Vaihinger places III. δ next in order, on account of the connection of its argument with III. α.[822] But it dwells only upon the chief outcome of the total argument, viz. that the orderliness of nature is due to understanding. That productive imagination is not mentioned, is taken by Vaihinger to signify Kant’s recognition that it can be postulated only hypothetically, and that as doctrine it is not absolutely essential to the strict deduction. S summarises the entire argument, and in it “pure imagination” receives mention. Within this third stage III. γ is subsequent to the above four sections. For it carries the doctrine of productive imagination one step further. In III. β, III. α, and S, productive imagination has been treated merely as an auxiliary function of pure understanding. “The unity of apperception in relation to the synthesis of imagination is the _understanding_; and the same unity with reference to the transcendental synthesis of the imagination is the _pure understanding_.”[823] It is now treated as a separate and distinct faculty. So far from being a function of understanding, its synthesis “by itself, though carried out _a priori_, is always sensuous.”[824] It is “one of the fundamental faculties of the human soul.... The two extreme ends, sensibility and understanding, must be brought into connection with each other by means of this transcendental function of imagination.”[825] In this section there also appears a new element which would seem to connect it with the next following stage, namely, the addition to the series, apprehension, association, and reproduction, of the further process, recognition. As here introduced it is extremely ambiguous in character. It is counted as being empirical, and yet as containing _a priori_ concepts. This decidedly hybrid process would seem to represent Kant’s first formulation of the even more ambiguous process, which corresponds to it in the fourth stage. In III. I recognition is again mentioned, but this time in a form still more akin to its treatment in the fourth stage. It is not recognition through categories, but, as a form in apperception, is the “empirical consciousness of the identity of the reproductive representations with the appearances by which they were given.”[826] In all other respects, however, the above six sections agree (along with I. § 14 C) in holding to a threefold division of mental powers: sensibility, imagination, and apperception. This third stage is thereby marked off sufficiently clearly from the second stage in which pure imagination is wanting, and from the fourth stage in which it is dissolved into a threefold _a priori_ synthesis. In both I. § 14 C and in III. I the classification which underlies the third stage is explicitly formulated. Their statements harmoniously combine to yield the following tabular statement: