Page:History of Modern Philosophy (Falckenberg).djvu/414

392 KANT. true that freedom is a mere Idea, whose object can never be given to me in an experience, and whose reality, conse- quently, cannot be objectively known and proved, but nevertheless, is required with satisfactory subjective necessity as the condition of the moral law and of the possibility of its fulfillment. I may not say it is certain, but, with safety, I am certain that I am free. Freedom is not a dogmatic proposition of theoretical reason, but a postulate of practical reason ; and the latter holds the primacy over the former to this extent, that it can require the former to show that certain transcendent Ideas of the suprasensible, which are most intimately connected with moral obligation, are compatible with the principles of the understanding. It was just in view of the practical inter- ests involved in the rational concepts God, freedom, immor- tality, that it was so important to establish, at least, their possibility (their conceivability without contradiction). That, therefore, which the Dialectic recognized as possible is in the Ethics shown to be real : Whoever seeks to fulfill his moral destiny — and this is the duty of every man — must not doubt concerning the conditions of its possible fulfillment, must, in spite of their incomprehensibility, believe in freedom and a suprasensible world. They are both postulates of practical reason, i. e., assumptions concerning that which is in behalf of that which ought to be. Naturally the interests of the understanding must not be infringed upon by those of the will. The principle of the complete causal determination of events retains its validity unimpeached for the sphere of the knowledge of the understanding, that is, for the realm of phenomena ; while, on the other hand, it remains permissible for us to postulate another kind of causality for the realm of things in themselves, although we can have no idea of its how, and to ascribe to ourselves a free intelligible character. While the Idea of freedom can be derived directly from the moral law as a postulate thereof, the proof of the reality of the two other Ideas is effected indirectly by means of the concept of the " highest good," in which reason con- ceives a union of perfect virtue and perfect happiness. The moral law requires absolute correspondence between the