only concept of this kind to be met with in human Reason is that of the freedom of men under moral laws, along with the final purpose which Reason prescribes by these laws. Of these two [the moral laws and the final purpose] the first are useful for ascribing to the Author of Nature, the second for ascribing to man, those properties which contain the necessary condition of the possibility of both [God and the soul]; so that from this Idea a conclusion can be drawn as to the existence and constitution of these beings which are otherwise quite hidden from us. Thus the ground of the failure of the attempt to prove God and immortality by the merely theoretical path lies in this, that no cognition whatever is possible of the supersensible in this way (of natural concepts). The ground of its success by the moral way (of the concept of freedom) is as follows. Here the supersensible (freedom), which in this case is fundamental, by a determinate law of causality that springs from it, not only supplies material for cognition of other supersensibles (the moral final purpose and the conditions of its attainability), but also establishes its reality in actions as a fact; though at the same time it can furnish a valid ground of proof in no other than a practical point of view (the only one, however, of which Religion has need). It is thus very remarkable that of the three pure rational Ideas, _God_, _freedom_, and _immortality_, that of freedom is the only concept of the supersensible which (by means of the causality that is thought in it) proves its objective reality in nature by means of the effects it can produce there; and thus renders possible the connexion of both the others with nature, and of all three together with Religion. We have therefore in us a principle capable of determining the Idea of the supersensible within us, and thus also that of the supersensible without us, for knowledge, although only in a practical point of view; a principle this of which mere speculative philosophy (which could give a merely negative concept of freedom) must despair. Consequently the concept of freedom (as fundamental concept of all unconditioned practical laws) can extend Reason beyond those bounds, within which every natural (theoretical) concept must remain hopelessly limited. _General remark on Teleology_ If the question is, what rank the moral argument, which proves the Being of God only as a thing of faith for the practical pure Reason, maintains among the other arguments in philosophy, it is easy to set aside the whole achievement of this last; by which it appears that there is no choice, but that our theoretical faculty must give up all its pretensions before an impartial criticism.