The Critique of Practical Reason [73]
so as to make it the real conception of a substance, a character which practical reason furnishes by the postulate of a duration required for accordance with the moral law in the summum bonum, which is the whole end of practical reason. 2. It leads to that of which speculative reason contained nothing but antinomy, the solution of which it could only found on a notion Problematically conceivable indeed, but whose objective reality it could not prove or determine, namely, the cosmological idea of an intelligible world and the consciousness of our existence in it, by means of the postulate of freedom (the reality of which it lays down by virtue of the moral law), and with it likewise the law of an intelligible world, to which speculative reason could only point, but could not define its conception. 3. What speculative reason was able to think, but was obliged to leave undetermined as a mere transcendental ideal, viz., the theological conception of the first Being, to this it gives significance (in a practical view, that is, as a condition of the possibility of the object of a will determined by that law), namely, as the supreme principle of the summum bonum in an intelligible world, by means of moral legislation in it invested with sovereign power. Is our knowledge, however, actually extended in this way by pure practical reason, and is that immanent in practical reason which for the speculative was only transcendent? Certainly, but only in a practical point of view. For we do not thereby take knowledge of the nature of our souls, nor of the intelligible world, nor of the Supreme Being, with respect to what they are in themselves, but we have merely combined the conceptions of them in the practical concept of the summum bonum as the object of our will, and this altogether a priori, but only by means of the moral law, and merely in reference to it, in respect of the object which it commands. But how freedom is possible, and how we are to conceive this kind of causality theoretically and positively, is not thereby discovered; but only that there is such a causality is postulated by the moral law and in its behoof. It is the same with the remaining ideas, the possibility of which no human intelligence will ever fathom, but the truth of which, on the other hand, no sophistry will ever wrest from the conviction even of the commonest man.
VII. How is it possible to conceive an Extension of Pure Reason in a Practical point of view, without its Knowledge as Speculative being enlarged at the same time?
In order not to be too abstract, we will answer this question at once in its application to the present case. In order to extend a pure cognition practically, there must be an a priori purpose given, that is, an end as object (of the will), which independently of all theological principle is presented as practically necessary by an imperative which determines the will directly (a categorical imperative), and in this case that is the summum bonum. This, however, is not possible without presupposing three theoretical conceptions (for which, because they are mere conceptions of pure reason, no corresponding intuition can be found, nor consequently by the path of theory any objective reality); namely, freedom, immortality, and God. Thus by the practical law which commands the existence of the highest good possible in a world, the possibility of those objects of pure speculative reason is postulated, and the objective reality which the latter could not assure them. By this the theoretical knowledge of pure reason does indeed obtain an accession; but it consists only in this, that those concepts which otherwise it had to look upon as problematical (merely thinkable) concepts, are now shown assertorially to be such as actually have objects; because practical reason indispensably requires their existence for the possibility of its object, the summum bonum, which practically is absolutely necessary, and this justifies theoretical reason in assuming them. But this extension of theoretical reason
VII. How is it possible to conceive an Extension of Pure Reason in a Practical point of view, without its Knowledge as Speculative being enlarged at the same time?
In order not to be too abstract, we will answer this question at once in its application to the present case. In order to extend a pure cognition practically, there must be an a priori purpose given, that is, an end as object (of the will), which independently of all theological principle is presented as practically necessary by an imperative which determines the will directly (a categorical imperative), and in this case that is the summum bonum. This, however, is not possible without presupposing three theoretical conceptions (for which, because they are mere conceptions of pure reason, no corresponding intuition can be found, nor consequently by the path of theory any objective reality); namely, freedom, immortality, and God. Thus by the practical law which commands the existence of the highest good possible in a world, the possibility of those objects of pure speculative reason is postulated, and the objective reality which the latter could not assure them. By this the theoretical knowledge of pure reason does indeed obtain an accession; but it consists only in this, that those concepts which otherwise it had to look upon as problematical (merely thinkable) concepts, are now shown assertorially to be such as actually have objects; because practical reason indispensably requires their existence for the possibility of its object, the summum bonum, which practically is absolutely necessary, and this justifies theoretical reason in assuming them. But this extension of theoretical reason