Third Section: Final Step from a Metaphysics of Morals to a Critique of Pure Practical Reason
The Concept of Freedom is the Key for an Explanation
of the Autonomy of the Will [446]
The will is a kind of causality belonging to living beings insofar as they are rational; freedom would be the property of this causality that makes it effective independent of any determination by alien causes. Similarly, natural necessity is the property of the causality of all non-rational beings by which they are determined to activity through the influence of alien causes.
The foregoing explanation of freedom is negative and is therefore unfruitful for attaining an insight regarding its essence; but there arises from it a positive concept, which as such is richer and more fruitful. The concept of causality Involves that of laws according to which something that we call cause must entail something else-namely, the effect. Therefore freedom is certainly not lawless, even though it is not a property of will in accordance with laws of nature. It must, rather, be a causality in accordance with Immutable laws, which, to be sure, is of a special kind; otherwise a free will would be something absurd. As we have already seen in the preceding paragraph), natural necessity is a heteronomy of efficient causes, Inasmuch as every effect is possible only in accordance with the law that something [447] else determines the efficient cause to exercise its causality. What else, then, can freedom of the will be but autonomy, i.e., the property that the will has of being a law to itself? The proposition that the will is in every action a law to itself expresses, however, nothing but the principle of acting according to no other maxim than that which can at the same time have itself as a universal law for its object. Now this is precisely the formula of the categorical imperative and is the principle of morality. Thus a free will and a will subject to moral laws are one and the same.
Therefore if freedom of the will is presupposed, morality (together with its principle) follows by merely analyzing the concept of freedom. However, the principle of morality is, nevertheless, a synthetic proposition: viz., an absolutely good will is one whose maxim can always have itself as content when such maxim is regarded as a universal law, it is synthetic because this property of the will’s maxim can never be found by analyzing the concept of an absolutely good will. Now such synthetic propositions are possible only as follows-two cognitions are bound together through their connection with a third in which both of them are to be found. The positive concept of freedom fumishes this third cognition, which cannot, as is the case with physical causes, be the nature of the world of sense (in whose concept is combined the concept of something as cause in relation to something else as effect). We cannot here yet show straight away what this third cognition is which freedom indicates to us and of which we have an a priori idea, nor can we as yet conceive of the deduction of the concept of freedom from pure practical reason and therewith also the possibility of a categorical Imperative. Rather, we require some further preparation.
Freedom Must Be Presupposed as a Property of the Will of All Rational Beings
It is not enough to ascribe freedom to our will, on whatever ground, if we have not also sufficient reason for attributing it to all rational beings. For inasmuch as morality serves as a law for us only Insofar as we are rational beings, it must also be valid for all rational beings. And since morality must be derived solely from the property of freedom, one must show that freedom is also the property of the will of all rational beings. It [448] is not enough to prove freedom from certain alleged experiences of human nature (such a proof is indeed absolutely impossible, and so freedom can be proved only a priori). Rather, one must show that freedom belongs universally to the activity of rational beings endowed with a will. Now I say that every being which cannot act in any way other than under the idea of freedom is for this very reason free from a practical point of view. This is to say that for such a being all the laws that are inseparably bound up with freedom are valid just as much as if the will of such a being could be declared to be free in itself for reasons that are valid for theoretical philosophy. Now I claim that we must necessarily attribute to every rational being who has a will also the idea of freedom, under which only can such a being act. For in such a being we think of a reason that is practical, Le., that has causality in reference to its objects. Now we cannot possibly think of a reason that consciously lets itself be directed from outside as regards its judgments; for in that case the subject would ascribe the determination of his faculty of judgment not to his reason, but to an impulse. Reason must regard itself as the author of its principles independent of foreign Influences. Therefore as practical reason or as the will of a rational being must reason regard itself as free. This is to say that the will of a rational being can be a will of its own only under the idea of freedom, and that such a will must there- fore, from a practical point of view, be attributed to all rational beings.
Concerning the Interest Attached to the Ideas of Morality
We have finally traced the determinate concept of morality back to the idea of freedom, but we could not prove freedom to be something actual in ourselves and in human nature. We saw merely that we must presuppose [449] it if we want to think of a being as rational and as endowed with consciousness of its causality as regards actions, i.e., as endowed with a will. And so we find that on the very same ground we must attribute to every being endowed with reason and a will this property of determining itself to action under the idea of its own freedom.
Now there resulted from the presupposition of this idea of freedom also the consciousness of a law of action: that the subjective principles of actions, i.e., maxims, must always be so adopted that they can also be valid objectively, i.e.. universally, as principles, and can therefore serve as universal laws of our own legislation. But why, then, should I subject myself to this principle simply as a rational being and by so doing also subject to this principle all other beings endowed with reason? I am willing to grant that no interest impels me to do so, because this would not give a categorical imperative. But nonetheless I must necessarily take an interest in it and discern how this comes about, for this ought is properly a would which is valid for every rational being, provided that reason is practical for such a being without hindrances. In the case of beings who, like ourselves, are also affected by sensibility, i.e., by incentives of a kind other than the purely rational, and who do not always act as reason by itself would act, this necessity of action is expressed only as an ought, and the subjective necessity is to be distinguished from the objective.
It therefore seems as if we have in the idea of freedom actually only presupposed the moral law, namely, the principle of the autonomy of the will, and as if we could not prove its reality and objective necessity Independently. In that case we should indeed still have gained something quite considerable by at least determining the genuine principle more exactly than had previously been done. But as regards its validity and the practical necessity of subjecting oneself to it, we would have made no progress. We could give no satisfactory answer if asked the following questions: why must the universal validity of our maxim taken as a law be a condition restricting our actions; upon what do we base the worth that we assign to this way of acting-a worth that is supposed to be so great that there can be no higher interest; how does it happen that by this alone does man believe that he feels his own personal worth, In comparison [450] with which that of an agreeable or disagreeable condition is to be regarded as nothing.
Indeed we do sometimes find that we can take an interest in a personal characteristic which involves no interest in any [external] condition but only makes us capable of participating in the condition in case reason were to effect the allotment. This is to say that the mere worthiness of being happy can of itself be of interest even without the motive of participating in this happiness. This judgment, however, is in fact only the result of the importance that we have already presupposed as belonging to moral laws (when by the idea of freedom we divorce ourselves from all empirical interest). However, in this way we are not as yet able to have any insight into why it is that we should divorce ourselves from such Interest, i.e., that we should consider ourselves as free in action and yet hold ourselves as subject to certain laws so as to find solely in our own person a worth that can compensate us for the loss of everything that gives worth to our condition. We do not see how this is possible and hence how the moral law can obligate us.
One must frankly admit that there is here a sort of circle from which, so it seems, there is no way to escape. In the order of efficient causes we assume that we are free so that we may think of ourselves as subject to moral laws in the order of ends. And we then think of ourselves as subject to these laws because we have attributed to ourselves freedom of the will. Freedom and self-legislation of the will are both autonomy and are hence reciprocal concepts. Since they are reciprocal, one of them cannot be used to explain the other or to supply its ground, but can at most be used only for logical purposes to bring seemingly different conceptions of the same object under a single concept (just as different fractions of the same value are reduced to lowest terms).
However, one recourse still remains open to us, namely, to inquire whether we do not take one point of view when by means of freedom we think of ourselves as a priori efficient causes, and another point of view when we represent ourselves with reference to our actions as effects which we see before our eyes.
No subtle reflection is required for the following observation, which even the commonest understanding may be supposed to make, though it does so in its own fashion through some obscure discrimination of the [451] faculty of judgment which it calls feeling: all representations that come to us without our choice (such as those of the senses) enable us to know objects only as they affect us; what they may be in themselves remains unknown to us. Therefore, even with the closest attention and the greatest clarity that the understanding can bring to such representations, we can attain to a mere knowledge of appearances but never to knowledge of things in themselves. Once this distinction is made (perhaps merely as a result of observing the difference between representations which are given to us from without and in which we are passive from those which we produce entirely from ourselves and in which we show our own activity), then there follows of itself that we must admit and assume that behind the appearances there is something else which is not appearance, namely, things in themselves. Inasmuch as we can never cognize them except as they affect us through our senses), we must admit that we can never come any nearer to them nor ever know what they are in themselves. This must provide a distinction, however crude, between a world of sense and a world of understanding; the former can vary considerably according to the difference of sensibility [and sense impressions] in various observers, while the latter, which is the basis of the former, remains always the same. Even with regard to himself, a man cannot presume to know what he is in himself by means of the acquaintance which he has through internal sensation. For since he does not, as it were, create himself and since he acquires the concept of himself not a prior but empirically, it is natural that he can attain knowledge even about himself only through Inner sense and therefore only through the appearance of his nature and the way in which his consciousness is affected. But yet he must necessarily assume that beyond his own subject’s constitution as composed of nothing but appearances there must be something else as basis, namely, his ego as constituted in itself. Therefore with regard to mere perception and the receptivity of sensations, he must count himself as belonging to the world of sense; but with regard to whatever there may be in him of pure activity (whatever reaches consciousness immediately and not through affecting the senses) he must count himself as belonging to the intellectual world, of which he has, however, no further knowledge.
Such a conclusion must be reached by a reflective man regarding all the things that may be presented to him. It is presumably to be found even in [452] the most ordinary understanding, which, as is well known, is quite prone to expect that behind objects of the senses there is something else Invisible and acting of itself. But such understanding spoils all this by making the invisible again sensible, i.e., it wants to make the Invisible an object of intuition; and thereby does it become not a bit wiser.
Now man really finds in himself a faculty which distinguishes him from all other things and even from himself Insofar as he is affected by objects. That faculty is reason, which as pure spontaneity is elevated even above understanding. For although the latter is also spontaneous and does not, like sense, merely contain representations that arise only when one is affected by things (and is therefore passive), yet understanding can produce by its activity no other concepts than those which merely serve to bring sensuous representations [Intuitions] under rules and thereby to unite them in one consciousness. Without this use of sensibility, understanding would think nothing at all. Reason, on the other hand, shows such a pure spontaneity in the case of what are called Ideas that it goes far beyond anything that sensibility can offer and shows its highest occupation in distinguishing the world of sense from the world of understanding, thereby prescribing limits to the understanding itself.
Therefore a rational being must regard himself qua intelligence (and hence not from the side of his lower powers) as belonging not to the world of sense but to the world of understanding. Therefore he has two standpoints from which he can regard himself and know laws of the use of his powers and hence of all his actions: first, insofar as he belongs to the world of sense subject to laws of nature (heteronomy); secondly, Insofar as he belongs to the intelligible world subject to laws which, independent of nature, are not empirical but are founded only on reason.
As a rational being and hence as belonging to the intelligible world, can man never think of the causality of his own will except under the idea of freedom; for Independence from the determining causes of the world of sense (an Independence which reason must always attribute to itself) is freedom. Now the idea of freedom is inseparably connected with the concept of autonomy, and this in turn with the universal principle of morality,[453] which ideally is the ground of all actions of rational beings, just as natural law is the ground of all appearances.
The suspicion that we raised earlier is now removed, viz., that there might be a hidden circle involved in our Inference from freedom to autonomy, and from this to the moral law-this is to say that we had perhaps laid down the Idea of freedom only for the sake of the moral law in order subsequently to infer this law in its turn from freedom, and that we had therefore not been able to assign any ground at all for this law but had only assumed it by begging a principle which well-disposed souls would gladly concede us but which we could never put forward as a demonstrable proposition. But now we see that when we think of ourselves as free, we transfer ourselves into the intelligible world as members and know the autonomy of the will together with its consequence, morality; whereas when we think of ourselves as obligated, we consider ourselves as belonging to the world of sense and yet at the same time to the intelligible world.
How Is a Categorical Imperative Possible?
The rational being counts himself, qua intelligence, as belonging to the intelligible world, and only insofar as he is an efficient cause belonging to the intelligible world does he call his causality a will. But on the other side, he is conscious of himself as being also a part of the world of sense, where his actions are found as mere appearances of that causality. The possibility of these actions cannot, however, be discerned through such causality, which we do not know; rather, these actions as belonging to the world of sense must be viewed as determined by other appearances, namely, desires and Inclinations. Therefore, if I were solely a member of the intelligible world, then all my actions would perfectly conform to the principle of the autonomy of a pure will; if I were solely a part of the world of sense, my actions would have to be taken as in complete conformity with the natural law of desires and inclinations, i.e., with the heteronomy of nature. (My actions would in the first case rest on the supreme principle of morality, In the second case on that of happiness.) But the intelligible world contains the ground of the world of sense and therefore also the ground of its laws; consequently, the Intelligible world is (and must be thought of as) directly legislative for my will (which belongs wholly to the intelligible world). Therefore, even though on the one hand I must regard myself as a being belonging to the world of sense, yet on the other hand shall I have to know myself as an intelligence and as [454] subject to the law of the intelligible world, i.e., to reason, which contains this law in the idea of freedom, and hence to know myself as subject to the autonomy of the will. Consequently, I must regard the laws of the intelligible world as imperatives for me, and the actions conforming to this principle as duties.
And thus are categorical imperatives possible because the idea of freedom makes me a member of an intelligible world. Now if I were a member of only that world, all my actions would always accord with autonomy of the will. But since I Intuit myself at the same time as a member of the world of sense, my actions ought so to accord. This categorical ought presents a synthetic a priori proposition, whereby in addition to my will as affected by sensuous desires there is added further the idea of the same will, but as belonging to the intelligible world, pure and practical of itself, and as containing the supreme condition of the former will insofar as reason is concerned. All this is similar to the way in which concepts [categories] of the understanding, which of themselves signify nothing but the form of law in general, are added to intuitions of the world of sense and thus make possible synthetic a priori propositions, upon which all knowledge of nature rests.
The practical use of ordinary human reason bears out the correctness of this deduction. There is no one, not even the meanest villain, provided only that he is otherwise accustomed to the use of reason, who, when presented with examples of honesty of purpose, of steadfastness in following good maxims, and of sympathy and general benevolence (even when involved with great sacrifices of advantages and comfort) does not wish that he might also possess these qualities. Yet he cannot attain these in himself only because of his inclinations and impulses; but at the same time he wishes to be free from such inclinations which are a burden to him. He thereby proves that by having a will free of sensuous Impulses he transfers himself in thought into an order of things entirely different from that of his desires in the field of sensibility. Since he cannot expect to obtain by the aforementioned wish any gratification of his desires or any condition that would satisfy any of his actual or even conceivable inclinations (Inasmuch as through such an expectation the very idea that elicited the wish would be deprived of its preeminence) he can only expect a greater intrinsic worth of his own person. This better person he believes himself to be when he transfers himself to the standpoint of a [455] member of the intelligible world, to which he is involuntarily forced by the idea of freedom, i.e., of being independent of determination by causes of the world of sense. From this standpoint he is conscious of having a good will, which by his own admission constitutes the law for the bad will belonging to him as a member of the world of sense-a law whose authority he acknowledges even while he transgresses it. The moral ought is, therefore, a necessary would insofar as he is a member of the intelligible world, and is thought by him as an ought only insofar as he regards himself as being at the same time a member of the world of sense.
All men think of themselves as free as far as their will is concerned. Hence arise all judgments upon actions as being such as ought to have been done, even though they were not done. But this freedom is not a concept of experience, nor can it be such, since it always holds, even though experience shows the opposite of those requirements represented as necessary under the presupposition of freedom. On the other hand, it is just as necessary that whatever happens should be determined without any exception according to laws of nature; and this necessity of nature is likewise no concept of experience, just because it involves the concept of necessity and thus of a prior knowledge. But this concept of nature is confirmed by experience and must inevitably be presupposed if there is to be possible experience, which is coherent knowledge of the objects of sense in accordance with universal laws. Freedom is, therefore, only an idea of reason whose objective reality is in itself questionable; but nature is a concept of the understanding, which proves, and necessarily must prove, its reality by examples from experience.
There arises from this a dialectic of reason, since the freedom attributed to the will seems to contradict the necessity of nature. And even though at this parting of the ways reason for speculative purposes finds the road of natural necessity much better worn and more serviceable than that of freedom, yet for practical purposes the footpath of freedom is the only one [456] upon which it is possible to make use of reason in our conduct. Therefore, it is just as impossible for the most subtle philosophy as for the most ordinary human reason to argue away freedom. Hence philosophy must assume that no real contradiction will be found between freedom and natural necessity in the same human actions, for it cannot give up the concept of nature any more than that of freedom.
Nevertheless, even though one might never be able to comprehend how freedom is possible, yet this apparent contradiction must at least be removed in a convincing manner. For if the thought of freedom contradicts itself or nature, which is equally necessary, then freedom would have to be completely given up in favor of natural necessity.
It would, however, be impossible to escape this contradiction if the subject, deeming himself free, were to think of himself in the same sense or in the very same relationship when he calls himself free as when he assumes himself subject to the law of nature regarding the same action. Therefore, an unavoidable problem of speculative philosophy is at least to show that its illusion regarding the contradiction rests on our thinking of man in a different sense and relation when we call him free from when we regard him as being a part of nature and hence as subject to the laws of nature. Hence it must show not only that both can coexist very well, but that both must be thought of as necessarily united in the same subject; for otherwise no explanation could be given as to why reason should be burdened with an idea which involves us in a perplexity that is sorely embarrassing to reason in its theoretic use, even though it may without contradiction be united with another idea that is sufficiently established. This duty, however, is Incumbent solely on speculative philosophy in order that it may clear the way for practical philosophy. Thus the philosopher has no option as to whether he will remove the apparent contradiction or leave it untouched; for in the latter case the theory regarding this could be bonum vacans, into the possession of which the fatalist can justifiably enter and chase all morality out of its supposed property as occupying it without title.
Nevertheless, one cannot here say as yet that the boundary of practical philosophy begins. For the settlement of the controversy does not belong to practical philosophy; the latter only requires speculative reason to put an end to the dissension in which it is entangled as regards theoretical [457] questions in order that practical reason may have rest and security from external attacks that might make disputable the ground upon which it wants to build.
The just claim to freedom of the will made even by ordinary human reason is founded on the consciousness and the admitted presupposition that reason is independent of mere subjective determination by causes which together make up what belongs only to sensation and comes under the general designation of sensibility. Regarding himself in this way as intelligence, man thereby puts himself into another order of things. And when he thinks of himself as intelligence endowed with a will and consequently with causality, he puts himself into relation with determining grounds of a kind altogether different from the kind when he perceives himself as a phenomenon in the world of sense (as he really is also) and subjects his causality to external determination according to laws of nature. Now he soon realizes that both can-and indeed must-hold good at the same time. For there is not the slightest contradiction involved in saying that a thing as appearance (belonging to the world of sense) is subject to certain laws, while it is independent of those laws when regarded as a thing or being in itself. That man must represent and think of himself in this two-fold way rests, on the one hand, upon the consciousness of himself as an object affected through the senses and, on the other hand, upon the consciousness of himself as intelligence, i.e., as Independent of sensuous impulses in his use of reason (and hence as belonging to the intelligible world).
And hence man claims that he has a will which reckons to his account nothing that belongs merely to his desires and inclinations, and which, on the contrary, thinks of actions that can be performed only by disregarding all desires and sensuous Incitements as being possible and as indeed being necessary for him. The causality of such actions lies in man as Intelligence and lies in the laws of such effects and actions as are in accordance with principles of an intelligible world, of which he knows nothing more than that in such a world reason alone, and indeed pure reason Independent of sensibility, gives the law. Furthermore, since he is in such a world his proper self only as Intelligence (whereas regarded as a human being he is merely an appearance of himself), those laws apply to him immediately and categorically. Consequently, Incitements from Inclinations and Impulses (and hence from the whole nature of the world of sense) cannot impair [458] the laws of his willing Insofar as he is intelligence. Indeed he does not even hold himself responsible for such inclinations and impulses or ascribe them to his proper self, i.e., his will, although he does ascribe to his will any Indulgence which he might extend to them if he allowed them any influence on his maxims to the detriment of the rational laws of his will.
When practical reason thinks itself into an intelligible world, it does not in the least thereby transcend its limits, as it would if it tried to enter it by intuition or sensation. The thought of an intelligible world is merely negative as regards the world of sense. The latter world does not give reason any laws for determining the will and is positive only in this single point, viz., it simultaneously combines freedom as negative determination with a positive faculty and even a causality of reason. This causality is designated as a will to act in such a way that the principle of actions may accord with the essential character of a rational cause, i.e., with the condition that the maxim of these actions have universal validity as a law. But if practical reason were to bring in an object of the will, i.e., a motive of action, from the intelligible world, then it would overstep its boundaries and pretend to be acquainted with something of which it knows nothing. The concept of an intelligible world is thus only a point of view which reason sees itself compelled to take outside of appearances in order to think of itself as practical. If the influences of sensibility were determining for man, reason would not be able to take this point of view, which is nonetheless necessary if he is not to be denied the consciousness of himself as Intelligence and hence as a rational cause that is active through reason, i.e., free in its operation. This thought certainly involves the idea of an order and a legislation different from that of the mechanism of nature which applies to the world of sense; and it makes necessary the concept of an intelligible world (i.e., the whole of rational beings as things in themselves). But it makes not the slightest claim to anything more than to think of such a world as regards merely its formal condition, i.e., the universality of the will’s maxims as laws and thus the will’s autonomy, which alone is consistent with freedom. On the contrary, all laws determined by reference to an object yield heteronomy, which can be found only in laws of nature and can apply only to the world of sense.
But reason would overstep all its bounds if it undertook to explain how [459] pure reason can be practical. This is exactly the same problem as explaining how freedom is possible.
For we can explain nothing but what we can reduce to laws whose object can be given in some possible experience. But freedom is a mere idea, whose objective reality can in no way be shown in accordance with laws of nature and consequently not in any possible experience. Therefore, the idea of freedom can never admit of comprehension or even of insight, because it cannot by any analogy have an example falling under it. It holds only as a necessary presupposition of reason in a being who believes himself conscious of a will, i.e., of a faculty distinct from mere desire (namely, a faculty of determining himself to action as intelligence and hence in accordance with laws of reason Independently of natural instincts). But where determination according to laws of nature ceases, there likewise ceases all explanation and nothing remains but defense, i.e., refutation of the objections of those who profess to have seen deeper Into the essence of things and thereupon boldly declare freedom to be impossible. One can only show them that their supposed discovery of a contradiction lies nowhere but here: In order to make the law of nature applicable to human actions, they have necessarily had to regard man as an appearance; and now when they are required to think of man qua Intelligence as thing in himself as well, they still persist in regarding him as appearance. In that case, to be sure, the exemption of man’s causality (i.e., his will) from all the natural laws of the world of sense would, as regards one and the same subject, give rise to a contradiction. But this disappears if they would but bethink themselves and admit, as is reasonable, that behind appearances there must lie as their ground also things in themselves (though hidden) and that the laws of their operations cannot be expected to be the same as those that govern their appearances.
The subjective Impossibility of explaining freedom of the will is the same as the Impossibility of discovering and explaining an interest? which man [460] can take in moral laws. Nevertheless, he does indeed take such an interest, the basis of which in us is called moral feeling. Some people have falsely construed this feeling to be the standard of our moral judgment, whereas it must rather be regarded as the subjective effect that the law exercises upon the will, while reason alone furnishes the objective grounds of such moral feeling.
In order to will what reason alone prescribes as an ought for sensuously affected rational beings, there certainly must be a power of reason to Infuse a feeling of pleasure or satisfaction in the fulfillment of duty, and hence there has to be a causality of reason to determine sensibility in accordance with rational principles. But it is quite impossible to discern, i.e., to make a priori conceivable, how a mere thought which itself contains nothing sensuous can produce a sensation of pleasure or displeasure. For here is a special kind of causality regarding which, as with all causality, we can determine nothing a priori but must consult experience alone. However, experience can provide us with no relation of cause and effect except between two objects of experience. But in this case pure reason by means of mere ideas (which furnish no object at all for experience) is to be the cause of an effect that admittedly lies in experience. Consequently, there is for us men no possibility at all for an explanation as to how and why the universality of a maxim as a law, and hence morality, Interests us. This much only is certain: the moral law is valid for us not because it interests us (for this is heteronomy and the dependence of practical reason [461] on sensibility, viz., on an underlying feeling whereby reason could never be morally legislative); but, rather, the moral law interests us because it is valid for us as men, since it has sprung from our will as intelligence and hence from our proper self. But what belongs to mere appearance is necessarily subordinated by reason to the nature of the thing in itself.
Thus the question as to how a categorical imperative is possible can be answered to the extent that there can be supplied the sole presupposition under which such an imperative is alone possible-namely, the idea of freedom. The necessity of this presupposition is discernible, and this much is sufficient for the practical use of reason, i.e., for being convinced as to the validity of this imperative, and hence also of the moral law; but how this presupposition itself is possible can never be discerned by any human reason. However, on the presupposition of freedom of the will of an intelligence, there necessarily follows the will’s autonomy as the formal condition under which alone the will can be determined. To presuppose this freedom of the will (without Involving any contradiction with the principle of natural necessity in the connection of appearances in the world of sense) is not only quite possible (as speculative philosophy can show), but is without any further condition also necessary for a rational being conscious of his causality through reason and hence conscious of a will (which is different from desires) as he makes such freedom in practice, i.e., in idea, the underlying condition of all his voluntary actions. But how pure reason can be practical by itself without other incentives taken from whatever source-i.e., how the mere principle of the universal validity of all reason’s maxims as laws (which would certainly be the form of a pure practical reason) can by itself, without any matter (object) of the will in which some antecedent interest might be taken, furnish an incentive and produce an interest which could be called purely moral; or, in other words, how pure reason could be practical: to explain all this is quite beyond the power of human reason, and all the effort and work of seeking such an explanation is wasted.
It is just the same as if I tried to find out how freedom itself is possible as [462] causality of a will. For I thereby leave the philosophical basis of explanation, and I have no other basis. Now I could indeed flutter about in the world of Intelligences, i.e., In the intelligible world still remaining to me. But even though I have an idea of such a world-an idea which has its own good grounds-yet I have not the slightest acquaintance with such a world and can never attain such acquaintance by all the efforts of my natural faculty of reason. This intelligible world signifies only a something that remains over when I have excluded from the determining grounds of my will everything that belongs to the world of sense, so as to restrict the principle of having all motives come from the field of sensibility. By so doing I set bounds to this field and show that it does not contain absolutely everything within itself but that beyond it there is still something more, regarding which, however, I have no further acquaintance. After the exclusion of all matter, i.e., cognition of objects, from pure reason which thinks this ideal, nothing remains over for me except such reason’s form, viz., the practical law of the universal validity of maxims; and in conformity with this law I think of reason in its relation to a pure intelligible world as a possible efficient cause, i.e., as a cause determining the will. An Incentive must in this case be wholly absent; this idea of an intelligible world would here have to be itself the Incentive or have to be that in which reason originally took an interest. But to make this conceivable is precisely the problem that we cannot solve.
Here then is the extreme limit of all moral Inquiry. To determine this limit is of great importance for the following considerations. On the one hand, reason should not, to the detriment of morals, search around in the world of sense for the supreme motive and for some interest that is conceivable but is nonetheless empirical. On the other hand, reason should not flap its wings impotently, without leaving the spot, in a space that for it is empty, namely, the space of transcendent concepts that is called the intelligible world, and thereby lose itself among mere phantoms of the brain. Furthermore, the idea of a pure intelligible world regarded as a whole of all intelligences to which we ourselves belong as rational beings (even though we are from another standpoint also members of the world of sense) remains always a useful and permissible idea for the purpose of a rational belief, although all knowledge ends at its boundary. This Idea produces in us a lively interest in the moral law by means of the splendid ideal of a universal kingdom of ends in themselves (rational beings), to which we can belong as members only if we carefully conduct ourselves [463] according to maxims of freedom as if they were laws of nature.
Concluding Remark
The speculative use of reason with regard to nature leads to the absolute necessity of some supreme cause of the world. The practical use of reason with reference to freedom leads also to absolute necessity, but only to the necessity of the laws of the actions of a rational being as such. Now it is an essential principle of all use of our reason to push its knowledge to a consciousness of its necessity (for without necessity there would be no rational knowledge). But there is an equally essential restriction of the same reason that it cannot have insight into the necessity either of what is or what does happen or of what should happen, unless there is presupposed a condition under which it is or does happen or should happen. In this way, however, the satisfaction of reason is only further and further postponed by the continual inquiry after the condition. Reason, therefore, restlessly seeks the unconditionally necessary and sees itself compelled to assume this without having any means of making such necessity conceivable; reason is happy enough if only it can find a concept which is compatible with this assumption. Hence there is no fault in our deduction of the supreme principle of morality, but rather a reproach which must be made against human reason generally, involved in the fact that reason cannot render conceivable the absolute necessity of an unconditioned practical law (such as the categorical imperative must be). Reason cannot be blamed for not being willing to explain this necessity by means of a condition, namely, by basing it on some underlying interest, because in that case the law would no longer be moral, i.e., a supreme law of freedom. And so even though we do not indeed grasp the practical unconditioned necessity of the moral imperative, we do nevertheless grasp its inconceivability. This is all that can be fairly asked of a philosophy which strives in its principles to reach the very limit of human reason.