“This [objective ground of all association of appearances] can nowhere be found, except in the principle of the unity of apperception in respect of all forms of knowledge which can belong to me. In accordance with this principle all appearances must so enter the mind, or be so apprehended, that they fit together to constitute the unity of apperception. This would be impossible without synthetic unity in their connection, and that unity is therefore also objectively necessary. The objective unity of all empirical consciousness in one consciousness, that of original apperception, is therefore the necessary condition of all (even of all _possible_) perception; and the affinity of all appearances, near or remote, is a necessary consequence of a synthesis in imagination which is grounded _a priori_ on rules.”[902] The fundamental characteristic of consciousness is the unified form in which alone it can exist; only when this unity is recognised as indispensably necessary, and therefore as invariably present whenever consciousness exists at all, can the inter-relations of the contents of consciousness be properly defined. If this main contention of the Critical teaching be accepted, Hume’s associationist standpoint is no longer tenable. Association cannot be taken to be an ultimate and inexplicable property of our mental states. Nor is it a property which can be regarded as belonging to presentations viewed as so many independent existences. It is conditioned by the unity of consciousness, and therefore rests upon the “transcendental” conditions which Critical analysis reveals. Since the unity of consciousness conditions association, it cannot be explained as the outcome and product of the mechanism of association. In restating the objective deduction in the second edition, Kant has omitted all reference to this doctrine of objective affinity. His reasons for this omission were probably twofold. In the first place, it has been expounded in terms of a transcendental psychology, which, as we shall find, is conjectural in character. And secondly, the phrase “objective affinity” is, as I have already pointed out, decidedly misleading. It seems to imply that Kant is postulating, without independent proof, that noumenal conditions must be such as to supply an orderly manifold of sense data. But though the doctrine of objective affinity is eliminated, its place is to some extent taken[903] by the proof that all apprehension is an act of judgment and therefore involves factors which cannot be reduced to, or explained in terms of, association.