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

by Norman Kemp Smith

Polemically, therefore, Kant’s formulation of the second Postulate is not without its advantages, though from the inner standpoint of Critical teaching it is altogether inadequate.

For comment upon A 226 = B 273, and upon the general teaching of this Postulate in its important bearing upon Kant’s phenomenalism, cf. above, pp. 318-19.

B 274-9.—Refutation of Idealism, cf. above, p. 308 ff.

Third Postulate.[1276]—In the opening sentence Kant draws the distinction which was lacking in his treatment of the first Postulate between ‘material’ and ‘formal’ modality. (No distinction, however, is drawn between the ‘formal’ possibility of the first Postulate and logical possibility, which consists in absence of contradiction.) It is with the former alone that we have to deal. As existence cannot be determined completely a priori, necessity can never be known from concepts, but only by reference to the actually given, in accordance with the universal principles that condition experience. Further, since such empirical necessity does not concern the existence of substances, but only the existence of their states, viewed as dynamically caused, the criterion of empirical necessity reduces to the second Analogy, viz. that everything which happens is determined by an antecedent empirical cause. This criterion does not extend beyond the field of possible experience, and even within that field applies only to those existences which can be viewed as effects, i.e. as events which come into existence in time, and of which therefore the causes are of the same temporal and conditioned character. The necessity is a hypothetical necessity; given an empirical event, it can always be legitimately viewed as necessitated by an antecedent empirical cause.

Kant introduces, reinterprets, and in this altered form professes to justify, four of the central principles of the Leibnizian metaphysics. In mundo non datur casus gives expression to the above empirical principle. Non datur fatum may be taken as meaning that natural (i.e. empirical) necessity is a conditioned and therefore comprehensible necessity, and is consequently not rightly described as blind. The other two principles, non datur saltus, and non datur hiatus connect with the principle of continuity already established in the Anticipations of Perception and in the second Analogy.

Kant’s further remarks reveal an uneasy feeling that he is neglecting to assign these principles to the pigeon-holes provided in his architectonic. The reader, he states, may easily do so for himself. That may be so, but only if the reader be permitted the same high-handed methods of adjustment that are here illustrated in Kant’s location of non datur fatum with the principles of modality.[1277]

In the next paragraph (A 230 = B 282) Kant suddenly, without warning or explanation, attaches to the term possibility a meaning altogether different from any yet assigned to it. He now takes it as equivalent to the absolutely or metaphysically possible. Combining this with the meanings previously given to it by Kant we obtain the following table:—

Possibility–	Logical: equivalent to absence of contradiction.
	Empirical: in the wider sense, equivalent to agreementwith the formal conditions of experience; in the narroweror stricter sense, involving in addition the capacityof being presented in sense-experience.
	Metaphysical: equivalent to absolute possibility, a conceptionnot of understanding but of Reason.

When this last meaning is given to the term, an entirely new set of problems arises, to the confusion of the reader who very properly continues to employ the term possibility in the empirical sense which, as Kant has been insisting, is alone legitimate. Kant has temporarily changed over to the standpoint of the metaphysical view which he has been criticising, and accordingly uses the term ‘possibility’ in the Leibnizian sense. Is Leibniz, he asks, justified in maintaining that the field of the possible is wider than the realm of the actual, and the latter in turn wider in extent than the necessary? In reply Kant accepts the metaphysical meaning assigned to the term ‘possibility,’ but restates the problem in Critical fashion. Do all things belong as appearances to the context of a single experience, or are other types of experience possible? Do other forms of intuition besides space and time, other forms of understanding besides the discursive through concepts, come within the range of the possible? These are questions which fall to be answered, not by the mere understanding, the sole function of which is empirical, but by Reason, which transcends the world of appearance.

Kant introduces these questions, as he is careful to state,[1278] only because they are currently believed to be within the competence of the understanding; and he now for the first time points out that possibility, in this sense, means absolute possibility, that which is independent of all limiting conditions, a meaning ruled out by the preceding treatment of the modal categories. Like all other absolute conceptions, it belongs to Reason, and must therefore await treatment in the Dialectic. These admissions come, however, only after the discussion has been completed. Had Kant reversed the order of the two paragraphs which constitute this digression, and marked them off as being a digression, he would have greatly assisted the reader in following the argument.