Critique of Practical Reason

This work is called the Critique of Practical Reason, not of the pure practical reason, although its parallelism with the speculative critique would seem to require the latter term. The reason of this appears sufficiently from the treatise itself. Its business is to show that there is pure practical reason, and for this purpose it criticizes the entire practical faculty of reason. If it succeeds in this, it has no need to criticize the pure faculty itself in order to see whether reason in making such a claim does not presumptuously overstep itself (as is the case with the speculative reason). For if, as pure reason, it is actually practical, it proves its own reality and that of its concepts by fact, and all disputation against the possibility of its being real is futile.

With this faculty, transcendental freedom is also established; freedom, namely, in that absolute sense in which speculative reason required it in its use of the concept of causality in order to escape the antinomy into which it inevitably falls, when in the chain of cause and effect it tries to think the unconditioned. Speculative reason could only exhibit this concept (of freedom) problematically as not impossible to thought, without assuring it any objective reality, and merely lest the supposed impossibility of what it must at least allow to be thinkable should endanger its very being and plunge it into an abyss of scepticism.

Inasmuch as the reality of the concept of freedom is proved by an apodeictic law of practical reason, it is the keystone of the whole system of pure reason, even the speculative, and all other concepts (those of God and immortality) which, as being mere ideas, remain in it unsupported, now attach themselves to this concept, and by it obtain consistence and objective reality; that is to say, their possibility is proved by the fact that freedom actually exists, for this idea is revealed by the moral law.

Freedom, however, is the only one of all the ideas of the speculative reason of which we know the possibility a priori (without, however, understanding it), because it is the condition of the moral law which we know.* The ideas of God and immortality, however, are not conditions of the moral law, but only conditions of the necessary object of a will determined by this law; that is to say, conditions of the practical use of our pure reason. Hence, with respect to these ideas, we cannot affirm that we know and understand, I will not say the actuality, but even the possibility of them. However they are the conditions of the application of the morally determined will to its object, which is given to it a priori, viz., the summum bonum. Consequently in this practical point of view their possibility must be assumed, although we cannot theoretically know and understand it. To justify this assumption it is sufficient, in a practical point of view, that they contain no intrinsic impossibility (contradiction). Here we have what, as far as speculative reason is concerned, is a merely subjective principle of assent, which, however, is objectively valid for a reason equally pure but practical, and this principle, by means of the concept of freedom, assures objective reality and authority to the ideas of God and immortality. Nay, there is a subjective necessity (a need of pure reason) to assume them. Nevertheless the theoretical knowledge of reason is not hereby enlarged, but only the possibility is given, which heretofore was merely a problem and now becomes assertion, and thus the practical use of reason is connected with the elements of theoretical reason. And this need is not a merely hypothetical one for the arbitrary purposes of speculation, that we must assume something if we wish in speculation to carry reason to its utmost limits, but it is a need which has the force of law to assume something without which that cannot be which we must inevitably set before us as the aim of our action.

* Lest any one should imagine that he finds an inconsistency here when I call freedom the condition of the moral law, and hereafter maintain in the treatise itself that the moral law is the condition under which we can first become conscious of freedom, I will merely remark that freedom is the ratio essendi of the moral law, while the moral law is the ratio cognoscendi of freedom. For Pad not the moral law been previously distinctly thought in our reason, we should never consider ourselves justified in assuming such a thing as freedom, although it be not contradictory. But were there no freedom it would be impossible to trace the moral law in ourselves at all.

It would certainly be more satisfactory to our speculative reason if it could solve these problems for itself without this circuit and preserve the solution for practical use as a thing to be referred to, but in fact our faculty of speculation is not so well provided. Those who boast of such high knowledge ought not to keep it back, but to exhibit it publicly that it may be tested and appreciated. They want to prove: very good, let them prove; and the critical philosophy lays its arms at their feet as the victors. Quid statis? Nolint. Atqui licet esse beatis. As they then do not in fact choose to do so, probably because they cannot, we must take up these arms again in order to seek in the mortal use of reason, and to base on this, the notions of God, freedom, and immortality, the possibility of which speculation cannot adequately prove.

Here first is explained the enigma of the critical philosophy, viz.: how we deny objective reality to the supersensible use of the categories in speculation and yet admit this reality with respect to the objects of pure practical reason. This must at first seem inconsistent as long as this practical use is only nominally known. But when, by a thorough analysis of it, one becomes aware that the reality spoken of does not imply any theoretical determination of the categories and extension of our knowledge to the supersensible; but that what is meant is that in this respect an object belongs to them, because either they are contained in the necessary determination of the will a priori, or are inseparably connected with its object; then this inconsistency disappears, because the use we make of these concepts is different from what speculative reason requires. On the other hand, there now appears an unexpected and very satisfactory proof of the consistency of the speculative critical philosophy. For whereas it insisted that the objects of experience as such, including our own subject, have only the value of phenomena, while at the same time things in themselves must be supposed as their basis, so that not everything supersensible was to be regarded as a fiction and its concept as empty; so now practical reason itself, without any concert with the speculative, assures reality to a supersensible object of the category of causality, viz., freedom, although (as becomes a practical concept) only for practical use; and this establishes on the evidence of a fact that which in the former case could only be conceived. By this the strange but certain doctrine of the speculative critical philosophy, that the thinking subject is to itself in internal intuition only a phenomenon, obtains in the critical examination of the practical reason its full confirmation, and that so thoroughly that we should be compelled to adopt this doctrine, even if the former had never proved it at all.*

* The union of causality as freedom with causality as rational mechanism, the former established by the moral law, the latter by the law of nature in the same subject, namely, man, is impossible, unless we conceive him with reference to the former as a being in himself, and with reference to the latter as a phenomenon- the former in pure consciousness, the latter in empirical consciousness. Otherwise reason inevitably contradicts itself.

By this also I can understand why the most considerable objections which I have as yet met with against the Critique turn about these two points, namely, on the one side, the objective reality of the categories as applied to noumena, which is in the theoretical department of knowledge denied, in the practical affirmed; and on the other side, the paradoxical demand to regard oneself qua subject of freedom as a noumenon, and at the same time from the point of view of physical nature as a phenomenon in one's own empirical consciousness; for as long as one has formed no definite notions of morality and freedom, one could not conjecture on the one side what was intended to be the noumenon, the basis of the alleged phenomenon, and on the other side it seemed doubtful whether it was at all possible to form any notion of it, seeing that we had previously assigned all the notions of the pure understanding in its theoretical use exclusively to phenomena. Nothing but a detailed criticism of the practical reason can remove all this misapprehension and set in a clear light the consistency which constitutes its greatest merit.

So much by way of justification of the proceeding by which, in this work, the notions and principles of pure speculative reason which have already undergone their special critical examination are, now and then, again subjected to examination. This would not in other cases be in accordance with the systematic process by which a science is established, since matters which have been decided ought only to be cited and not again discussed. In this case, however, it was not only allowable but necessary, because reason is here considered in transition to a different use of these concepts from what it had made of them before. Such a transition necessitates a comparison of the old and the new usage, in order to distinguish well the new path from the old one and, at the same time, to allow their connection to be observed. Accordingly considerations of this kind, including those which are once more directed to the concept of freedom in the practical use of the pure reason, must not be regarded as an interpolation serving only to fill up the gaps in the critical system of speculative reason (for this is for its own purpose complete), or like the props and buttresses which in a hastily constructed building are often added afterwards; but as true members which make the connexion of the system plain, and show us concepts, here presented as real, which there could only be presented problematically. This remark applies especially to the concept of freedom, respecting which one cannot but observe with surprise that so many boast of being able to understand it quite well and to explain its possibility, while they regard it only psychologically, whereas if they had studied it in a transcendental point of view, they must have recognized that it is not only indispensable as a problematical concept, in the complete use of speculative reason, but also quite incomprehensible; and if they afterwards came to consider its practical use, they must needs have come to the very mode of determining the principles of this, to which they are now so loth to assent. The concept of freedom is the stone of stumbling for all empiricists, but at the same time the key to the loftiest practical principles for critical moralists, who perceive by its means that they must necessarily proceed by a rational method. For this reason I beg the reader not to pass lightly over what is said of this concept at the end of the Analytic.

I must leave it to those who are acquainted with works of this kind to judge whether such a system as that of the practical reason, which is here developed from the critical examination of it, has cost much or little trouble, especially in seeking not to miss the true point of view from which the whole can be rightly sketched. It presupposes, indeed, the Fundamental Principles of the Metaphysic of Morals, but only in so far as this gives a preliminary acquaintance with the principle of duty, and assigns and justifies a definite formula thereof; in other respects it is independent.* It results from the nature of this practical faculty itself that the complete classification of all practical sciences cannot be added, as in the critique of the speculative reason. For it is not possible to define duties specially, as human duties, with a view to their classification, until the subject of this definition (viz., man) is known according to his actual nature, at least so far as is necessary with respect to duty; this, however, does not belong to a critical examination of the practical reason, the business of which is only to assign in a complete manner the principles of its possibility, extent, and limits, without special reference to human nature. The classification then belongs to the system of science, not to the system of criticism.

* A reviewer who wanted to find some fault with this work has hit the truth better, perhaps, than he thought, when he says that no new principle of morality is set forth in it, but only a new formula. But who would think of introducing a new principle of all morality and making himself as it were the first discoverer of it, just as if all the world before him were ignorant what duty was or had been in thorough-going error? But whoever knows of what importance to a mathematician a formula is, which defines accurately what is to be done to work a problem, will not think that a formula is insignificant and useless which does the same for all duty in general.

In the second part of the Analytic I have given, as I trust, a sufficient answer to the objection of a truth-loving and acute critic* of the Fundamental Principles of the Metaphysic of Morals- a critic always worthy of respect the objection, namely, that the notion of good was not established before the moral principle, as be thinks it ought to have been.*[2] I have also had regard to many of the objections which have reached me from men who show that they have at heart the discovery of the truth, and I shall continue to do so (for those who have only their old system before their eyes, and who have already settled what is to be approved or disapproved, do not desire any explanation which might stand in the way of their own private opinion.)

It might also have been objected to me that I have not first defined the notion of the faculty of desire, or of the feeling of Pleasure, although this reproach would be unfair, because this definition might reasonably be presupposed as given in psychology. However, the definition there given might be such as to found the determination of the faculty of desire on the feeling of pleasure (as is commonly done), and thus the supreme principle of practical philosophy would be necessarily made empirical, which, however, remains to be proved and in this critique is altogether refuted. It will, therefore, give this definition here in such a manner as it ought to be given, in order to leave this contested point open at the beginning, as it should be. LIFE is the faculty a being has of acting according to laws of the faculty of desire. The faculty of DESIRE is the being's faculty of becoming by means of its ideas the cause of the actual existence of the objects of these ideas. PLEASURE is the idea of the agreement of the object, or the action with the subjective conditions of life, i.e., with the faculty of causality of an idea in respect of the actuality of its object (or with the determination of the forces of the subject to action which produces it). I have no further need for the purposes of this critique of notions borrowed from psychology; the critique itself supplies the rest. It is easily seen that the question whether the faculty of desire is always based on pleasure, or whether under certain conditions pleasure only follows the determination of desire, is by this definition left undecided, for it is composed only of terms belonging to the pure understanding, i.e., of categories which contain nothing empirical. Such precaution is very desirable in all philosophy and yet is often neglected; namely, not to prejudge questions by adventuring definitions before the notion has been completely analysed, which is often very late. It may be observed through the whole course of the critical philosophy (of the theoretical as well as the practical reason) that frequent opportunity offers of supplying defects in the old dogmatic method of philosophy, and of correcting errors which are not observed until we make such rational use of these notions viewing them as a whole.

When we have to study a particular faculty of the human mind in its sources, its content, and its limits; then from the nature of human knowledge we must begin with its parts, with an accurate and complete exposition of them; complete, namely, so far as is possible in the present state of our knowledge of its elements. But there is another thing to be attended to which is of a more philosophical and architectonic character, namely, to grasp correctly the idea of the whole, and from thence to get a view of all those parts as mutually related by the aid of pure reason, and by means of their derivation from the concept of the whole. This is only possible through the most intimate acquaintance with the system; and those who find the first inquiry too troublesome, and do not think it worth their while to attain such an acquaintance, cannot reach the second stage, namely, the general view, which is a synthetical return to that which had previously been given analytically. It is no wonder then if they find inconsistencies everywhere, although the gaps which these indicate are not in the system itself, but in their own incoherent train of thought.

I have no fear, as regards this treatise, of the reproach that I wish to introduce a new language, since the sort of knowledge here in question has itself somewhat of an everyday character. Nor even in the case of the former critique could this reproach occur to anyone who had thought it through and not merely turned over the leaves. To invent new words where the language has no lack of expressions for given notions is a childish effort to distinguish oneself from the crowd, if not by new and true thoughts, yet by new patches on the old garment. If, therefore, the readers of that work know any more familiar expressions which are as suitable to the thought as those seem to me to be, or if they think they can show the futility of these thoughts themselves and hence that of the expression, they would, in the first case, very much oblige me, for I only desire to be understood: and, in the second case, they would deserve well of philosophy. But, as long as these thoughts stand, I very much doubt that suitable and yet more common expressions for them can be found.*

* I am more afraid in the present treatise of occasional misconception in respect of some expressions which I have chosen with the greatest care in order that the notion to which they point may not be missed. Thus, in the table of categories of the Practical reason under the title of Modality, the Permitted, and forbidden (in a practical objective point of view, possible and impossible) have almost the same meaning in common language as the next category, duty and contrary to duty. Here, however, the former means what coincides with, or contradicts, a merely possible practical precept (for example, the solution of all problems of geometry and mechanics); the latter, what is similarly related to a law actually present in the reason; and this distinction is not quite foreign even to common language, although somewhat unusual. For example, it is forbidden to an orator, as such, to forge new words or constructions; in a certain degree this is permitted to a poet; in neither case is there any question of duty. For if anyone chooses to forfeit his reputation as an orator, no one can prevent him. We have here only to do with the distinction of imperatives into problematical, assertorial, and apodeictic. Similarly in the note in which I have pared the moral ideas of practical perfection in different philosophical schools, I have distinguished the idea of wisdom from that of holiness, although I have stated that essentially and objectively they are the same. But in that place I understand by the former only that wisdom to which man (the Stoic) lays claim; therefore I take it subjectively as an attribute alleged to belong to man. (Perhaps the expression virtue, with which also the made great show, would better mark the characteristic of his school.) The expression of a postulate of pure practical reason might give most occasion to misapprehension in case the reader confounded it with the signification of the postulates in pure mathematics, which carry apodeictic certainty with them. These, however, postulate the possibility of an action, the object of which has been previously recognized a priori in theory as possible, and that with perfect certainty. But the former postulates the possibility of an object itself (God and the immortality of the soul) from apodeictic practical laws, and therefore only for the purposes of a practical reason. This certainty of the postulated possibility then is not at all theoretic, and consequently not apodeictic; that is to say, it is not a known necessity as regards the object, but a necessary supposition as regards the subject, necessary for the obedience to its objective but practical laws. It is, therefore, merely a necessary hypothesis. I could find no better expression for this rational necessity, which is subjective, but yet true and unconditional.

In this manner, then, the a priori principles of two faculties of the mind, the faculty of cognition and that of desire, would be found and determined as to the conditions, extent, and limits of their use, and thus a sure foundation be paid for a scientific system of philosophy, both theoretic and practical.

Nothing worse could happen to these labours than that anyone should make the unexpected discovery that there neither is, nor can be, any a priori knowledge at all. But there is no danger of this. This would be the same thing as if one sought to prove by reason that there is no reason. For we only say that we know something by reason, when we are conscious that we could have known it, even if it had not been given to us in experience; hence rational knowledge and knowledge a priori are one and the same. It is a clear contradiction to try to extract necessity from a principle of experience (ex pumice aquam), and to try by this to give a judgement true universality (without which there is no rational inference, not even inference from analogy, which is at least a presumed universality and objective necessity). To substitute subjective necessity, that is, custom, for objective, which exists only in a priori judgements, is to deny to reason the power of judging about the object, i.e., of knowing it, and what belongs to it. It implies, for example, that we must not say of something which often or always follows a certain antecedent state that we can conclude from this to that (for this would imply objective necessity and the notion of an a priori connexion), but only that we may expect similar cases (just as animals do), that is that we reject the notion of cause altogether as false and a mere delusion. As to attempting to remedy this want of objective and consequently universal validity by saying that we can see no ground for attributing any other sort of knowledge to other rational beings, if this reasoning were valid, our ignorance would do more for the enlargement of our knowledge than all our meditation. For, then, on this very ground that we have no knowledge of any other rational beings besides man, we should have a right to suppose them to be of the same nature as we know ourselves to be: that is, we should really know them. I omit to mention that universal assent does not prove the objective validity of a judgement (i.e., its validity as a cognition), and although this universal assent should accidentally happen, it could furnish no proof of agreement with the object; on the contrary, it is the objective validity which alone constitutes the basis of a necessary universal consent.

Hume would be quite satisfied with this system of universal empiricism, for, as is well known, he desired nothing more than that, instead of ascribing any objective meaning to the necessity in the concept of cause, a merely subjective one should be assumed, viz., custom, in order to deny that reason could judge about God, freedom, and immortality; and if once his principles were granted, he was certainly well able to deduce his conclusions therefrom, with all logical coherence. But even Hume did not make his empiricism so universal as to include mathematics. He holds the principles of mathematics to be analytical; and if his were correct, they would certainly be apodeictic also: but we could not infer from this that reason has the faculty of forming apodeictic judgements in philosophy also- that is to say, those which are synthetical judgements, like the judgement of causality. But if we adopt a universal empiricism, then mathematics will be included.

Now if this science is in contradiction with a reason that admits only empirical principles, as it inevitably is in the antinomy in which mathematics prove the infinite divisibility of space, which empiricism cannot admit; then the greatest possible evidence of demonstration is in manifest contradiction with the alleged conclusions from experience, and we are driven to ask, like Cheselden's blind patient, "Which deceives me, sight or touch?" (for empiricism is based on a necessity felt, rationalism on a necessity seen). And thus universal empiricism reveals itself as absolute scepticism. It is erroneous to attribute this in such an unqualified sense to Hume,* since he left at least one certain touchstone (which can only be found in a priori principles), although experience consists not only of feelings, but also of judgements.

* Names that designate the followers of a sect have always been accompanied with much injustice; just as if one said, "N is an Idealist." For although he not only admits, but even insists, that our ideas of external things have actual objects of external things corresponding to them, yet he holds that the form of the intuition does not depend on them but on the human mind.

However, as in this philosophical and critical age such empiricism can scarcely be serious, and it is probably put forward only as an intellectual exercise and for the purpose of putting in a clearer light, by contrast, the necessity of rational a priori principles, we can only be grateful to those who employ themselves in this otherwise uninstructive labour.

Of the Idea of a Critique of Practical Reason

The theoretical use of reason was concerned with objects of the cognitive faculty only, and a critical examination of it with reference to this use applied properly only to the pure faculty of cognition; because this raised the suspicion, which was afterwards confirmed, that it might easily pass beyond its limits, and be lost among unattainable objects, or even contradictory notions. It is quite different with the practical use of reason. In this, reason is concerned with the grounds of determination of the will, which is a faculty either to produce objects corresponding to ideas, or to determine ourselves to the effecting of such objects (whether the physical power is sufficient or not); that is, to determine our causality. For here, reason can at least attain so far as to determine the will, and has always objective reality in so far as it is the volition only that is in question. The first question here then is whether pure reason of itself alone suffices to determine the will, or whether it can be a ground of determination only as dependent on empirical conditions. Now, here there comes in a notion of causality justified by the critique of the pure reason, although not capable of being presented empirically, viz., that of freedom; and if we can now discover means of proving that this property does in fact belong to the human will (and so to the will of all rational beings), then it will not only be shown that pure reason can be practical, but that it alone, and not reason empirically limited, is indubitably practical; consequently, we shall have to make a critical examination, not of pure practical reason, but only of practical reason generally. For when once pure reason is shown to exist, it needs no critical examination. For reason itself contains the standard for the critical examination of every use of it. The critique, then, of practical reason generally is bound to prevent the empirically conditioned reason from claiming exclusively to furnish the ground of determination of the will. If it is proved that there is a [practical] reason, its employment is alone immanent; the empirically conditioned use, which claims supremacy, is on the contrary transcendent and expresses itself in demands and precepts which go quite beyond its sphere. This is just the opposite of what might be said of pure reason in its speculative employment.

However, as it is still pure reason, the knowledge of which is here the foundation of its practical employment, the general outline of the classification of a critique of practical reason must be arranged in accordance with that of the speculative. We must, then, have the Elements and the Methodology of it; and in the former an Analytic as the rule of truth, and a Dialectic as the exposition and dissolution of the illusion in the judgements of practical reason. But the order in the subdivision of the Analytic will be the reverse of that in the critique of the pure speculative reason. For, in the present case, we shall commence with the principles and proceed to the concepts, and only then, if possible, to the senses; whereas in the case of the speculative reason we began with the senses and had to end with the principles. The reason of this lies again in this: that now we have to do with a will, and have to consider reason, not in its relation to objects, but to this will and its causality. We must, then, begin with the principles of a causality not empirically conditioned, after which the attempt can be made to establish our notions of the determining grounds of such a will, of their application to objects, and finally to the subject and its sense faculty. We necessarily begin with the law of causality from freedom, that is, with a pure practical principle, and this determines the objects to which alone it can be applied.

BOOK I. The Analytic of Pure Practical Reason
CHAPTER I. Of the Principles of Pure Practical Reason

Practical principles are propositions which contain a general determination of the will, having under it several practical rules. They are subjective, or maxims, when the condition is regarded by the subject as valid only for his own will, but are objective, or practical laws, when the condition is recognized as objective, that is, valid for the will of every rational being.


Supposing that pure reason contains in itself a practical motive, that is, one adequate to determine the will, then there are practical laws; otherwise all practical principles will be mere maxims. In case the will of a rational being is pathologically affected, there may occur a conflict of the maxims with the practical laws recognized by itself. For example, one may make it his maxim to let no injury pass unrevenged, and yet he may see that this is not a practical law, but only his own maxim; that, on the contrary, regarded as being in one and the same maxim a rule for the will of every rational being, it must contradict itself. In natural philosophy the principles of what happens, e.g., the principle of equality of action and reaction in the communication of motion) are at the same time laws of nature; for the use of reason there is theoretical and determined by the nature of the object. In practical philosophy, i.e., that which has to do only with the grounds of determination of the will, the principles which a man makes for himself are not laws by which one is inevitably bound; because reason in practical matters has to do with the subject, namely, with the faculty of desire, the special character of which may occasion variety in the rule. The practical rule is always a product of reason, because it prescribes action as a means to the effect. But in the case of a being with whom reason does not of itself determine the will, this rule is an imperative, i.e., a rule characterized by "shall," which expresses the objective necessitation of the action and signifies that, if reason completely determined the will, the action would inevitably take place according to this rule. Imperatives, therefore, are objectively valid, and are quite distinct from maxims, which are subjective principles. The former either determine the conditions of the causality of the rational being as an efficient cause, i.e., merely in reference to the effect and the means of attaining it; or they determine the will only, whether it is adequate to the effect or not. The former would be hypothetical imperatives, and contain mere precepts of skill; the latter, on the contrary, would be categorical, and would alone be practical laws. Thus maxims are principles, but not imperatives. Imperatives themselves, however, when they are conditional (i.e., do not determine the will simply as will, but only in respect to a desired effect, that is, when they are hypothetical imperatives), are practical precepts but not laws. Laws must be sufficient to determine the will as will, even before I ask whether I have power sufficient for a desired effect, or the means necessary to produce it; hence they are categorical: otherwise they are not laws at all, because the necessity is wanting, which, if it is to be practical, must be independent of conditions which are pathological and are therefore only contingently connected with the will. Tell a man, for example, that he must be industrious and thrifty in youth, in order that he may not want in old age; this is a correct and important practical precept of the will. But it is easy to see that in this case the will is directed to something else which it is presupposed that it desires; and as to this desire, we must leave it to the actor himself whether he looks forward to other resources than those of his own acquisition, or does not expect to be old, or thinks that in case of future necessity he will be able to make shift with little. Reason, from which alone can spring a rule involving necessity, does, indeed, give necessity to this precept (else it would not be an imperative), but this is a necessity dependent on subjective conditions, and cannot be supposed in the same degree in all subjects. But that reason may give laws it is necessary that it should only need to presuppose itself, because rules are objectively and universally valid only when they hold without any contingent subjective conditions, which distinguish one rational being from another. Now tell a man that he should never make a deceitful promise, this is a rule which only concerns his will, whether the purposes he may have can be attained thereby or not; it is the volition only which is to be determined a priori by that rule. If now it is found that this rule is practically right, then it is a law, because it is a categorical imperative. Thus, practical laws refer to the will only, without considering what is attained by its causality, and we may disregard this latter (as belonging to the world of sense) in order to have them quite pure.


All practical principles which presuppose an object (matter) of the faculty of desire as the ground of determination of the will are empirical and can furnish no practical laws.

By the matter of the faculty of desire I mean an object the realization of which is desired. Now, if the desire for this object precedes the practical rule and is the condition of our making it a principle, then I say (in the first place) this principle is in that case wholly empirical, for then what determines the choice is the idea of an object and that relation of this idea to the subject by which its faculty of desire is determined to its realization. Such a relation to the subject is called the pleasure in the realization of an object. This, then, must be presupposed as a condition of the possibility of determination of the will. But it is impossible to know a priori of any idea of an object whether it will be connected with pleasure or pain, or be indifferent. In such cases, therefore, the determining principle of the choice must be empirical and, therefore, also the practical material principle which presupposes it as a condition.

In the second place, since susceptibility to a pleasure or pain can be known only empirically and cannot hold in the same degree for all rational beings, a principle which is based on this subjective condition may serve indeed as a maxim for the subject which possesses this susceptibility, but not as a law even to him (because it is wanting in objective necessity, which must be recognized a priori); it follows, therefore, that such a principle can never furnish a practical law.


All material practical principles as such are of one and the same kind and come under the general principle of self-love or private happiness.

Pleasure arising from the idea of the idea of the existence of a thing, in so far as it is to determine the desire of this thing, is founded on the susceptibility of the subject, since it depends on the presence of an object; hence it belongs to sense (feeling), and not to understanding, which expresses a relation of the idea to an object according to concepts, not to the subject according to feelings. It is, then, practical only in so far as the faculty of desire is determined by the sensation of agreeableness which the subject expects from the actual existence of the object. Now, a rational being's consciousness of the pleasantness of life uninterruptedly accompanying his whole existence is happiness; and the principle which makes this the supreme ground of determination of the will is the principle of self-love. All material principles, then, which place the determining ground of the will in the pleasure or pain to be received from the existence of any object are all of the same kind, inasmuch as they all belong to the principle of self-love or private happiness.


All material practical rules place the determining principle of the will in the lower desires; and if there were no purely formal laws of the will adequate to determine it, then we could not admit any higher desire at all.


It is surprising that men, otherwise acute, can think it possible to distinguish between higher and lower desires, according as the ideas which are connected with the feeling of pleasure have their origin in the senses or in the understanding; for when we inquire what are the determining grounds of desire, and place them in some expected pleasantness, it is of no consequence whence the idea of this pleasing object is derived, but only how much it pleases. Whether an idea has its seat and source in the understanding or not, if it can only determine the choice by presupposing a feeling of pleasure in the subject, it follows that its capability of determining the choice depends altogether on the nature of the inner sense, namely, that this can be agreeably affected by it. However dissimilar ideas of objects may be, though they be ideas of the understanding, or even of the reason in contrast to ideas of sense, yet the feeling of pleasure, by means of which they constitute the determining principle of the will (the expected satisfaction which impels the activity to the production of the object), is of one and the same kind, not only inasmuch as it can only be known empirically, but also inasmuch as it affects one and the same vital force which manifests itself in the faculty of desire, and in this respect can only differ in degree from every other ground of determination. Otherwise, how could we compare in respect of magnitude two principles of determination, the ideas of which depend upon different faculties, so as to prefer that which affects the faculty of desire in the highest degree. The same man may return unread an instructive book which he cannot again obtain, in order not to miss a hunt; he may depart in the midst of a fine speech, in order not to be late for dinner; he may leave a rational conversation, such as he otherwise values highly, to take his place at the gaming-table; he may even repulse a poor man whom he at other times takes pleasure in benefiting, because he has only just enough money in his pocket to pay for his admission to the theatre. If the determination of his will rests on the feeling of the agreeableness or disagreeableness that he expects from any cause, it is all the same to him by what sort of ideas he will be affected. The only thing that concerns him, in order to decide his choice, is, how great, how long continued, how easily obtained, and how often repeated, this agreeableness is. just as to the man who wants money to spend, it is all the same whether the gold was dug out of the mountain or washed out of the sand, provided it is everywhere accepted at the same value; so the man who cares only for the enjoyment of life does not ask whether the ideas are of the understanding or the senses, but only how much and how great pleasure they will give for the longest time. It is only those that would gladly deny to pure reason the power of determining the will, without the presupposition of any feeling, who could deviate so far from their own exposition as to describe as quite heterogeneous what they have themselves previously brought under one and the same principle. Thus, for example, it is observed that we can find pleasure in the mere exercise of power, in the consciousness of our strength of mind in overcoming obstacles which are opposed to our designs, in the culture of our mental talents, etc.; and we justly call these more refined pleasures and enjoyments, because they are more in our power than others; they do not wear out, but rather increase the capacity for further enjoyment of them, and while they delight they at the same time cultivate. But to say on this account that they determine the will in a different way and not through sense, whereas the possibility of the pleasure presupposes a feeling for it implanted in us, which is the first condition of this satisfaction; this is just as when ignorant persons that like to dabble in metaphysics imagine matter so subtle, so supersubtle that they almost make themselves giddy with it, and then think that in this way they have conceived it as a spiritual and yet extended being. If with Epicurus we make virtue determine the will only by means of the pleasure it promises, we cannot afterwards blame him for holding that this pleasure is of the same kind as those of the coarsest senses. For we have no reason whatever to charge him with holding that the ideas by which this feeling is excited in us belong merely to the bodily senses. As far as can be conjectured, he sought the source of many of them in the use of the higher cognitive faculty, but this did not prevent him, and could not prevent him, from holding on the principle above stated, that the pleasure itself which those intellectual ideas give us, and by which alone they can determine the will, is just of the same kind. Consistency is the highest obligation of a philosopher, and yet the most rarely found. The ancient Greek schools give us more examples of it than we find in our syncretistic age, in which a certain shallow and dishonest system of compromise of contradictory principles is devised, because it commends itself better to a public which is content to know something of everything and nothing thoroughly, so as to please every party.

The principle of private happiness, however much understanding and reason may be used in it, cannot contain any other determining principles for the will than those which belong to the lower desires; and either there are no [higher] desires at all, or pure reason must of itself alone be practical; that is, it must be able to determine the will by the mere form of the practical rule without supposing any feeling, and consequently without any idea of the pleasant or unpleasant, which is the matter of the desire, and which is always an empirical condition of the principles. Then only, when reason of itself determines the will (not as the servant of the inclination), it is really a higher desire to which that which is pathologically determined is subordinate, and is really, and even specifically, distinct from the latter, so that even the slightest admixture of the motives of the latter impairs its strength and superiority; just as in a mathematical demonstration the least empirical condition would degrade and destroy its force and value. Reason, with its practical law, determines the will immediately, not by means of an intervening feeling of pleasure or pain, not even of pleasure in the law itself, and it is only because it can, as pure reason, be practical, that it is possible for it to be legislative.


To be happy is necessarily the wish of every finite rational being, and this, therefore, is inevitably a determining principle of its faculty of desire. For we are not in possession originally of satisfaction with our whole existence- a bliss which would imply a consciousness of our own independent self-sufficiency this is a problem imposed upon us by our own finite nature, because we have wants and these wants regard the matter of our desires, that is, something that is relative to a subjective feeling of pleasure or pain, which determines what we need in order to be satisfied with our condition. But just because this material principle of determination can only be empirically known by the subject, it is impossible to regard this problem as a law; for a law being objective must contain the very same principle of determination of the will in all cases and for all rational beings. For, although the notion of happiness is in every case the foundation of practical relation of the objects to the desires, yet it is only a general name for the subjective determining principles, and determines nothing specifically; whereas this is what alone we are concerned with in this practical problem, which cannot be solved at all without such specific determination. For it is every man's own special feeling of pleasure and pain that decides in what he is to place his happiness, and even in the same subject this will vary with the difference of his wants according as this feeling changes, and thus a law which is subjectively necessary (as a law of nature) is objectively a very contingent practical principle, which can and must be very different in different subjects and therefore can never furnish a law; since, in the desire for happiness it is not the form (of conformity to law) that is decisive, but simply the matter, namely, whether I am to expect pleasure in following the law, and how much. Principles of self-love may, indeed, contain universal precepts of skill (how to find means to accomplish one's purpose), but in that case they are merely theoretical principles;* as, for example, how he who would like to eat bread should contrive a mill; but practical precepts founded on them can never be universal, for the determining principle of the desire is based on the feeling pleasure and pain, which can never be supposed to be universally directed to the same objects.

* Propositions which in mathematics or physics are called practical ought properly to be called technical. For they have nothing to do with the determination of the theoretical they only point out how the certain must is to be produced and are, therefore, just as theoretical as any propositions which express the connection of a cause with an effect. Now whoever chooses the effect must also choose the cause.

Even supposing, however, that all finite rational beings were thoroughly agreed as to what were the objects of their feelings of pleasure and pain, and also as to the means which they must employ to attain the one and avoid the other; still, they could by no means set up the principle of self-love as a practical law, for this unanimity itself would be only contingent. The principle of determination would still be only subjectively valid and merely empirical, and would not possess the necessity which is conceived in every law, namely, an objective necessity arising from a priori grounds; unless, indeed, we hold this necessity to be not at all practical, but merely physical, viz., that our action is as inevitably determined by our inclination, as yawning when we see others yawn. It would be better to maintain that there are no practical laws at all, but only counsels for the service of our desires, than to raise merely subjective principles to the rank of practical laws, which have objective necessity, and not merely subjective, and which must be known by reason a priori, not by experience (however empirically universal this may be). Even the rules of corresponding phenomena are only called laws of nature (e.g., the mechanical laws), when we either know them really a priori, or (as in the case of chemical laws) suppose that they would be known a priori from objective grounds if our insight reached further. But in the case of merely subjective practical principles, it is expressly made a condition that they rest, not on objective, but on subjective conditions of choice, and hence that they must always be represented as mere maxims, never as practical laws. This second remark seems at first sight to be mere verbal refinement, but it defines the terms of the most important distinction which can come into consideration in practical investigations.


A rational being cannot regard his maxims as practical universal laws, unless he conceives them as principles which determine the will, not by their matter, but by their form only.

By the matter of a practical principle I mean the object of the will. This object is either the determining ground of the will or it is not. In the former case the rule of the will is subjected to an empirical condition (viz., the relation of the determining idea to the feeling of pleasure and pain), consequently it can not be a practical law. Now, when we abstract from a law all matter, i.e., every object of the will (as a determining principle), nothing is left but the mere form of a universal legislation. Therefore, either a rational being cannot conceive his subjective practical principles, that is, his maxims, as being at the same time universal laws, or he must suppose that their mere form, by which they are fitted for universal legislation, is alone what makes them practical laws.


The commonest understanding can distinguish without instruction what form of maxim is adapted for universal legislation, and what is not. Suppose, for example, that I have made it my maxim to increase my fortune by every safe means. Now, I have a deposit in my hands, the owner of which is dead and has left no writing about it. This is just the case for my maxim. I desire then to know whether that maxim can also bold good as a universal practical law. I apply it, therefore, to the present case, and ask whether it could take the form of a law, and consequently whether I can by my maxim at the same time give such a law as this, that everyone may deny a deposit of which no one can produce a proof. I at once become aware that such a principle, viewed as a law, would annihilate itself, because the result would be that there would be no deposits. A practical law which I recognise as such must be qualified for universal legislation; this is an identical proposition and, therefore, self-evident. Now, if I say that my will is subject to a practical law, I cannot adduce my inclination (e.g., in the present case my avarice) as a principle of determination fitted to be a universal practical law; for this is so far from being fitted for a universal legislation that, if put in the form of a universal law, it would destroy itself.

It is, therefore, surprising that intelligent men could have thought of calling the desire of happiness a universal practical law on the ground that the desire is universal, and, therefore, also the maxim by which everyone makes this desire determine his will. For whereas in other cases a universal law of nature makes everything harmonious; here, on the contrary, if we attribute to the maxim the universality of a law, the extreme opposite of harmony will follow, the greatest opposition and the complete destruction of the maxim itself and its purpose. For, in that case, the will of all has not one and the same object, but everyone has his own (his private welfare), which may accidentally accord with the purposes of others which are equally selfish, but it is far from sufficing for a law; because the occasional exceptions which one is permitted to make are endless, and cannot be definitely embraced in one universal rule. In this manner, then, results a harmony like that which a certain satirical poem depicts as existing between a married couple bent on going to ruin, "O, marvellous harmony, what he wishes, she wishes also"; or like what is said of the pledge of Francis I to the Emperor Charles V, "What my brother Charles wishes that I wish also" (viz., Milan). Empirical principles of determination are not fit for any universal external legislation, but just as little for internal; for each man makes his own subject the foundation of his inclination, and in the same subject sometimes one inclination, sometimes another, has the preponderance. To discover a law which would govern them all under this condition, namely, bringing them all into harmony, is quite impossible.


Supposing that the mere legislative form of maxims is alone the sufficient determining principle of a will, to find the nature of the will which can be determined by it alone.

Since the bare form of the law can only be conceived by reason, and is, therefore, not an object of the senses, and consequently does not belong to the class of phenomena, it follows that the idea of it, which determines the will, is distinct from all the principles that determine events in nature according to the law of causality, because in their case the determining principles must themselves be phenomena. Now, if no other determining principle can serve as a law for the will except that universal legislative form, such a will must be conceived as quite independent of the natural law of phenomena in their mutual relation, namely, the law of causality; such independence is called freedom in the strictest, that is, in the transcendental, sense; consequently, a will which can have its law in nothing but the mere legislative form of the maxim is a free will.


Supposing that a will is free, to find the law which alone is competent to determine it necessarily.

Since the matter of the practical law, i.e., an object of the maxim, can never be given otherwise than empirically, and the free will is independent on empirical conditions (that is, conditions belonging to the world of sense) and yet is determinable, consequently a free will must find its principle of determination in the law, and yet independently of the matter of the law. But, besides the matter of the law, nothing is contained in it except the legislative form. It is the legislative form, then, contained in the maxim, which can alone constitute a principle of determination of the [free] will.


Thus freedom and an unconditional practical law reciprocally imply each other. Now I do not ask here whether they are in fact distinct, or whether an unconditioned law is not rather merely the consciousness of a pure practical reason and the latter identical with the positive concept of freedom; I only ask, whence begins our knowledge of the unconditionally practical, whether it is from freedom or from the practical law? Now it cannot begin from freedom, for of this we cannot be immediately conscious, since the first concept of it is negative; nor can we infer it from experience, for experience gives us the knowledge only of the law of phenomena, and hence of the mechanism of nature, the direct opposite of freedom. It is therefore the moral law, of which we become directly conscious (as soon as we trace for ourselves maxims of the will), that first presents itself to us, and leads directly to the concept of freedom, inasmuch as reason presents it as a principle of determination not to be outweighed by any sensible conditions, nay, wholly independent of them. But how is the consciousness, of that moral law possible? We can become conscious of pure practical laws just as we are conscious of pure theoretical principles, by attending to the necessity with which reason prescribes them and to the elimination of all empirical conditions, which it directs. The concept of a pure will arises out of the former, as that of a pure understanding arises out of the latter. That this is the true subordination of our concepts, and that it is morality that first discovers to us the notion of freedom, hence that it is practical reason which, with this concept, first proposes to speculative reason the most insoluble problem, thereby placing it in the greatest perplexity, is evident from the following consideration: Since nothing in phenomena can be explained by the concept of freedom, but the mechanism of nature must constitute the only clue; moreover, when pure reason tries to ascend in the series of causes to the unconditioned, it falls into an antinomy which is entangled in incomprehensibilities on the one side as much as the other; whilst the latter (namely, mechanism) is at least useful in the explanation of phenomena, therefore no one would ever have been so rash as to introduce freedom into science, had not the moral law, and with it practical reason, come in and forced this notion upon us. Experience, however, confirms this order of notions. Suppose some one asserts of his lustful appetite that, when the desired object and the opportunity are present, it is quite irresistible. [Ask him]- if a gallows were erected before the house where he finds this opportunity, in order that he should be hanged thereon immediately after the gratification of his lust, whether he could not then control his passion; we need not be long in doubt what he would reply. Ask him, however- if his sovereign ordered him, on pain of the same immediate execution, to bear false witness against an honourable man, whom the prince might wish to destroy under a plausible pretext, would he consider it possible in that case to overcome his love of life, however great it may be. He would perhaps not venture to affirm whether he would do so or not, but he must unhesitatingly admit that it is possible to do so. He judges, therefore, that he can do a certain thing because he is conscious that he ought, and he recognizes that he is free- a fact which but for the moral law he would never have known.


Act so that the maxim of thy will can always at the same time hold good as a principle of universal legislation.


Pure geometry has postulates which are practical propositions, but contain nothing further than the assumption that we can do something if it is required that we should do it, and these are the only geometrical propositions that concern actual existence. They are, then, practical rules under a problematical condition of the will; but here the rule says: We absolutely must proceed in a certain manner. The practical rule is, therefore, unconditional, and hence it is conceived a priori as a categorically practical proposition by which the will is objectively determined absolutely and immediately (by the practical rule itself, which thus is in this case a law); for pure reason practical of itself is here directly legislative. The will is thought as independent on empirical conditions, and, therefore, as pure will determined by the mere form of the law, and this principle of determination is regarded as the supreme condition of all maxims. The thing is strange enough, and has no parallel in all the rest of our practical knowledge. For the a priori thought of a possible universal legislation which is therefore merely problematical, is unconditionally commanded as a law without borrowing anything from experience or from any external will. This, however, is not a precept to do something by which some desired effect can be attained (for then the will would depend on physical conditions), but a rule that determines the will a priori only so far as regards the forms of its maxims; and thus it is at least not impossible to conceive that a law, which only applies to the subjective form of principles, yet serves as a principle of determination by means of the objective form of law in general. We may call the consciousness of this fundamental law a fact of reason, because we cannot reason it out from antecedent data of reason, e.g., the consciousness of freedom (for this is not antecedently given), but it forces itself on us as a synthetic a priori proposition, which is not based on any intuition, either pure or empirical. It would, indeed, be analytical if the freedom of the will were presupposed, but to presuppose freedom as a positive concept would require an intellectual intuition, which cannot here be assumed; however, when we regard this law as given, it must be observed, in order not to fall into any misconception, that it is not an empirical fact, but the sole fact of the pure reason, which thereby announces itself as originally legislative (sic volo, sic jubeo).


Pure reason is practical of itself alone and gives (to man) a universal law which we call the moral law.


The fact just mentioned is undeniable. It is only necessary to analyse the judgement that men pass on the lawfulness of their actions, in order to find that, whatever inclination may say to the contrary, reason, incorruptible and selfconstrained, always confronts the maxim of the will in any action with the pure will, that is, with itself, considering itself as a priori practical. Now this principle of morality, just on account of the universality of the legislation which makes it the formal supreme determining principle of the will, without regard to any subjective differentes, is declared by the reason to be a law for all rational beings, in so far as they have a will, that is, a power to determine their causality by the conception of rules; and, therefore, so far as they are capable of acting according to principles, and consequently also according to practical a priori principles (for these alone have the necessity that reason requires in a principle). It is, therefore, not limited to men only, but applies to all finite beings that possess reason and will; nay, it even includes the Infinite Being as the supreme intelligence. In the former case, however, the law has the form of an imperative, because in them, as rational beings, we can suppose a pure will, but being creatures affected with wants and physical motives, not a holy will, that is, one which would be incapable of any maxim conflicting with the moral law. In their case, therefore, the moral law is an imperative, which commands categorically, because the law is unconditioned; the relation of such a will to this law is dependence under the name of obligation, which implies a constraint to an action, though only by reason and its objective law; and this action is called duty, because an elective will, subject to pathological affections (though not determined by them, and, therefore, still free), implies a wish that arises from subjective causes and, therefore, may often be opposed to the pure objective determining principle; whence it requires the moral constraint of a resistance of the practical reason, which may be called an internal, but intellectual, compulsion. In the supreme intelligence the elective will is rightly conceived as incapable of any maxim which could not at the same time be objectively a law; and the notion of holiness, which on that account belongs to it, places it, not indeed above all practical laws, but above all practically restrictive laws, and consequently above obligation and duty. This holiness of will is, however, a practical idea, which must necessarily serve as a type to which finite rational beings can only approximate indefinitely, and which the pure moral law, which is itself on this account called holy, constantly and rightly holds before their eyes. The utmost that finite practical reason can effect is to be certain of this indefinite progress of one's maxims and of their steady disposition to advance. This is virtue, and virtue, at least as a naturally acquired faculty, can never be perfect, because assurance in such a case never becomes apodeictic certainty and, when it only amounts to persuasion, is very dangerous.


The autonomy of the will is the sole principle of all moral laws and of all duties which conform to them; on the other hand, heteronomy of the elective will not only cannot be the basis of any obligation, but is, on the contrary, opposed to the principle thereof and to the morality of the will.

In fact the sole principle of morality consists in the independence on all matter of the law (namely, a desired object), and in the determination of the elective will by the mere universal legislative form of which its maxim must be capable. Now this independence is freedom in the negative sense, and this self-legislation of the pure, and therefore practical, reason is freedom in the positive sense. Thus the moral law expresses nothing else than the autonomy of the pure practical reason; that is, freedom; and this is itself the formal condition of all maxims, and on this condition only can they agree with the supreme practical law. If therefore the matter of the volition, which can be nothing else than the object of a desire that is connected with the law, enters into the practical law, as the condition of its possibility, there results heteronomy of the elective will, namely, dependence on the physical law that we should follow some impulse or inclination. In that case the will does not give itself the law, but only the precept how rationally to follow pathological law; and the maxim which, in such a case, never contains the universally legislative form, not only produces no obligation, but is itself opposed to the principle of a pure practical reason and, therefore, also to the moral disposition, even though the resulting action may be conformable to the law.


Hence a practical precept, which contains a material (and therefore empirical) condition, must never be reckoned a practical law. For the law of the pure will, which is free, brings the will into a sphere quite different from the empirical; and as the necessity involved in the law is not a physical necessity, it can only consist in the formal conditions of the possibility of a law in general. All the matter of practical rules rests on subjective conditions, which give them only a conditional universality (in case I desire this or that, what I must do in order to obtain it), and they all turn on the principle of private happiness. Now, it is indeed undeniable that every volition must have an object, and therefore a matter; but it does not follow that this is the determining principle and the condition of the maxim; for, if it is so, then this cannot be exhibited in a universally legislative form, since in that case the expectation of the existence of the object would be the determining cause of the choice, and the volition must presuppose the dependence of the faculty of desire on the existence of something; but this dependence can only be sought in empirical conditions and, therefore, can never furnish a foundation for a necessary and universal rule. Thus, the happiness of others may be the object of the will of a rational being. But if it were the determining principle of the maxim, we must assume that we find not only a rational satisfaction in the welfare of others, but also a want such as the sympathetic disposition in some men occasions. But I cannot assume the existence of this want in every rational being (not at all in God). The matter, then, of the maxim may remain, but it must not be the condition of it, else the maxim could not be fit for a law. Hence, the mere form of law, which limits the matter, must also be a reason for adding this matter to the will, not for presupposing it. For example, let the matter be my own happiness. This (rule), if I attribute it to everyone (as, in fact, I may, in the case of every finite being), can become an objective practical law only if I include the happiness of others. Therefore, the law that we should promote the happiness of others does not arise from the assumption that this is an object of everyone's choice, but merely from this, that the form of universality which reason requires as the condition of giving to a maxim of self-love the objective validity of a law is the principle that determines the will. Therefore it was not the object (the happiness of others) that determined the pure will, but it was the form of law only, by which I restricted my maxim, founded on inclination, so as to give it the universality of a law, and thus to adapt it to the practical reason; and it is this restriction alone, and not the addition of an external spring, that can give rise to the notion of the obligation to extend the maxim of my self-love to the happiness of others.


The direct opposite of the principle of morality is, when the principle of private happiness is made the determining principle of the will, and with this is to be reckoned, as I have shown above, everything that places the determining principle which is to serve as a law, anywhere but in the legislative form of the maxim. This contradiction, however, is not merely logical, like that which would arise between rules empirically conditioned, if they were raised to the rank of necessary principles of cognition, but is practical, and would ruin morality altogether were not the voice of reason in reference to the will so clear, so irrepressible, so distinctly audible, even to the commonest men. It can only, indeed, be maintained in the perplexing speculations of the schools, which are bold enough to shut their ears against that heavenly voice, in order to support a theory that costs no trouble.

Suppose that an acquaintance whom you otherwise liked were to attempt to justify himself to you for having borne false witness, first by alleging the, in his view, sacred duty of consulting his own happiness; then by enumerating the advantages which he had gained thereby, pointing out the prudence he had shown in securing himself against detection, even by yourself, to whom he now reveals the secret, only in order that he may be able to deny it at any time; and suppose he were then to affirm, in all seriousness, that he has fulfilled a true human duty; you would either laugh in his face, or shrink back from him with disgust; and yet, if a man has regulated his principles of action solely with a view to his own advantage, you would have nothing whatever to object against this mode of proceeding. Or suppose some one recommends you a man as steward, as a man to whom you can blindly trust all your affairs; and, in order to inspire you with confidence, extols him as a prudent man who thoroughly understands his own interest, and is so indefatigably active that he lets slip no opportunity of advancing it; lastly, lest you should be afraid of finding a vulgar selfishness in him, praises the good taste with which he lives; not seeking his pleasure in money-making, or in coarse wantonness, but in the enlargement of his knowledge, in instructive intercourse with a select circle, and even in relieving the needy; while as to the means (which, of course, derive all their value from the end), he is not particular, and is ready to use other people's money for the purpose as if it were his own, provided only he knows that he can do so safely, and without discovery; you would either believe that the recommender was mocking you, or that he had lost his senses. So sharply and clearly marked are the boundaries of morality and self-love that even the commonest eye cannot fail to distinguish whether a thing belongs to the one or the other. The few remarks that follow may appear superfluous where the truth is so plain, but at least they may serve to give a little more distinctness to the judgement of common sense.

The principle of happiness may, indeed, furnish maxims, but never such as would be competent to be laws of the will, even if universal happiness were made the object. For since the knowledge of this rests on mere empirical data, since every man's judgement on it depends very much on his particular point of view, which is itself moreover very variable, it can supply only general rules, not universal; that is, it can give rules which on the average will most frequently fit, but not rules which must hold good always and necessarily; hence, no practical laws can be founded on it. Just because in this case an object of choice is the foundation of the rule and must therefore precede it, the rule can refer to nothing but what is [felt], and therefore it refers to experience and is founded on it, and then the variety of judgement must be endless. This principle, therefore, does not prescribe the same practical rules to all rational beings, although the rules are all included under a common title, namely, that of happiness. The moral law, however, is conceived as objectively necessary, only because it holds for everyone that has reason and will.

The maxim of self-love (prudence) only advises; the law of morality commands. Now there is a great difference between that which we are advised to do and that to which we are obliged.

The commonest intelligence can easily and without hesitation see what, on the principle of autonomy of the will, requires to be done; but on supposition of heteronomy of the will, it is bard and requires knowledge of the world to see what is to be done. That is to say, what duty is, is plain of itself to everyone; but what is to bring true durable advantage, such as will extend to the whole of one's existence, is always veiled in impenetrable obscurity; and much prudence is required to adapt the practical rule founded on it to the ends of life, even tolerably, by making proper exceptions. But the moral law commands the most punctual obedience from everyone; it must, therefore, not be so difficult to judge what it requires to be done, that the commonest unpractised understanding, even without worldly prudence, should fail to apply it rightly.

It is always in everyone's power to satisfy the categorical command of morality; whereas it is seldom possible, and by no means so to everyone, to satisfy the empirically conditioned precept of happiness, even with regard to a single purpose. The reason is that in the former case there is question only of the maxim, which must be genuine and pure; but in the latter case there is question also of one's capacity and physical power to realize a desired object. A command that everyone should try to make himself happy would be foolish, for one never commands anyone to do what he of himself infallibly wishes to do. We must only command the means, or rather supply them, since he cannot do everything that he wishes. But to command morality under the name of duty is quite rational; for, in the first place, not everyone is willing to obey its precepts if they oppose his inclinations; and as to the means of obeying this law, these need not in this case be taught, for in this respect whatever he wishes to do be can do.

He who has lost at play may be vexed at himself and his folly, but if he is conscious of having cheated at play (although he has gained thereby), he must despise himself as soon as he compares himself with the moral law. This must, therefore, be something different from the principle of private happiness. For a man must have a different criterion when he is compelled to say to himself: "I am a worthless fellow, though I have filled my purse"; and when he approves himself, and says: "I am a prudent man, for I have enriched my treasure."

Finally, there is something further in the idea of our practical reason, which accompanies the transgression of a moral law- namely, its ill desert. Now the notion of punishment, as such, cannot be united with that of becoming a partaker of happiness; for although he who inflicts the punishment may at the same time have the benevolent purpose of directing this punishment to this end, yet it must first be justified in itself as punishment, i.e., as mere harm, so that if it stopped there, and the person punished could get no glimpse of kindness hidden behind this harshness, he must yet admit that justice was done him, and that his reward was perfectly suitable to his conduct. In every punishment, as such, there must first be justice, and this constitutes the essence of the notion. Benevolence may, indeed, be united with it, but the man who has deserved punishment has not the least reason to reckon upon this. Punishment, then, is a physical evil, which, though it be not connected with moral evil as a natural consequence, ought to be connected with it as a consequence by the principles of a moral legislation. Now, if every crime, even without regarding the physical consequence with respect to the actor, is in itself punishable, that is, forfeits happiness (at least partially), it is obviously absurd to say that the crime consisted just in this, that be has drawn punishment on himself, thereby injuring his private happiness (which, on the principle of self-love, must be the proper notion of all crime). According to this view, the punishment would be the reason for calling anything a crime, and justice would, on the contrary, consist in omitting all punishment, and even preventing that which naturally follows; for, if this were done, there would no longer be any evil in the action, since the harm which otherwise followed it, and on account of which alone the action was called evil, would now be prevented. To look, however, on all rewards and punishments as merely the machinery in the hand of a higher power, which is to serve only to set rational creatures striving after their final end (happiness), this is to reduce the will to a mechanism destructive of freedom; this is so evident that it need not detain us.

More refined, though equally false, is the theory of those who suppose a certain special moral sense, which sense and not reason determines the moral law, and in consequence of which the consciousness of virtue is supposed to be directly connected with contentment and pleasure; that of vice, with mental dissatisfaction and pain; thus reducing the whole to the desire of private happiness. Without repeating what has been said above, I will here only remark the fallacy they fall into. In order to imagine the vicious man as tormented with mental dissatisfaction by the consciousness of his transgressions, they must first represent him as in the main basis of his character, at least in some degree, morally good; just as he who is pleased with the consciousness of right conduct must be conceived as already virtuous. The notion of morality and duty must, therefore, have preceded any regard to this satisfaction, and cannot be derived from it. A man must first appreciate the importance of what we call duty, the authority of the moral law, and the immediate dignity which the following of it gives to the person in his own eyes, in order to feel that satisfaction in the consciousness of his conformity to it and the bitter remorse that accompanies the consciousness of its transgression. It is, therefore, impossible to feel this satisfaction or dissatisfaction prior to the knowledge of obligation, or to make it the basis of the latter. A man must be at least half honest in order even to be able to form a conception of these feelings. I do not deny that as the human will is, by virtue of liberty, capable of being immediately determined by the moral law, so frequent practice in accordance with this principle of determination can, at least, produce subjectively a feeling of satisfaction; on the contrary, it is a duty to establish and to cultivate this, which alone deserves to be called properly the moral feeling; but the notion of duty cannot be derived from it, else we should have to suppose a feeling for the law as such, and thus make that an object of sensation which can only be thought by the reason; and this, if it is not to be a flat contradiction, would destroy all notion of duty and put in its place a mere mechanical play of refined inclinations sometimes contending with the coarser.

If now we compare our formal supreme principle of pure practical reason (that of autonomy of the will) with all previous material principles of morality, we can exhibit them all in a table in which all possible cases are exhausted, except the one formal principle; and thus we can show visibly that it is vain to look for any other principle than that now proposed. In fact all possible principles of determination of the will are either merely subjective, and therefore empirical, or are also objective and rational; and both are either external or internal.

Practical Material Principles of Determination taken as the Foundation of Morality, are:

Education Physical feeling
(Montaigne) (Epicurus)
The civil Moral feeling
Constitution (Hutcheson)

Perfection Will of God
(Wolf and the (Crusius and other
Stoics) theological Moralists)

Those of the upper table are all empirical and evidently incapable of furnishing the universal principle of morality; but those in the lower table are based on reason (for perfection as a quality of things, and the highest perfection conceived as substance, that is, God, can only be thought by means of rational concepts). But the former notion, namely, that of perfection, may either be taken in a theoretic signification, and then it means nothing but the completeness of each thing in its own kind (transcendental), or that of a thing merely as a thing (metaphysical); and with that we are not concerned here. But the notion of perfection in a practical sense is the fitness or sufficiency of a thing for all sorts of purposes. This perfection, as a quality of man and consequently internal, is nothing but talent and, what strengthens or completes this, skill. Supreme perfection conceived as substance, that is God, and consequently external (considered practically), is the sufficiency of this being for all ends. Ends then must first be given, relatively to which only can the notion of perfection (whether internal in ourselves or external in God) be the determining principle of the will. But an end- being an object which must precede the determination of the will by a practical rule and contain the ground of the possibility of this determination, and therefore contain also the matter of the will, taken as its determining principle- such an end is always empirical and, therefore, may serve for the Epicurean principle of the happiness theory, but not for the pure rational principle of morality and duty. Thus, talents and the improvement of them, because they contribute to the advantages of life; or the will of God, if agreement with it be taken as the object of the will, without any antecedent independent practical principle, can be motives only by reason of the happiness expected therefrom. Hence it follows, first, that all the principles here stated are material; secondly, that they include all possible material principles; and, finally, the conclusion, that since material principles are quite incapable of furnishing the supreme moral law (as has been shown), the formal practical principle the pure reason (according to which the mere form of a universal legislation must constitute the supreme and immediate determining principle of the will) is the only one possible which is adequate to furnish categorical imperatives, that is, practical laws (which make actions a duty), and in general to serve as the principle of morality, both in criticizing conduct and also in its application to the human will to determine it.

I. Of the Deduction of the Fundamental Principles of Pure Practical Reason

This Analytic shows that pure reason can be practical, that is, can of itself determine the will independently of anything empirical; and this it proves by a fact in which pure reason in us proves itself actually practical, namely, the autonomy shown in the fundamental principle of morality, by which reason determines the will to action.

It shows at the same time that this fact is inseparably connected with the consciousness of freedom of the will, nay, is identical with it; and by this the will of a rational being, although as belonging to the world of sense it recognizes itself as necessarily subject to the laws of causality like other efficient causes; yet, at the same time, on another side, namely, as a being in itself, is conscious of existing in and being determined by an intelligible order of things; conscious not by virtue of a special intuition of itself, but by virtue of certain dynamical laws which determine its causality in the sensible world; for it has been elsewhere proved that if freedom is predicated of us, it transports us into an intelligible order of things.

Now, if we compare with this the analytical part of the critique of pure speculative reason, we shall see a remarkable contrast. There it was not fundamental principles, but pure, sensible intuition (space and time), that was the first datum that made a priori knowledge possible, though only of objects of the senses. Synthetical principles could not be derived from mere concepts without intuition; on the contrary, they could only exist with reference to this intuition, and therefore to objects of possible experience, since it is the concepts of the understanding, united with this intuition, which alone make that knowledge possible which we call experience. Beyond objects of experience, and therefore with regard to things as noumena, all positive knowledge was rightly disclaimed for speculative reason. This reason, however, went so far as to establish with certainty the concept of noumena; that is, the possibility, nay, the necessity, of thinking them; for example, it showed against all objections that the supposition of freedom, negatively considered, was quite consistent with those principles and limitations of pure theoretic reason. But it could not give us any definite enlargement of our knowledge with respect to such objects, but, on the contrary, cut off all view of them altogether.

On the other hand, the moral law, although it gives no view, yet gives us a fact absolutely inexplicable from any data of the sensible world, and the whole compass of our theoretical use of reason, a fact which points to a pure world of the understanding, nay, even defines it positively and enables us to know something of it, namely, a law.

This law (as far as rational beings are concerned) gives to the world of sense, which is a sensible system of nature, the form of a world of the understanding, that is, of a supersensible system of nature, without interfering with its mechanism. Now, a system of nature, in the most general sense, is the existence of things under laws. The sensible nature of rational beings in general is their existence under laws empirically conditioned, which, from the point of view of reason, is heteronomy. The supersensible nature of the same beings, on the other hand, is their existence according to laws which are independent of every empirical condition and, therefore, belong to the autonomy of pure reason. And, since the laws by which the existence of things depends on cognition are practical, supersensible nature, so far as we can form any notion of it, is nothing else than a system of nature under the autonomy of pure practical reason. Now, the law of this autonomy is the moral law, which, therefore, is the fundamental law of a supersensible nature, and of a pure world of understanding, whose counterpart must exist in the world of sense, but without interfering with its laws. We might call the former the archetypal world (natura archetypa), which we only know in the reason; and the latter the ectypal world (natura ectypa), because it contains the possible effect of the idea of the former which is the determining principle of the will. For the moral law, in fact, transfers us ideally into a system in which pure reason, if it were accompanied with adequate physical power, would produce the summum bonum, and it determines our will to give the sensible world the form of a system of rational beings.

The least attention to oneself proves that this idea really serves as the model for the determinations of our will.

When the maxim which I am disposed to follow in giving testimony is tested by the practical reason, I always consider what it would be if it were to hold as a universal law of nature. It is manifest that in this view it would oblige everyone to speak the truth. For it cannot hold as a universal law of nature that statements should be allowed to have the force of proof and yet to be purposely untrue. Similarly, the maxim which I adopt with respect to disposing freely of my life is at once determined, when I ask myself what it should be, in order that a system, of which it is the law, should maintain itself. It is obvious that in such a system no one could arbitrarily put an end to his own life, for such an arrangement would not be a permanent order of things. And so in all similar cases. Now, in nature, as it actually is an object of experience, the free will is not of itself determined to maxims which could of themselves be the foundation of a natural system of universal laws, or which could even be adapted to a system so constituted; on the contrary, its maxims are private inclinations which constitute, indeed, a natural whole in conformity with pathological (physical) laws, but could not form part of a system of nature, which would only be possible through our will acting in accordance with pure practical laws. Yet we are, through reason, conscious of a law to which all our maxims are subject, as though a natural order must be originated from our will. This law, therefore, must be the idea of a natural system not given in experience, and yet possible through freedom; a system, therefore, which is supersensible, and to which we give objective reality, at least in a practical point of view, since we look on it as an object of our will as pure rational beings.

Hence the distinction between the laws of a natural system to which the will is subject, and of a natural system which is subject to a will (as far as its relation to its free actions is concerned), rests on this, that in the former the objects must be causes of the ideas which determine the will; whereas in the latter the will is the cause of the objects; so that its causality has its determining principle solely in the pure faculty of reason, which may therefore be called a pure practical reason.

There are therefore two very distinct problems: how, on the one side, pure reason can cognise objects a priori, and how on the other side it can be an immediate determining principle of the will, that is, of the causality of the rational being with respect to the reality of objects (through the mere thought of the universal validity of its own maxims as laws).

The former, which belongs to the critique of the pure speculative reason, requires a previous explanation, how intuitions without which no object can be given, and, therefore, none known synthetically, are possible a priori; and its solution turns out to be that these are all only sensible and, therefore, do not render possible any speculative knowledge which goes further than possible experience reaches; and that therefore all the principles of that pure speculative reason avail only to make experience possible; either experience of given objects or of those that may be given ad infinitum, but never are completely given.

The latter, which belongs to the critique of practical reason, requires no explanation how the objects of the faculty of desire are possible, for that being a problem of the theoretical knowledge of nature is left to the critique of the speculative reason, but only how reason can determine the maxims of the will; whether this takes place only by means of empirical ideas as principles of determination, or whether pure reason can be practical and be the law of a possible order of nature, which is not empirically knowable. The possibility of such a supersensible system of nature, the conception of which can also be the ground of its reality through our own free will, does not require any a priori intuition (of an intelligible world) which, being in this case supersensible, would be impossible for us. For the question is only as to the determining principle of volition in its maxims, namely, whether it is empirical, or is a conception of the pure reason (having the legal character belonging to it in general), and how it can be the latter. It is left to the theoretic principles of reason to decide whether the causality of the will suffices for the realization of the objects or not, this being an inquiry into the possibility of the objects of the volition. Intuition of these objects is therefore of no importance to the practical problem. We are here concerned only with the determination of the will and the determining principles of its maxims as a free will, not at all with the result. For, provided only that the will conforms to the law of pure reason, then let its power in execution be what it may, whether according to these maxims of legislation of a possible system of nature any such system really results or not, this is no concern of the critique, which only inquires whether, and in what way, pure reason can be practical, that is directly determine the will.

In this inquiry criticism may and must begin with pure practical laws and their reality. But instead of intuition it takes as their foundation the conception of their existence in the intelligible world, namely, the concept of freedom. For this concept has no other meaning, and these laws are only possible in relation to freedom of the will; but freedom being supposed, they are necessary; or conversely freedom is necessary because those laws are necessary, being practical postulates. It cannot be further explained how this consciousness of the moral law, or, what is the same thing, of freedom, is possible; but that it is admissible is well established in the theoretical critique.

The exposition of the supreme principle of practical reason is now finished; that is to say, it has been- shown first, what it contains, that it subsists for itself quite a priori and independent of empirical principles; and next in what it is distinguished from all other practical principles. With the deduction, that is, the justification of its objective and universal validity, and the discernment of the possibility of such a synthetical proposition a priori, we cannot expect to succeed so well as in the case of the principles of pure theoretical reason. For these referred to objects of possible experience, namely, to phenomena, and we could prove that these phenomena could be known as objects of experience only by being brought under the categories in accordance with these laws; and consequently that all possible experience must conform to these laws. But I could not proceed in this way with the deduction of the moral law. For this does not concern the knowledge of the properties of objects, which may be given to the reason from some other source; but a knowledge which can itself be the ground of the existence of the objects, and by which reason in a rational being has causality, i.e., pure reason, which can be regarded as a faculty immediately determining the will.

Now all our human insight is at an end as soon as we have arrived at fundamental powers or faculties, for the possibility of these cannot be understood by any means, and just as little should it be arbitrarily invented and assumed. Therefore, in the theoretic use of reason, it is experience alone that can justify us in assuming them. But this expedient of adducing empirical proofs, instead of a deduction from a priori sources of knowledge, is denied us here in respect to the pure practical faculty of reason. For whatever requires to draw the proof of its reality from experience must depend for the grounds of its possibility on principles of experience; and pure, yet practical, reason by its very notion cannot be regarded as such. Further, the moral law is given as a fact of pure reason of which we are a priori conscious, and which is apodeictically certain, though it be granted that in experience no example of its exact fulfilment can be found. Hence, the objective reality of the moral law cannot be proved by any deduction by any efforts of theoretical reason, whether speculative or empirically supported, and therefore, even if we renounced its apodeictic certainty, it could not be proved a posteriori by experience, and yet it is firmly established of itself.

But instead of this vainly sought deduction of the moral principle, something else is found which was quite unexpected, namely, that this moral principle serves conversely as the principle of the deduction of an inscrutable faculty which no experience could prove, but of which speculative reason was compelled at least to assume the possibility (in order to find amongst its cosmological ideas the unconditioned in the chain of causality, so as not to contradict itself)- I mean the faculty of freedom. The moral law, which itself does not require a justification, proves not merely the possibility of freedom, but that it really belongs to beings who recognize this law as binding on themselves. The moral law is in fact a law of the causality of free agents and, therefore, of the possibility of a supersensible system of nature, just as the metaphysical law of events in the world of sense was a law of causality of the sensible system of nature; and it therefore determines what speculative philosophy was compelled to leave undetermined, namely, the law for a causality, the concept of which in the latter was only negative; and therefore for the first time gives this concept objective reality.

This sort of credential of the moral law, viz., that it is set forth as a principle of the deduction of freedom, which is a causality of pure reason, is a sufficient substitute for all a priori justification, since theoretic reason was compelled to assume at least the possibility of freedom, in order to satisfy a want of its own. For the moral law proves its reality, so as even to satisfy the critique of the speculative reason, by the fact that it adds a positive definition to a causality previously conceived only negatively, the possibility of which was incomprehensible to speculative reason, which yet was compelled to suppose it. For it adds the notion of a reason that directly determines the will (by imposing on its maxims the condition of a universal legislative form); and thus it is able for the first time to give objective, though only practical, reality to reason, which always became transcendent when it sought to proceed speculatively with its ideas. It thus changes the transcendent use of reason into an immanent use (so that reason is itself, by means of ideas, an efficient cause in the field of experience).

The determination of the causality of beings in the world of sense, as such, can never be unconditioned; and yet for every series of conditions there must be something unconditioned, and therefore there must be a causality which is determined wholly by itself. Hence, the idea of freedom as a faculty of absolute spontaneity was not found to be a want but, as far as its possibility is concerned, an analytic principle of pure speculative reason. But as it is absolutely impossible to find in experience any example in accordance with this idea, because amongst the causes of things as phenomena it would be impossible to meet with any absolutely unconditioned determination of causality, we were only able to defend our supposition that a freely acting cause might be a being in the world of sense, in so far as it is considered in the other point of view as a noumenon, showing that there is no contradiction in regarding all its actions as subject to physical conditions so far as they are phenomena, and yet regarding its causality as physically unconditioned, in so far as the acting being belongs to the world of understanding, and in thus making the concept of freedom the regulative principle of reason. By this principle I do not indeed learn what the object is to which that sort of causality is attributed; but I remove the difficulty, for, on the one side, in the explanation of events in the world, and consequently also of the actions of rational beings, I leave to the mechanism of physical necessity the right of ascending from conditioned to condition ad infinitum, while on the other side I keep open for speculative reason the place which for it is vacant, namely, the intelligible, in order to transfer the unconditioned thither. But I was not able to verify this supposition; that is, to change it into the knowledge of a being so acting, not even into the knowledge of the possibility of such a being. This vacant place is now filled by pure practical reason with a definite law of causality in an intelligible world (causality with freedom), namely, the moral law. Speculative reason does not hereby gain anything as regards its insight, but only as regards the certainty of its problematical notion of freedom, which here obtains objective reality, which, though only practical, is nevertheless undoubted. Even the notion of causality- the application, and consequently the signification, of which holds properly only in relation to phenomena, so as to connect them into experiences (as is shown by the Critique of Pure Reason)- is not so enlarged as to extend its use beyond these limits. For if reason sought to do this, it would have to show how the logical relation of principle and consequence can be used synthetically in a different sort of intuition from the sensible; that is how a causa noumenon is possible. This it can never do; and, as practical reason, it does not even concern itself with it, since it only places the determining principle of causality of man as a sensible creature (which is given) in pure reason (which is therefore called practical); and therefore it employs the notion of cause, not in order to know objects, but to determine causality in relation to objects in general. It can abstract altogether from the application of this notion to objects with a view to theoretical knowledge (since this concept is always found a priori in the understanding even independently of any intuition). Reason, then, employs it only for a practical purpose, and hence we can transfer the determining principle of the will into the intelligible order of things, admitting, at the same time, that we cannot understand how the notion of cause can determine the knowledge of these things. But reason must cognise causality with respect to the actions of the will in the sensible world in a definite manner; otherwise, practical reason could not really produce any action. But as to the notion which it forms of its own causality as noumenon, it need not determine it theoretically with a view to the cognition of its supersensible existence, so as to give it significance in this way. For it acquires significance apart from this, though only for practical use, namely, through the moral law. Theoretically viewed, it remains always a pure a priori concept of the understanding, which can be applied to objects whether they have been given sensibly or not, although in the latter case it has no definite theoretical significance or application, but is only a formal, though essential, conception of the understanding relating to an object in general. The significance which reason gives it through the moral law is merely practical, inasmuch as the idea of the idea of the law of causality (of the will) has self causality, or is its determining principle.

II. Of the Right that Pure Reason in its Practical use has to an Extension which is not possible to it in its Speculative Use

We have in the moral principle set forth a law of causality, the determining principle of which is set above all the conditions of the sensible world; we have it conceived how the will, as belonging to the intelligible world, is determinable, and therefore we therefore we have its subject (man) not merely conceived as belonging to a world of pure understanding, and in this respect unknown (which the critique of speculative reason enabled us to do), but also defined as regards his causality by means of a law which cannot be reduced to any physical law of the sensible world; and therefore our knowledge is extended beyond the limits of that world, a pretension which the Critique of Pure Reason declared to be futile in all speculation. Now, how is the practical use of pure reason here to be reconciled with the theoretical, as to the determination of the limits of its faculty?

David Hume, of whom we may say that he commenced the assault on the claims of pure reason, which made a thorough investigation of it necessary, argued thus: The notion of cause is a notion that involves the necessity of the connexion of the existence of different things (and that, in so far as they are different), so that, given A, I know that something quite distinct there from, namely B, must necessarily also exist. Now necessity can be attributed to a connection, only in so far as it is known a priori, for experience would only enable us to know of such a connection that it exists, not that it necessarily exists. Now, it is impossible, says he, to know a priori and as necessary the connection between one thing and another (or between one attribute and another quite distinct) when they have not been given in experience. Therefore the notion of a cause is fictitious and delusive and, to speak in the mildest way, is an illusion, only excusable inasmuch as the custom (a subjective necessity) of perceiving certain things, or their attributes as often associated in existence along with or in succession to one another, is insensibly taken for an objective necessity of supposing such a connection in the objects themselves; and thus the notion of a cause has been acquired surreptitiously and not legitimately; nay, it can never be so acquired or authenticated, since it demands a connection in itself vain, chimerical, and untenable in presence of reason, and to which no object can ever correspond. In this way was empiricism first introduced as the sole source of principles, as far as all knowledge of the existence of things is concerned (mathematics therefore remaining excepted); and with empiricism the most thorough scepticism, even with regard to the whole science of nature( as philosophy). For on such principles we can never conclude from given attributes of things as existing to a consequence (for this would require the notion of cause, which involves the necessity of such a connection); we can only, guided by imagination, expect similar cases- an expectation which is never certain, however of ten it has been fulfilled. Of no event could we say: a certain thing must have preceded it, on which it necessarily followed; that is, it must have a cause; and therefore, however frequent the cases we have known in which there was such an antecedent, so that a rule could be derived from them, yet we never could suppose it as always and necessarily so happening; we should, therefore, be obliged to leave its share to blind chance, with which all use of reason comes to an end; and this firmly establishes scepticism in reference to arguments ascending from effects to causes and makes it impregnable.

Mathematics escaped well, so far, because Hume thought that its propositions were analytical; that is, proceeded from one property to another, by virtue of identity and, consequently, according to the principle of contradiction. This, however, is not the case, since, on the contrary, they are synthetical; and although geometry, for example, has not to do with the existence of things, but only with their a priori properties in a possible intuition, yet it proceeds just as in the case of the causal notion, from one property (A) to another wholly distinct (B), as necessarily connected with the former. Nevertheless, mathematical science, so highly vaunted for its apodeictic certainty, must at last fall under this empiricism for the same reason for which Hume put custom in the place of objective necessity in the notion of cause and, in spite of all its pride, must consent to lower its bold pretension of claiming assent a priori and depend for assent to the universality of its propositions on the kindness of observers, who, when called as witnesses, would surely not hesitate to admit that what the geometer propounds as a theorem they have always perceived to be the fact, and, consequently, although it be not necessarily true, yet they would permit us to expect it to be true in the future. In this manner Hume's empiricism leads inevitably to scepticism, even with regard to mathematics, and consequently in every scientific theoretical use of reason (for this belongs either to philosophy or mathematics). Whether with such a terrible overthrow of the chief branches of knowledge, common reason will escape better, and will not rather become irrecoverably involved in this destruction of all knowledge, so that from the same principles a universal scepticism should follow (affecting, indeed, only the learned), this I will leave everyone to judge for himself.

As regards my own labours in the critical examination of pure reason, which were occasioned by Hume's sceptical teaching, but went much further and embraced the whole field of pure theoretical reason in its synthetic use and, consequently, the field of what is called metaphysics in general; I proceeded in the following manner with respect to the doubts raised by the Scottish philosopher touching the notion of causality. If Hume took the objects of experience for things in themselves (as is almost always done), he was quite right in declaring the notion of cause to be a deception and false illusion; for as to things in themselves, and their attributes as such, it is impossible to see why because A is given, B, which is different, must necessarily be also given, and therefore he could by no means admit such an a priori knowledge of things in themselves. Still less could this acute writer allow an empirical origin of this concept, since this is directly contradictory to the necessity of connection which constitutes the essence of the notion of causality, hence the notion was proscribed, and in its place was put custom in the observation of the course of perceptions.

It resulted, however, from my inquiries, that the objects with which we have to do in experience are by no means things in themselves, but merely phenomena; and that although in the case of things in themselves it is impossible to see how, if A is supposed, it should be contradictory that B, which is quite different from A, should not also be supposed (i.e., to see the necessity of the connection between A as cause and B as effect); yet it can very well be conceived that, as phenomena, they may be necessarily connected in one experience in a certain way (e.g., with regard to time-relations); so that they could not be separated without contradicting that connection, by means of which this experience is possible in which they are objects and in which alone they are cognisable by us. And so it was found to be in fact; so that I was able not only to prove the objective reality of the concept of cause in regard to objects of experience, but also to deduce it as an a priori concept by reason of the necessity of the connection it implied; that is, to show the possibility of its origin from pure understanding without any empirical sources; and thus, after removing the source of empiricism, I was able also to overthrow the inevitable consequence of this, namely, scepticism, first with regard to physical science, and then with regard to mathematics (in which empiricism has just the same grounds), both being sciences which have reference to objects of possible experience; herewith overthrowing the thorough doubt of whatever theoretic reason professes to discern.

But how is it with the application of this category of causality (and all the others; for without them there can be no knowledge of anything existing) to things which are not objects of possible experience, but lie beyond its bounds? For I was able to deduce the objective reality of these concepts only with regard to objects of possible experience. But even this very fact, that I have saved them, only in case I have proved that objects may by means of them be thought, though not determined a priori; this it is that gives them a place in the pure understanding, by which they are referred to objects in general (sensible or not sensible). If anything is still wanting, it is that which is the condition of the application of these categories, and especially that of causality, to objects, namely, intuition; for where this is not given, the application with a view to theoretic knowledge of the object, as a noumenon, is impossible and, therefore, if anyone ventures on it, is (as in the Critique of Pure Reason) absolutely forbidden. Still, the objective reality of the concept (of causality) remains, and it can be used even of noumena, but without our being able in the least to define the concept theoretically so as to produce knowledge. For that this concept, even in reference to an object, contains nothing impossible, was shown by this, that, even while applied to objects of sense, its seat was certainly fixed in the pure understanding; and although, when referred to things in themselves (which cannot be objects of experience), it is not capable of being determined so as to represent a definite object for the purpose of theoretic knowledge; yet for any other purpose (for instance, a practical) it might be capable of being determined so as to have such application. This could not be the case if, as Hume maintained, this concept of causality contained something absolutely impossible to be thought.

In order now to discover this condition of the application of the said concept to noumena, we need only recall why we are not content with its application to objects of experience, but desire also to apply it to things in themselves. It will appear, then, that it is not a theoretic but a practical purpose that makes this a necessity. In speculation, even if we were successful in it, we should not really gain anything in the knowledge of nature, or generally with regard to such objects as are given, but we should make a wide step from the sensibly conditioned (in which we have already enough to do to maintain ourselves, and to follow carefully the chain of causes) to the supersensible, in order to complete our knowledge of principles and to fix its limits; whereas there always remains an infinite chasm unfilled between those limits and what we know; and we should have hearkened to a vain curiosity rather than a solid-desire of knowledge.

But, besides the relation in which the understanding stands to objects (in theoretical knowledge), it has also a relation to the faculty of desire, which is therefore called the will, and the pure will, inasmuch as pure understanding (in this case called reason) is practical through the mere conception of a law. The objective reality of a pure will, or, what is the same thing, of a pure practical reason, is given in the moral law a priori, as it were, by a fact, for so we may name a determination of the will which is inevitable, although it does not rest on empirical principles. Now, in the notion of a will the notion of causality is already contained, and hence the notion of a pure will contains that of a causality accompanied with freedom, that is, one which is not determinable by physical laws, and consequently is not capable of any empirical intuition in proof of its reality, but, nevertheless, completely justifies its objective reality a priori in the pure practical law; not, indeed (as is easily seen) for the purposes of the theoretical, but of the practical use of reason. Now the notion of a being that has free will is the notion of a causa noumenon, and that this notion involves no contradiction, we are already assured by the fact- that inasmuch as the concept of cause has arisen wholly from pure understanding, and has its objective reality assured by the deduction, as it is moreover in its origin independent of any sensible conditions, it is, therefore, not restricted to phenomena (unless we wanted to make a definite theoretic use of it), but can be applied equally to things that are objects of the pure understanding. But, since this application cannot rest on any intuition (for intuition can only be sensible), therefore, causa noumenon, as regards the theoretic use of reason, although a possible and thinkable, is yet an empty notion. Now, I do not desire by means of this to understand theoretically the nature of a being, in so far as it has a pure will; it is enough for me to have thereby designated it as such, and hence to combine the notion of causality with that of freedom (and what is inseparable from it, the moral law, as its determining principle). Now, this right I certainly have by virtue of the pure, not-empirical origin of the notion of cause, since I do not consider myself entitled to make any use of it except in reference to the moral law which determines its reality, that is, only a practical use.

If, with Hume, I had denied to the notion of causality all objective reality in its [theoretic] use, not merely with regard to things in themselves (the supersensible), but also with regard to the objects of the senses, it would have lost all significance, and being a theoretically impossible notion would have been declared to be quite useless; and since what is nothing cannot be made any use of, the practical use of a concept theoretically null would have been absurd. But, as it is, the concept of a causality free from empirical conditions, although empty, i.e., without any appropriate intuition), is yet theoretically possible, and refers to an indeterminate object; but in compensation significance is given to it in the moral law and consequently in a practical sense. I have, indeed, no intuition which should determine its objective theoretic reality, but not the less it has a real application, which is exhibited in concreto in intentions or maxims; that is, it has a practical reality which can be specified, and this is sufficient to justify it even with a view to noumena.

Now, this objective reality of a pure concept of the understanding in the sphere of the supersensible, once brought in, gives an objective reality also to all the other categories, although only so far as they stand in necessary connexion with the determining principle of the will (the moral law); a reality only of practical application, which has not the least effect in enlarging our theoretical knowledge of these objects, or the discernment of their nature by pure reason. So we shall find also in the sequel that these categories refer only to beings as intelligences, and in them only to the relation of reason to the will; consequently, always only to the practical, and beyond this cannot pretend to any knowledge of these beings; and whatever other properties belonging to the theoretical representation of supersensible things may be brought into connexion with these categories, this is not to be reckoned as knowledge, but only as a right (in a practical point of view, however, it is a necessity) to admit and assume such beings, even in the case where we [conceive] supersensible beings (e.g., God) according to analogy, that is, a purely rational relation, of which we make a practical use with reference to what is sensible; and thus the application to the supersensible solely in a practical point of view does not give pure theoretic reason the least encouragement to run riot into the transcendent.

CHAPTER II. Of the Concept of an Object of Pure Practical Reason

By a concept of the practical reason I understand the idea of an object as an effect possible to be produced through freedom. To be an object of practical knowledge, as such, signifies, therefore, only the relation of the will to the action by which the object or its opposite would be realized; and to decide whether something is an object of pure practical reason or not is only to discern the possibility or impossibility of willing the action by which, if we had the required power (about which experience must decide), a certain object would be realized. If the object be taken as the determining principle of our desire, it must first be known whether it is physically possible by the free use of our powers, before we decide whether it is an object of practical reason or not. On the other hand, if the law can be considered a priori as the determining principle of the action, and the latter therefore as determined by pure practical reason, the judgement whether a thing is an object of pure practical reason or not does not depend at all on the comparison with our physical power; and the question is only whether we should will an action that is directed to the existence of an object, if the object were in our power; hence the previous question is only as the moral possibility of the action, for in this case it is not the object, but the law of the will, that is the determining principle of the action. The only objects of practical reason are therefore those of good and evil. For by the former is meant an object necessarily desired according to a principle of reason; by the latter one necessarily shunned, also according to a principle of reason.

If the notion of good is not to be derived from an antecedent practical law, but, on the contrary, is to serve as its foundation, it can only be the notion of something whose existence promises pleasure, and thus determines the causality of the subject to produce it, that is to say, determines the faculty of desire. Now, since it is impossible to discern a priori what idea will be accompanied with pleasure and what with pain, it will depend on experience alone to find out what is primarily good or evil. The property of the subject, with reference to which alone this experiment can be made, is the feeling of pleasure and pain, a receptivity belonging to the internal sense; thus that only would be primarily good with which the sensation of pleasure is immediately connected, and that simply evil which immediately excites pain. Since, however, this is opposed even to the usage of language, which distinguishes the pleasant from the good, the unpleasant from the evil, and requires that good and evil shall always be judged by reason, and, therefore, by concepts which can be communicated to everyone, and not by mere sensation, which is limited to individual [subjects] and their susceptibility; and, since nevertheless, pleasure or pain cannot be connected with any idea of an object a priori, the philosopher who thought himself obliged to make a feeling of pleasure the foundation of his practical judgements would call that good which is a means to the pleasant, and evil, what is a cause of unpleasantness and pain; for the judgement on the relation of means to ends certainly belongs to reason. But, although reason is alone capable of discerning the connexion of means with their ends (so that the will might even be defined as the faculty of ends, since these are always determining principles of the desires), yet the practical maxims which would follow from the aforesaid principle of the good being merely a means, would never contain as the object of the will anything good in itself, but only something good for something; the good would always be merely the useful, and that for which it is useful must always lie outside the will, in sensation. Now if this as a pleasant sensation were to be distinguished from the notion of good, then there would be nothing primarily good at all, but the good would have to be sought only in the means to something else, namely, some pleasantness.