The self-consciousness of the subjective deduction, in the preliminary form above stated, is, however, itself empirical. Kant, developing on more strictly Critical lines the argument which had accompanied his earlier doctrine of the transcendental object, now proceeds to maintain in what is at once the most fruitful and the most misleading of his tenets, that the ultimate ground of the possibility of consciousness and therefore also of empirical self-consciousness is the transcendental unity of apperception. Such apperception, to use Kant’s ambiguous phraseology, precedes experience as its _a priori_ condition. The interpretation of given appearances through _a priori_ categories is a necessity of consciousness because it is a condition of self-consciousness; and it is a condition of self-consciousness because it alone will account for the transcendental apperception upon which all empirical self-consciousness ultimately depends. One chief reason why Kant’s deduction is found so baffling and illusive is that it rests upon an interpretation of the unity of apperception which is very definitely drawn, but to which Kant himself gives only the briefest and most condensed expression. I shall therefore take the liberty of restating it in more explicit terms. The true or transcendental self has no content of its own through which it can gain knowledge of itself. It is mere identity, I am I. In other words, self-consciousness is a mere _form_ through which contents that never themselves constitute the self are yet apprehended as being objects to the self. Thus though the self in being conscious of time or duration must be conscious of itself as _identical_ throughout the succession of its experiences, that identity can never be discovered in those experiences; it can only be thought as a condition of them. The continuity of memory, for instance, is not a possible substitute for transcendental apperception. As the subjective deduction demonstrates, self-consciousness conditions memory, and cannot therefore be reduced to or be generated by it.[892] When, however, such considerations are allowed their due weight, the necessity of postulating a transcendental unity becomes only the more evident. Though it can never itself be found among appearances, it is an interpretation which we are none the less compelled to give to appearances.