(2)[954] Besides the manifold and its synthesis a further factor is involved in the conception of combination, namely, the representation of the unity of the manifold. The combination which is necessary to and constitutes knowledge is representation of the synthetical unity of the manifold. This is a factor additional to synthesis and to the manifold synthesised. For such representation cannot arise out of any antecedent consciousness of synthesis. On the contrary, it is only through supervention upon the unitary synthesis that the conception of the combination becomes possible. In other words, the representation of unity conditions consciousness of synthesis, and therefore cannot be the outcome or product of it. This is an application, or rather generalisation, of a position which in the first edition is developed only in reference to the empirical process of recognition. Recognition preconditions consciousness, and therefore cannot be subsequent upon it.

(3)[955] The unity thus represented is not, however, that which is expressed through the category of unity. The consciousness of unity which is involved in the conception of synthesis is that of apperception or transcendental self-consciousness. This is the highest and most universal form of unity, for it is a presupposition of the unity of all possible concepts, whether analytic or synthetic, in the various forms of judgment.

(4)[956] A manifold though given is not for that reason also represented. It must be possible for the ‘I think’ to accompany it and all my other representations:

“...for otherwise something would be represented in me which could not be thought at all; and that is equivalent to saying that the representation would be impossible or at least would be nothing to me.”[957]

But to ascribe a manifold as my representations to the identical self is to comprehend them, as synthetically connected, in one apperception.[958] Only what can be combined in one consciousness can be related to the ‘I think.’ The analytic unity of self-consciousness presupposes the synthetic unity of the manifold.

(5)[959] The unity of apperception is analytic or self-identical. It expresses itself through the proposition, I am I. But being thus pure identity without content of its own, it cannot be conscious of itself in and by itself. Its unity and constancy can have meaning only through contrast to the variety and changeableness of its specific experiences; and yet, at the same time, it is also true that such manifoldness will destroy all possibility of unity unless it be reconcileable with it. The variety can contribute to the conditioning of apperception only in so far as it is capable of being combined into a single consciousness. Through synthetic unifying of the manifold the self comes to consciousness both of itself and of the manifold.

(6)[960] The transcendental original unity of apperception is an objective, not a merely subjective, unity. Its conditions are also the conditions in and through which we acquire consciousness of objects. An object is that in the conception of which the manifold of given intuitions is combined. (This point, though central to the argument, is more adequately developed in the first than in the second edition.) Such combination requires unity of consciousness. Thus the same unity which conditions apperception likewise conditions the relation of representations to an object. The unity of pure apperception may therefore be described as an objective unity for two reasons: first, because it can apprehend its own analytical unity only through discovery of unity in the given, and secondly, for the reason that such synthetical unifying of the manifold is also the process whereby representations acquire reference to objects.

(7)[961] Kant reinforces this conclusion, and shows its further significance, by analysis of the act of judgment. The logical definition of judgment, as the representation of a relation between two concepts, has many defects. These, however, are all traceable to its initial failure to explain, or even to recognise, the nature of the assertion which judgment as such claims to make. Judgment asserts relations of a quite unique kind, altogether different from those which exist between ideas connected through association. If, for instance, on seeing a body the sensations of weight due to the attempt to raise it are suggested by association, there is nothing but subjective sequence; but if we form the judgment that the body is heavy, the two representations are then connected together in the object. This is what is intended by the copula ‘is.’ It is a relational term through which the objective unity of given representations is distinguished from the subjective. It indicates that the representations stand in objective relation under the pure unity of apperception, and not merely in subjective relation owing to the play of association in the individual mind. “Judgment is nothing but the mode of bringing cognitions to the objective unity of apperception,” i.e. of giving to them a validity which holds independently of the subjective processes through which it is apprehended. Objective relations are not, of course, all necessary or universal; and a judgment may, therefore, assert a relation which is empirical and contingent. None the less the fundamental distinction between it and any mere relation of association still persists. The empirical relation is still in the judgment asserted to be objective. The subject and the predicate are asserted, in the particular case or cases to which the judgment refers, to be connected in the object and not merely in the mind of the subject. Or otherwise stated, though subject and predicate are not themselves declared to be necessarily and universally related to one another, their contingent relation has to be viewed as objectively, and therefore necessarily, grounded. Judgment always presupposes the existence of necessary relations even when it is not concerned to assert them. Judgment is the organ of objective knowledge, and is therefore bound up, indirectly when not directly, with the universality and necessity which are the sole criteria of knowledge. The judgment expressive of contingency is still judgment, and is therefore no less necessary in its conditions, and no less objective in its validity, than is a universal judgment of the scientific type. To use Kant’s own terminology, judgment acquires objective validity through participation in the necessary unity of apperception. In so doing it is made to embody those principles of the objective determination of all representations through which alone cognition is possible.

(8)[962] As judgment is nothing but the mode of bringing cognitions to the objective unity of apperception, it follows that the categories, which in the metaphysical deduction have been proved to be the possible functions in judging, are the conditions in and through which such pure apperception becomes possible. Apperception conditions experience, and the unity which both demand for their possibility is that of the categories.

Before passing to the remaining sections of the deduction,[963] which are supplementary rather than essential, I may add comment upon the above points. Only (7) and (8) call for special consideration. They represent a form of argument which has no counterpart in the first edition. As we noted,[964] the first edition argument is defective owing to its failure to demonstrate that the categories constitute the unity which is necessary to knowledge. By introducing in the second edition this analysis of judgment, and by showing the inseparable connection between pure apperception, objective consciousness and judgment, this defect is in some degree removed. As the categories correspond to the possible functions of judgment, their objective validity is thereby established. By this means also the connection which in Kant’s view exists between the metaphysical and the transcendental deductions receives for the first time proper recognition. The categories which in the former deduction are discovered and systematised through logical analysis of the form of judgment, are in the latter deduction, through transcendental analysis of the function of judgment, shown to be just those forms of relation which are necessary to the possibility of knowledge. It must, however, be noted that the transcendental argument is brought to completion only through assumption of the adequacy of the metaphysical deduction. No independent attempt is made to show that the particular categories obtained in the metaphysical deduction are those which are required, that there are no others, or that all the twelve are indispensable.