As noted above,[688] the asserted parallelism of analytic and synthetic judgment rests upon the further assumption that discursive thinking and synthetic interpretation are the outcome of one and the same faculty of understanding. It is implied, in accordance with the attitude of the pre-Critical _Dissertation_, that understanding, viewed as the faculty to which all thought processes are due, has certain laws in accordance with which it necessarily acts in all its operations, and that these must therefore be discoverable from analytic no less than from synthetic thinking. The mingling of truth and falsity in this assumption has already been indicated. Such truth as it contains is due to the fact that analytic thinking is not co-ordinate with, but is dependent upon, and determined by, the forms of synthetic thinking. Its falsity consists in its ignoring of what thus gives it partial truth. The results of the transcendental deduction call for a complete recasting of the entire argument of the metaphysical deduction. And when this is done, there is no longer any ground for the contention that the number of the categories is determinable on _a priori_ grounds. On Kant’s own fundamental doctrine of the synthetic, and therefore merely _de facto_, character of all _a priori_ principles, the necessity of the categories is only demonstrable by reference to the contingent fact of actual experience. The possible conceptual forms are relative to actual and ultimate differences in the contingent sensuous material; and being thus relative, they cannot possibly be systematised on purely _a priori_ grounds. This Kant has himself admitted in a passage added in the second edition,[689] though apparently without full consciousness of the important consequences which must follow. “This peculiarity of our understanding that it can produce _a priori_ unity of apperception solely by means of the categories, and only by such and so many, is as little capable of further explanation as why we have just these and no other functions of judgment, or why space and time are the only forms of our possible intuition.” STAGES IN THE DEVELOPMENT OF KANT’S METAPHYSICAL DEDUCTION The character of the metaphysical deduction will be placed in a clearer light if we briefly trace the stages, so far as they can be reconstructed, through which it passed in Kant’s mind. We may start from the _Dissertation_ of 1770. Kant there modifies his earlier Wolffian standpoint, developing it, probably under the direct influence of the recently published _Nouveaux Essais_, on more genuinely Leibnizian lines.