However, in place of a deducti of the supreme principle of pure practical reason,.e., explanation of the possibility of such an a priori cognition, we were able to adduce nothing more than this: that if one had insight into the possibility of the freedom of an efficient cause, then one would also have insight not merely into the possibility but even into the necessity of the moral law as the supreme practical law of rational beings, to whom one attributes freedom of the causality of their will.