Note 1096 — Chapter II · DEDUCTION OF THE PURE CONCEPTS OF THE UNDERSTANDING (continued 4)

There is this difference between the category of existence and the categories of relation, namely, that it would seem to be impossible to distinguish between a determinate and an indeterminate application of it. Either we assert existence or we do not; there is no such third alternative as in the case of the categories of substance and causality. The category of substance, determinately used, signifies material existence in space and time; indeterminately applied it is the purely problematic and merely logical notion of something that is always a subject and never a predicate. The determinate category of causality is the conception of events conditioning one another in time; indeterminately employed it signifies only the quite indefinite notion of a ground or condition. Also, Kant’s explicit teaching (A 597 ff. = B 625 ff.) is that the notion of existence stands in an altogether different position from other predicates. It is not an attribute constitutive of the concept of the subject to which it is applied, but is simply the positing of the content of that concept as a whole. Nor, again, is it a relational form for the articulation of content. These would seem to be the reasons why no distinction is possible between a determinate and an indeterminate application of the notion of existence, and why, therefore, Kant, in defending the possible dual employment of it, has difficulty in holding consistently to the doctrines expounded in the Postulates. He is, by his own explicit teaching, interdicted from declaring that the notion of existence is both a category and not a category, or, in other words, that it may vary in meaning according as empirical or noumenal reality is referred to, and that only in the former case is it definite and precise. Yet such a view would, perhaps, better harmonise with certain other lines of thought which first obtain statement in the Dialectic. For though it is in the Dialectic that Kant expounds his grounds for holding that existence and content are separate and independent, it is there also that he first begins to realise the part which the Ideas of Reason are called upon to play in the drawing of the distinction between appearance and reality.