Page 87 of 93

If we look merely to the way in which anything can be for us (according to the subjective constitution of our representative powers) an Object of knowledge (res cognoscibilis), then our concepts will not cohere with Objects, but merely with our cognitive faculties and the use which they can make of a given representation (in a theoretical or practical point of view). Thus the question whether anything is or is not a cognisable being is not a question concerning the possibility of things but of our knowledge of them.

Cognisable things are of three kinds: things of opinion (opinabile); things of fact (scibile); and things of faith (mere credibile).

(1.) Objects of mere rational Ideas, which for theoretical knowledge cannot be presented in any possible experience, are so far not cognisable things, and consequently in respect of them we can form no opinion; for to form an opinion a priori is absurd404 in itself and the straight road to mere chimeras. Either then our proposition is certain a priori or it contains nothing for belief. Therefore things of opinion are always Objects of an empirical cognition at least possible in itself (objects of the world of sense); but, which, on account merely of the [low] degree of this faculty that we possess, is for us impossible. Thus the ether of the new physicists,144 an elastic fluid pervading all other matter (mingled intimately with it) is a mere thing of opinion, yet is such that, if our external senses were sharpened to the highest degree, it could be perceived; though it can never be presented in any observation or experiment. To assume [the existence of] rational inhabitants of other planets is a thing of opinion; for if we could come closer to them, which is in itself possible, we should decide by experience whether they did or did not exist; but as we shall never come so near, it remains in the region of opinion. But to hold the opinion that there are in the material universe pure thinking spirits without bodies (viz. if we dismiss as unworthy of our notice certain phenomena which have been published as actual145) is to be called poetic fiction. This is no thing of opinion, but a mere Idea which remains405 over, when we remove from a thinking being everything material, and only leave thought to it. Whether then the latter (which we know only in man, that is, in combination with a body) does survive, we cannot decide. Such a thing is a sophistical being (ens rationis ratiocinantis), not a rational being (ens rationis ratiocinatae)146; of which latter it is possible to show conclusively, the objective reality of its concept; at least for the practical use of Reason, because this which has its peculiar and apodictically certain principles a priori, demands (postulates) it.

(2.) Objects for concepts, whose objective reality can be proved (whether through pure Reason or through experience, and, in the first case, from its theoretical or practical data, in all cases by means of a corresponding intuition) are things of fact (res facti).147 Of this kind are the mathematical properties of magnitudes (in geometry), because they are susceptible of a presentation a priori for the theoretical use of Reason. Further, things or their characteristics, which can be exhibited in experience (either our own or that of others through the medium of testimony) are likewise things of fact.—And, what is very remarkable, there is one rational Idea (susceptible in itself of no presentation406 in intuition, and consequently, of no theoretical proof of its possibility) which also comes under things of fact. This is the Idea of freedom, whose reality, regarded as that of a particular kind of causality (of which the concept, theoretically considered, would be transcendent), may be exhibited by means of practical laws of pure Reason, and conformably to this, in actual actions, and, consequently, in experience.—This is the only one of all the Ideas of pure Reason, whose object is a thing of fact, and to be reckoned under the scibilia.

(3.) Objects, which in reference to the use of pure practical Reason that is in conformity with duty must be thought a priori (whether as consequences or as grounds), but which are transcendent for its theoretical use, are mere things of faith. Of this kind is the highest good in the world, to be brought about by freedom.148 The concept of this cannot be established as regards its objective reality in any experience possible for us and thus adequately for the theoretical use of Reason; but its use is commanded by practical pure Reason [in reference to the best possible working out of that purpose],149 and it consequently must be assumed possible. This commanded effect, together with the only conditions of its possibility thinkable by us, viz. the Being of God and the immortality of the soul, are things of faith (res fidei), and of all objects are the only ones which can be so called.150 For though what we learn407 by testimony from the experience of others must be believed by us, yet it is not therefore a thing of faith; for it was the proper experience of some one witness and so a thing of fact, or is presupposed as such. Again it must be possible by this path (that of historical faith) to arrive at knowledge; and the Objects of history and geography, like everything in general which it is at least possible to know by the constitution of our cognitive faculties, belong not to things of faith but to things of fact. It is only objects of pure Reason which can be things of faith at all, though not as objects of the mere pure speculative Reason: for then they could not be reckoned with certainty among things, i.e. Objects of that cognition which is possible for us. They are Ideas, i.e. concepts of the objective reality of which we cannot theoretically be certain. On the other hand, the highest final purpose to be worked out by us, by which alone we can become worthy of being ourselves the final purpose of creation, is an Idea which has in a practical reference objective reality for us, and is also a thing. But because we cannot furnish such reality to this concept in a theoretical point of view, it is a mere thing of faith of the pure Reason, along with God and Immortality, as the conditions under which alone we, in accordance with the constitution of our (human) Reason, can conceive the possibility of that effect of the use of our freedom in conformity with law. But belief in things of faith is a belief in a pure practical point of view, i.e. a moral faith, which proves nothing for theoretical pure rational cognition, but only for that which is practical and directed to the fulfilment of its duties; it in no way extends speculation or the practical rules of prudence in accordance with the principle of self-408love. If the supreme principle of all moral laws is a postulate, so is also the possibility of its highest Object; and consequently, too, the condition under which we can think this possibility is postulated along with it and by it. Thus the cognition of the latter is neither knowledge nor opinion of the being and character of these conditions, regarded as theoretical cognition; but is a mere assumption in a reference which is practical and commanded for the moral use of our Reason.