterable laws. This tribunal is no other than the Critique of Pure Reason.”[76] “Our age is, in especial degree, the age of criticism (Kritik), and to such criticism everything must submit. Religion, through its sanctity, and law-giving, through its majesty, may seek to exempt themselves from it. But they then awaken just suspicion, and cannot claim the sincere respect which reason accords only to that which has been able to sustain the test of free and open examination.”[77]

As has already been emphasised in the preceding historical sketch, Kant had learnt to trust the use of reason, and was a rationalist by education, temperament, and conviction. He here classifies philosophies as dogmatic and sceptical; and under the latter rubric he includes all empirical systems. ‘Empiricism’ and ‘scepticism’ he interprets as practically synonymous terms. The defect of the dogmatists is that they have not critically examined their methods of procedure, and in the absence of an adequate distinction between appearance and reality have interpreted the latter in terms of the former. The defect of the empiricists and sceptics is that they have misrepresented the nature of the faculty of reason, ignoring its claims and misreading its functions, and accordingly have gone even further astray than their dogmatic opponents. All knowledge worthy of the name is a priori knowledge. It possesses universality and necessity, and as such must rest on pure reason. Wherever there is science, there is an element of pure reason. Whether or not pure reason can also extend to the unconditioned is the question which decides the possibility of constructive metaphysics. This is what Kant means when he declares that the Critique is a criticism of the power of reason, in respect of all knowledge after which it may strive independently of experience. Pure reason is the subject-matter of the enquiry; it is also the instrument through which the enquiry is made.[78] Nothing empirical or merely hypothetical has any place in it, either as subject-matter or as method of argument.

From this position Kant draws several important consequences. First, since pure reason means that faculty whereby we gain knowledge independently of all experience, it can be isolated and its whole nature exhaustively determined. Indeed pure reason (Kant seeks to prove) is so perfect a unity that if “its principle” should be found insufficient to the solution of a single one of all the questions which are presented to it by its own nature, we should be justified in forthwith rejecting it as also incompetent to answer with complete certainty any one of the other questions. In metaphysics it must be either all or nothing,[79] either final and complete certainty or else absolute failure.

“While I am saying this I can fancy that I detect in the face of the reader an expression of indignation mingled with contempt at pretensions seemingly so arrogant and vainglorious; and yet they are incomparably more moderate than the claims of all those writers who on the lines of the usual programme profess to prove the simple nature of the soul or the necessity of a first beginning of the world.”[80]

In so doing they pretend to define realities which lie beyond the limits of possible experience; the Critique seeks only to deal with that faculty of reason which manifests itself to us within our own minds. Formal logic shows how completely and systematically the simple acts of reason can be enumerated. Aristotle created this science of logic complete at a stroke. Kant professes to have established an equally final metaphysics; and as logic is not a science proper, but rather a propaedeutic to all science, metaphysics, thus interpreted, is the only one of all the sciences which can immediately attain to such completeness.

“For it is nothing but the inventory of all our possessions through pure reason, systematically arranged. In this field nothing can escape us. What reason produces entirely out of itself cannot lie concealed, but is brought to light by reason itself immediately the common principle has been discovered.”[81]

Secondly, the Critique also claims certainty. With the removal of everything empirical, and the reduction of its subject-matter to pure reason, all mere opinion or hypothesis is likewise eliminated. Probabilities or hypotheses can have no place in a Critique of Pure Reason.[82] Everything must be derived according to a priori principles from pure conceptions in which there is no intermixture of experience or any special intuition.