“The synthetic proposition, that all the variety of empirical consciousness must be combined in a single self-consciousness, is the absolutely first and synthetic principle of our thought in general.”[897]

We may at this point consider Kant’s doctrine of “objective affinity.” It excellently enforces the main thesis which he is professing to establish, namely, that the conditions of unitary consciousness are the conditions of all consciousness. The language, however, in which the doctrine is expounded is extremely obscure and difficult; and before commenting upon Kant’s own methods of statement, it seems advisable to paraphrase the argument in a somewhat free manner, and also to defer consideration of the transcendental psychology which Kant has employed in its exposition.[898] Association can subsist only between ideas, both of which have occurred within the same conscious field. Now the fundamental characteristic of consciousness, the very condition of its existing at all, is its unity; and until this has been recognised, there can be no understanding of the associative connection which arises under the conditions which consciousness supplies. To attempt to explain the unity of consciousness through the mechanism of association is to explain an agency in terms of certain of its own effects. It is to explain the fundamental in terms of the derivative, the conditions in terms of what they have themselves made possible. Kant’s argument is therefore as follows. Ideas do not become associated merely by co-existing. They must occur together in a unitary consciousness; and among the conditions necessary to the possibility of association are therefore the conditions of the possibility of experience. Association is transcendentally grounded. So far from accounting for the unity of consciousness, it presupposes the latter as determining the conditions under which alone it can come into play.

“...how, I ask, is association itself possible?... On my principles the thorough-going affinity of appearances is easily explicable. All possible appearances belong as representations to the totality of a possible self-consciousness. But as this self-consciousness is a transcendental representation, numerical identity is inseparable from it and is a priori certain. For nothing can come to our knowledge save in terms of this original apperception. Now, since this identity must necessarily enter into the synthesis of all the manifold of appearances, so far as the synthesis is to yield empirical knowledge, the appearances are subject to a priori conditions, with which the synthesis of their apprehension must be in complete accordance.... Thus all appearances stand in a thorough-going connection according to necessary laws, and therefore in a transcendental affinity of which the empirical is a mere consequence.”[899]

In other words, representations must exist in consciousness before they can become associated; and they can exist in consciousness only if they are consciously apprehended. But in order to be consciously apprehended, they must conform to the transcendental conditions upon which all consciousness rests; and in being thus apprehended they are set in thoroughgoing unity to one another and to the self. They are apprehended as belonging to an objective order or unity which is the correlate of the unity of self-consciousness. This is what Kant entitles their objective affinity; it is what conditions and makes possible their associative or empirical connection.

This main point is very definitely stated in A 101.

“If we can show that even our purest a priori intuitions yield no knowledge, save in so far as they contain such a connection of the manifold as will make possible a thoroughgoing synthesis of reproduction, this synthesis of the imagination” [which acts through the machinery of association] “must be grounded, prior to all experience, on a priori principles, and since experience necessarily presupposes that appearances can be reproduced, we shall have to assume a pure transcendental synthesis of the imagination” [i.e. such synthesis as is involved in the unity of consciousness] “as conditioning even the possibility of all experience.”[900]

In A 121-2 Kant expresses his position in a more ambiguous manner. He may seem to the reader merely to be arguing that a certain minimum of regularity is necessary in order that representations may be associated, and experience may be possible.[901] But the general tenor of the passage as a whole, and especially its concluding sentences, enforce the stronger, more consistent, thesis.

”[The] subjective and empirical ground of reproduction according to rules is named the association of representations. If this unity of association did not also have an objective ground, which makes it impossible that appearances should be apprehended by the imagination except under the condition of a possible synthetic unity of this apprehension, it would be entirely accidental that appearances should fit into a connected whole of human knowledge. For even though we had the power of associating perceptions, it would remain entirely undetermined and accidental whether they would themselves be associable; and should they not be associable, there might exist a multitude of perceptions, and indeed an entire sensibility, in which much empirical consciousness would arise in my mind, but in a state of separation, and without belonging to one consciousness of myself. That, however, is impossible. For only in so far as I ascribe all perceptions to one consciousness (original apperception), can I say in all perceptions that I am conscious of them. There must therefore be an objective ground (that is, one that can be recognised a priori, antecedently to all empirical laws of the imagination) upon which may rest the possibility, nay the necessity, of a law that extends to all appearances....”

Kant is not merely asserting that the associableness of ideas, and the regularity of connection which that implies, must be postulated as a condition of experience. That would be a mere begging of the issue; the correctness of the postulate would not be independently proved. Kant is really maintaining the much more important thesis, that the unity of experience, i.e. of consciousness, is what makes association possible at all. And since consciousness must be unitary in order to exist, there cannot be any empirical consciousness in which the conditions of association, and therefore of reproduction, are not to be found.

A further misunderstanding is apt to be caused by Kant’s statement that associative affinity rests upon objective affinity. This seems to imply, in the same manner as the passage which we have just considered, that instead of proving that appearances are subject to law and order, he is merely postulating that an abiding ground of such regularity must exist in the noumenal conditions of the sense manifold. But he himself again supplies the needful correction.