Kant adds a refutation of the merely logical arguments by which Leibniz had professed to establish the priority and greater scope of the possible. From the proposition, everything actual is possible, we can infer by immediate inference that some possible things are actual. That, however, would seem to imply that part of the possible is not actual, and that something must be added to the possible in order to constitute the actual. But this, Kant replies, is obviously an untenable view. The something additional to the possible, not being itself possible, we should be constrained to regard as impossible. For our understanding,[1279] the possible is that which connects with some perception in agreement with the formal conditions of experience. (Kant here gives the correct Critical definition of the possible, by combining the two first postulates.) Whether, and how far, other existences beyond the field of sense experience are possible, we have no means of deciding.
B 288-294.—This second edition section emphasises the fact that possibility cannot be determined through the categories alone, but only through the categories in their relation to intuition, and indeed to outer intuition. Possibility is throughout taken as referring to objective reality. The section is chiefly important in connection with the problems bearing on the relation of inner and outer sense and on the nature of our consciousness of time.[1280]
In B 289-91 Kant criticises those rationalistic arguments which rest upon the equating of necessity of thought with necessity of existence. When it is sought by mere analysis of concepts to prove that all accidental existence has a cause, the most that can be shown is that the existence of the accidental cannot be comprehended by us, unless the existence of a cause be assumed. But we may not argue that a condition of possible understanding is likewise a condition of possible existence.[1281] What is or is not possible for thought is, without special proof, no sufficient criterion of what is or is not possible in the real. If, again, the term accidental be taken as meaning that which can exist only as a consequence of some other existence, the general principle becomes merely analytic, and must not be taken as establishing the synthetic principle of causality. The latter demands transcendental proof by reference to the possibility of contingent experience.
CHAPTER III
ON THE GROUND OF THE DISTINCTION OF ALL OBJECTS WHATEVER INTO PHENOMENA AND NOUMENA
THIS chapter, as Kant himself states,[1282] can yield no new results. It will serve merely to summarise those already established in the Analytic, showing how they one and all converge upon a conclusion of supreme importance for understanding the nature and scope of human experience—the conclusion, that though the objective employment of the categories can be justified only within the realm of sense-experiences, they have a wider significance whereby they define a distinction between appearances and things in themselves. This is the conclusion which Kant now sets himself to illustrate and enforce in somewhat greater detail. It may be observed that the title of the chapter makes mention only of grounds for distinguishing between phenomena and noumena. That things in themselves really exist, Kant, as we shall find, never seriously thought of questioning.
Kant begins by recalling a main point in the preceding argument. The categories apart from the manifold of sensibility are merely logical functions without content.[1283] Though a priori, they require to be supplemented through empirical intuition.
“Apart from this relation to possible experience they have no objective validity of any sort, but are a mere play of the imagination or the understanding with their respective representations.”[1284]
As evidence of the truth of this conclusion Kant now adds a further argument, namely, the impossibility of defining the categories except in terms that involve reference to the conditions of sensibility.[1285] When these conditions are omitted, the categories are without relation to any object and consequently without meaning. They are no longer concepts of possible empirical employment, but only of “things in general.” When, for instance, the permanence of existence in time, which is the condition of the empirical application of the concept of substance, is omitted, the category reduces merely to the notion of something that is always a subject and never a predicate.
“But not only am I ignorant of all conditions under which this logical pre-eminence may belong to anything, I can neither put such a concept to any use nor draw the least inference from it. For under these conditions no object is determined for its employment, and consequently we do not at all know whether it signifies anything whatsoever.”[1286]
In abstraction from sense-data, the categories still remain as concepts or thoughts, logically possible; but that is not to be taken as signifying that they still continue to possess meaning, i.e. reference to an object.[1287] And in the absence of ascertainable meaning they cannot, of course, be defined.