The Critique of Practical Reason [29]
one which is not determinable by physical laws, and consequently is not capable of any empirical intuition in proof of its reality, but, nevertheless, completely justifies its objective reality a priori in the pure practical law; not, indeed (as is easily seen) for the purposes of the theoretical, but of the practical use of reason. Now the notion of a being that has free will is the notion of a causa noumenon, and that this notion involves no contradiction, we are already assured by the fact- that inasmuch as the concept of cause has arisen wholly from pure understanding, and has its objective reality assured by the deduction, as it is moreover in its origin independent of any sensible conditions, it is, therefore, not restricted to phenomena (unless we wanted to make a definite theoretic use of it), but can be applied equally to things that are objects of the pure understanding. But, since this application cannot rest on any intuition (for intuition can only be sensible), therefore, causa noumenon, as regards the theoretic use of reason, although a possible and thinkable, is yet an empty notion. Now, I do not desire by means of this to understand theoretically the nature of a being, in so far as it has a pure will; it is enough for me to have thereby designated it as such, and hence to combine the notion of causality with that of freedom (and what is inseparable from it, the moral law, as its determining principle). Now, this right I certainly have by virtue of the pure, not-empirical origin of the notion of cause, since I do not consider myself entitled to make any use of it except in reference to the moral law which determines its reality, that is, only a practical use. If, with Hume, I had denied to the notion of causality all objective reality in its [theoretic] use, not merely with regard to things in themselves (the supersensible), but also with regard to the objects of the senses, it would have lost all significance, and being a theoretically impossible notion would have been declared to be quite useless; and since what is nothing cannot be made any use of, the practical use of a concept theoretically null would have been absurd. But, as it is, the concept of a causality free from empirical conditions, although empty, i.e., without any appropriate intuition), is yet theoretically possible, and refers to an indeterminate object; but in compensation significance is given to it in the moral law and consequently in a practical sense. I have, indeed, no intuition which should determine its objective theoretic reality, but not the less it has a real application, which is exhibited in concreto in intentions or maxims; that is, it has a practical reality which can be specified, and this is sufficient to justify it even with a view to noumena. Now, this objective reality of a pure concept of the understanding in the sphere of the supersensible, once brought in, gives an objective reality also to all the other categories, although only so far as they stand in necessary connexion with the determining principle of the will (the moral law); a reality only of practical application, which has not the least effect in enlarging our theoretical knowledge of these objects, or the discernment of their nature by pure reason. So we shall find also in the sequel that these categories refer only to beings as intelligences, and in them only to the relation of reason to the will; consequently, always only to the practical, and beyond this cannot pretend to any knowledge of these beings; and whatever other properties belonging to the theoretical representation of supersensible things may be brought into connexion with these categories, this is not to be reckoned as knowledge, but only as a right (in a practical point of view, however, it is a necessity) to admit and assume such beings, even in the case where we [conceive] supersensible beings (e.g., God) according to analogy, that is, a purely rational relation, of which we make a practical use with reference to what is sensible; and thus the application to the supersensible solely in