Kant, be it observed, ridiculed all empirical stimuli of the will, and began by removing everything, whether subjective or objective, on which a law determining the will's action could be empirically based. The consequence is, that he has nothing left for the substance of his law but simply its =Form=. Now this can only be the abstract conception of =lawfulness=. But the conception of lawfulness is built up out of what is valid for all persons equally. Therefore the substance of the law consists of the conception of what is universally valid, and its contents are of course nothing else than its =universal validity=. Hence the formula will read as follows: "Act only in accordance with that precept which you can also wish should be a general law for all rational beings." This, then, is the real foundation--for the most part so greatly misunderstood--which Kant constructed for his principle of Morals, and therefore for his whole ethical system. Compare also the _Kritik der Praktischen Vernunft_, p. 61 (R., p. 147); the end of Note 1. I pay Kant a tribute of sincere admiration for the great acumen he displayed in carrying out this dexterous feat, but I continue in all seriousness my examination of his position according to the standard of truth. I will only observe--and this point I shall take up again later on--that here =reason=, because, and in so far as, it works out the above explained special ratiocination, receives the name of =practical reason=. Now the Categorical Imperative of Practical Reason is the law which results from this process of thought. Consequently Practical Reason is not in the least what most people, including even Fichte, have regarded it--a special faculty that cannot be traced to its source, a _qualitas occulta_, a sort of moral instinct, like Hutcheson's "moral sense"; but it is (as Kant himself in his preface, p. xii. [R., p. 8], and elsewhere, often enough declares) one and the same with =theoretical reason=--is, in fact, =theoretical reason= itself, in so far as the latter works out the ratiocinative process I have described. It is noticeable that Fichte calls the Categorical Imperative of Kant an =absolute Postulate= (_Grundlage der gesammten Wissenschaftslehre_, Tübingen, 1802, p. 240, Note). This is the modern, more showy, expression for _petitio principii_, and thus we see that he, too, regularly accepted the Categorical Imperative, and consequently must be included among those who have fallen into the mistake above criticised.