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.

Practical principles are statements that generally determine the will and include several practical rules. They are subjective, or maxims, when a person regards their condition as valid only for their own will. But they are objective, or practical laws, when the condition is recognized as valid for every rational being’s will.

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.

Suppose that pure reason contains a practical motive of its own, one sufficient to determine the will. Then there are practical laws. Otherwise, all practical principles will be mere maxims. If a rational being’s will is affected by feelings and desires, its maxims may conflict with practical laws it recognizes. For example, someone may make it his maxim never to leave an injury unavenged. Yet he may see that this is not a practical law, but only his own maxim. On the contrary, the maxim would contradict itself if taken as a rule for the will of every rational being. In natural philosophy, principles describing what happens are also laws of nature. One example is the principle that action and reaction are equal in the transfer of motion. These principles are laws because reason is used theoretically and is guided by the nature of the object. Practical philosophy, by contrast, deals only with what determines the will. Here, the principles people make for themselves are not laws that necessarily bind them. In practical matters, reason deals with the subject, namely, with its capacity for desire. Differences in that capacity may produce different rules. A practical rule is always a product of reason because it prescribes action as a means to an effect. But for a being whose will is not determined by reason alone, the rule is an imperative. An imperative is a rule expressed as a "shall." It states that the action is objectively necessary. It means that, if reason completely determined the will, the action would necessarily follow the rule. Imperatives are therefore objectively valid. They are quite distinct from maxims, which are subjective principles. Imperatives may determine the conditions under which a rational being can act as a cause. In that case, they refer only to an effect and the means of achieving it. Or they may determine the will alone, whether or not the will is capable of producing the effect. The first kind would be hypothetical imperatives, containing only instructions about how to achieve an end. The second kind, by contrast, would be categorical, and only they would be practical laws. Maxims, then, are principles, but not imperatives. Imperatives themselves are practical precepts rather than laws when they are conditional. These are hypothetical imperatives, which determine the will only in relation to a desired effect, not simply as a will. Laws must be sufficient to determine the will as a will. They must do so even before I ask whether I have enough power or the necessary means to produce a desired effect. Laws are therefore categorical. Otherwise, they are not laws at all, because they lack necessity. To be practical, this necessity must be independent of conditions arising from feelings and desires. Such conditions are only contingently connected with the will. For example, tell a man that he must be industrious and thrifty in his youth so that he will not be in need in old age. This is a correct and important practical precept for the will. But clearly, his will is directed here toward something else that he is presumed to desire. As for that desire, we must leave it to him to decide whether he expects other resources besides what he earns. He may also expect not to grow old, or think he could manage with little if he were in need later. Reason alone can produce a rule involving necessity, and it does give this precept necessity. Otherwise, the precept would not be an imperative. But this necessity depends on subjective conditions, and cannot be assumed to hold equally for everyone. For reason to give laws, however, it must need to presuppose only itself. Rules are objectively and universally valid only when they hold without contingent subjective conditions that distinguish one rational being from another. Now tell a man that he should never make a deceitful promise. This rule concerns only his will, whether or not he can achieve his purposes by following it. The rule is to determine his act of willing alone, independently of experience. If the rule is found to be practically right, then it is a law, because it is a categorical imperative. Practical laws therefore concern the will alone, without regard to what its action achieves. We may disregard what it achieves, since that belongs to the world of sense, in order to have practical laws in their purity.

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.

All practical principles that assume an object of desire as the basis for determining the will are empirical. They cannot provide 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.

By the matter of the faculty of desire, I mean an object whose realization is desired. Now, suppose the desire for this object comes before the practical rule and is the condition for making the rule a principle. In that case, I say, first, that the principle is wholly empirical. For what determines the choice is the idea of an object and its relation to the subject. Through this relation, the idea determines the subject’s faculty of desire to realize the object. Such a relation to the subject is called pleasure in the realization of an object. This pleasure must therefore be assumed as a condition for the determination of the will. But it is impossible to know a priori whether the idea of an object will be connected with pleasure, pain, or neither. In such cases, the principle that determines the choice must therefore be empirical. So, too, must the material practical principle that assumes 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.

Second, we can know whether someone is susceptible to pleasure or pain only through experience. Not all rational beings can have this susceptibility to the same degree. A principle based on this subjective condition may serve as a maxim for someone who has this susceptibility. But it cannot serve as a law, even for that person. This is because the principle lacks the objective necessity that must be recognized a priori. Therefore, such a principle can never provide 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.

All material practical principles are of the same kind. They all fall under the general principle of self-love or personal 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.

Pleasure can arise from the idea of the idea of a thing’s existence. When this pleasure is meant to determine our desire for the thing, it depends on our capacity to be affected. This is because the pleasure depends on the presence of an object. It therefore belongs to the senses, or feeling, rather than to understanding. Understanding expresses how an idea relates to an object through concepts. It does not express how an idea relates to the subject through feelings. The pleasure is therefore practical only when the capacity for desire is determined by the pleasant feeling the subject expects from the object’s actual existence. Happiness is a rational being’s awareness of life’s pleasantness continuing without interruption throughout their existence. The principle of self-love makes this happiness the highest determining ground of the will. All material principles locate the determining ground of the will in pleasure or pain received from an object’s existence. They are therefore all of the same kind, since 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.

All material practical rules base the will’s decisions on lower desires. If no purely formal laws of the will were sufficient to determine it, we could not recognize 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.

It is surprising that otherwise perceptive people think they can distinguish higher desires from lower ones by their source. They think desires are higher or lower depending on whether the ideas associated with pleasure come from the senses or the understanding. But when we ask what determines desire, and find the answer in some expected pleasure, the source of the idea does not matter. What matters is only how much the object pleases us. An idea may or may not have its source in the understanding. But if it can determine our choice only by assuming that we feel pleasure, its power depends entirely on our inner sense. It depends on whether our inner sense can be pleasantly affected by the idea. Ideas of objects may be very different. They may come from the understanding or even from reason, rather than from the senses. Yet the feeling of pleasure through which they determine the will is always of the same kind. This feeling is the satisfaction we expect, which drives us to act to produce the object. Pleasure is always of the same kind, first, because we can know it only through experience. It is also of the same kind because it affects the same vital force, which shows itself in our capacity for desire. In this respect, one ground for determining the will can differ from another only in degree. Otherwise, how could we compare the strength of two grounds based on ideas from different faculties? How could we prefer the one that affects our capacity for desire most strongly? The same man may return an instructive book unread, though he cannot get it again, so that he does not miss a hunt. He may leave a fine speech halfway through, so that he is not late for dinner. He may leave a rational conversation, which he would otherwise value highly, to take his place at the gaming table. He may even turn away a poor man he would at other times enjoy helping. He may do this because he has just enough money in his pocket for admission to the theater. If his will is determined by the pleasure or displeasure he expects from any source, the kind of ideas that affect him makes no difference. To decide what to choose, he cares only about how great and lasting the pleasure is, how easily he can obtain it, and how often it can be repeated. A man who wants money to spend does not care whether the gold was dug from a mountain or washed out of sand. He cares only that it is accepted everywhere at the same value. In the same way, a man who cares only about enjoying life does not ask whether his ideas come from the understanding or the senses. He asks only how much pleasure they will give him and how great that pleasure will be over the longest time. Some people would gladly deny that pure reason can determine the will without assuming a feeling. Only such people could stray so far from their own account. They describe things as completely different in kind, although they themselves have already brought them under one and the same principle. For example, we observe that we can take pleasure in simply exercising power. We can enjoy being aware of our strength of mind when we overcome obstacles to our plans. We can also enjoy developing our mental talents, and so on. We rightly call these pleasures and enjoyments more refined, because they are more within our control than others. They do not wear out. Instead, they increase our capacity for further enjoyment of them. And while they delight us, they also develop us. But some claim that these pleasures therefore determine the will differently, and not through the senses. Yet the possibility of such pleasure assumes that we have an inborn feeling for it. That feeling is the first condition of our satisfaction. Their claim is like the thinking of ignorant people who enjoy dabbling in metaphysics. They imagine matter so subtle, so extraordinarily subtle, that they almost make themselves dizzy. Then they think they have conceived of a being that is both spiritual and extended in space. If, like Epicurus, we make virtue determine the will only through the pleasure it promises, we cannot then blame him for his conclusion. He holds that this pleasure is of the same kind as the pleasures of the coarsest senses. We have no reason at all to accuse him of holding that the ideas which arouse this feeling come only from the bodily senses. As far as we can tell, he looked for the source of many of these ideas in the use of our higher power of knowledge. But that did not, and could not, prevent him from holding that the pleasure itself is of the same kind. Given the principle stated above, intellectual ideas can determine the will only through the pleasure they give us. Consistency is a philosopher's highest obligation, yet it is the quality most rarely found. The ancient Greek schools give us more examples of consistency than we find in our syncretistic age. In our age, people devise a shallow and dishonest system that compromises between contradictory principles. They do this because it appeals more to a public content to know something about everything and nothing thoroughly, and so pleases 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.

The principle of personal happiness can determine the will only through the lower desires, however much understanding and reason it employs. So either there are no higher desires at all, or pure reason must be practical on its own. In other words, pure reason must be able to determine the will through the mere form of a practical rule. It must do so without assuming any feeling and therefore without any idea of what is pleasant or unpleasant. Such ideas are the content of desire and are always an empirical condition of its principles. Only when reason itself determines the will, rather than serving inclination, is there truly a higher desire. Desire determined by feeling is subordinate to this higher desire. The higher desire is genuinely and specifically distinct from desire determined by feeling. Even the slightest addition of motives based on feeling weakens its strength and superiority. In the same way, the slightest empirical condition would diminish and destroy the force and value of a mathematical proof. Through its practical law, reason determines the will directly, not through any intervening feeling of pleasure or pain. It does not even act through pleasure in the law itself. Only because pure reason can be practical can it also give laws.

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.

Every finite rational being necessarily wishes to be happy. This wish therefore inevitably helps determine what it desires. For we do not begin with satisfaction with our entire existence. Such bliss would imply an awareness of our own independent self-sufficiency. Instead, our finite nature sets us the problem of attaining satisfaction because we have wants. These wants concern the content of our desires. This content is relative to a subjective feeling of pleasure or pain. That feeling determines what we need to be satisfied with our condition. But the subject can know this material basis for determining desire only through experience. For this very reason, the problem of attaining satisfaction cannot be regarded as a law. A law is objective and must contain the same basis for determining the will in every case and for every rational being. The idea of happiness always underlies the practical relation between objects and our desires. But happiness is only a general name for the subjective principles that determine those desires. It determines nothing specific. Yet in this practical problem, we are concerned only with what specifically determines desire. The problem cannot be solved at all without that specific determination. Each person’s own feeling of pleasure and pain decides where that person finds happiness. Even in the same person, this will vary with different wants as the feeling changes. Thus, a law that is subjectively necessary, as a law of nature, is objectively a highly contingent practical principle. It can and must be very different in different people, so it can never provide a law. For in the desire for happiness, what matters is not the form of conformity to law. What matters is simply the content: whether I can expect pleasure from following the law, and how much. Principles of self-love may indeed contain universal rules of skill, telling us how to find means to accomplish our purpose. But in that case they are merely theoretical principles. * For example, they may tell someone who wants to eat bread how to build a mill. But practical rules based on such principles can never be universal. For the principle that determines desire is based on the feeling of pleasure and pain. That feeling can never be assumed to be directed toward the same objects in everyone.

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.

Suppose that all finite rational beings agreed completely about what gave them pleasure and pain. Suppose they also agreed about the means needed to gain pleasure and avoid pain. Even then, they could not establish the principle of self-love as a practical law. Their agreement itself would still be contingent. The principle determining their actions would still be valid only subjectively and based merely on experience. It would not have the necessity that belongs to every law: an objective necessity arising from a priori grounds. The only exception would be if we took this necessity to be merely physical, not practical at all. In that case, our inclinations would determine our actions as inevitably as seeing others yawn makes us yawn. It would be better to say that there are no practical laws, but only advice on satisfying our desires. That would be better than elevating merely subjective principles to the status of practical laws. Practical laws have objective necessity, not merely subjective necessity. They must be known by reason a priori, not through experience, however universal the experience may be. Even rules governing corresponding phenomena are called laws of nature only under certain conditions. We must either know them a priori, as with the laws of mechanics. Or we must suppose that we would know them a priori from objective grounds if our insight went further, as with chemical laws. But merely subjective practical principles are expressly required to rest on subjective conditions of choice, not objective ones. They must therefore always be regarded as mere maxims, never as practical laws. This second remark may at first seem to be a mere verbal refinement. But it defines the terms of the most important distinction that can arise 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.

A rational being can regard their maxims as universal practical laws only if they understand them as principles that determine the will by their form alone, not by their content.

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.

By the matter of a practical principle, I mean the object of the will. This object either determines the will or it does not. If the object determines the will, the rule of the will depends on an empirical condition. This condition is the relation between the idea that determines the will and the feeling of pleasure or pain. The rule therefore cannot be a practical law. Now, suppose we set aside all matter from a law, meaning every object that determines the will. Nothing remains but the form of universal legislation itself. Therefore, a rational being either cannot think of subjective practical principles, or maxims, as universal laws, or must suppose that their form alone makes them practical laws. This form is what makes the maxims fit to serve as universal 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.

Even the most ordinary understanding can tell, without instruction, which kinds of maxims are suitable for universal laws and which are not. Suppose, for example, that I make it my maxim to increase my wealth by every safe means. Now suppose someone has entrusted me with a deposit and has died without leaving any written record of it. This is just the kind of case my maxim applies to. I want to know whether my maxim can also hold as a universal practical law. So I apply it to this case and ask whether it could take the form of a law. Could I, through my maxim, also establish a law allowing everyone to deny holding a deposit that no one can prove exists? I immediately see that, as a law, this principle would destroy itself, because there would be no deposits. A practical law that I recognize as such must be suitable for universal legislation. This is a statement of identity and therefore self-evident. Now, if I say that my will is subject to a practical law, I cannot offer my inclination as a determining principle suitable for a universal practical law. In this case, that inclination is my greed. It is so far from being suitable for universal legislation that, if made into 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.

It is surprising, then, that intelligent people could have called the desire for happiness a universal practical law simply because everyone has that desire. On the same grounds, they also called the maxim by which everyone lets this desire determine their will a universal practical law. In other cases, a universal law of nature brings everything into harmony. Here, however, if we give the maxim the universality of a law, the very opposite of harmony follows. There would be the greatest conflict and the complete destruction of the maxim itself and its purpose. For then everyone’s will would not have one and the same object. Each person would have a separate object, their own private welfare. This may happen to agree with the equally selfish aims of others, but that is far from enough to make it a law. The occasional exceptions one is permitted to make are endless and cannot be fully captured in a single universal rule. The resulting harmony is like the harmony a satirical poem describes between a married couple bent on ruining each other: "O, marvellous harmony, what he wishes, she wishes also". Or it is like the pledge Francis I made to Emperor Charles V: "What my brother Charles wishes that I wish also" (namely, Milan). Principles based on experience cannot serve as the basis for any universal external legislation. They are equally unfit for internal legislation. For each person bases their inclination on their own self. And in the same person, sometimes one inclination is stronger, sometimes another. Under these conditions, it is quite impossible to find a law that governs all these inclinations by bringing them into harmony.

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.

Suppose that the mere lawgiving form of maxims is enough by itself to determine a will. What is the nature of a will that this form alone can determine?

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.

Only reason can conceive the bare form of the law. It is therefore not an object of the senses and does not belong to the class of phenomena. The idea of this form, when it determines the will, is therefore distinct from all the principles that determine events in nature according to the law of causality. In nature, the determining principles must themselves be phenomena. Now, suppose that nothing but this universal legislative form can serve as a law for the will. Then such a will must be understood as completely independent of the natural law governing how phenomena relate to one another, namely, the law of causality. This independence is called freedom in the strictest sense, that is, in the transcendental sense. Consequently, a will that can have no law but the mere legislative form of its maxim is a free will.

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

Assuming that a will is free, find the only law that can necessarily determine it.

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.

The matter of a practical law, that is, the object of a maxim, can only be given through experience. A free will is independent of empirical conditions, meaning conditions belonging to the world of sense. Yet it can still be determined. Therefore, a free will must find what determines it in the law, independently of the law’s matter. But apart from its matter, the law contains nothing except its legislative form. So only the legislative form contained in a maxim can determine 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.

Freedom and an unconditional practical law therefore imply each other. I do not ask here whether they are in fact distinct. Nor do I ask whether an unconditional law is merely the consciousness of pure practical reason, which is itself identical with the positive concept of freedom. I ask only where our knowledge of what is unconditionally practical begins. Does it begin with freedom or with the practical law? It cannot begin with freedom. We cannot be directly conscious of freedom, because our first concept of freedom is negative. Nor can we infer freedom from experience. Experience gives us knowledge only of the laws of appearances, and thus of the mechanism of nature, the direct opposite of freedom. It is therefore the moral law that first presents itself to us. We become directly conscious of it as soon as we form maxims for our will. The moral law leads us directly to the concept of freedom. For reason presents the moral law as a principle that determines the will, cannot be outweighed by any conditions of the senses, and is wholly independent of them. But how is consciousness of the moral law possible? We can become conscious of pure practical laws just as we become conscious of pure theoretical principles. We do so by attending to the necessity with which reason prescribes them and excludes all conditions drawn from experience. The concept of a pure will arises from the pure practical laws, just as the concept of a pure understanding arises from the pure theoretical principles. The following shows that our concepts stand in this order. It shows that morality first reveals freedom to us. It also shows that practical reason, through the concept of freedom, first presents theoretical reason with its most insoluble problem and leaves it deeply perplexed. Nothing in appearances can be explained by the concept of freedom. The mechanism of nature must provide the only guide to explaining them. Moreover, when pure reason tries to trace the series of causes back to the unconditioned, it falls into an antinomy, entangled in what cannot be understood on either side. Yet the mechanism of nature is at least useful for explaining appearances. So no one would ever have been rash enough to introduce freedom into science if the moral law, and with it practical reason, had not forced this idea on us. Experience, however, confirms that these ideas arise in this order. Suppose someone claims that his sexual desire is quite irresistible when the person he desires and the opportunity are present. Ask him whether he could control his passion if a gallows stood outside the house where he had this opportunity, so that he would be hanged immediately after satisfying his desire. We need not wonder long what he would answer. But suppose his ruler ordered him, on pain of the same immediate execution, to give false testimony against an honorable man. The ruler wants to destroy the man under a plausible pretext. Ask him whether he would consider it possible to overcome his love of life in that case, however great that love may be. He might not venture to say whether he would do so, but he must admit without hesitation that he could. He judges, then, that he can do something because he is conscious that he ought to do it. He recognizes that he is free, a fact he would never have known without the moral law.

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

Act so that the rule guiding your choices could always also serve as a universal law.

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 geometry has postulates that are practical propositions. But these postulates assume only that we can do something if we are required to do it. They are the only geometrical propositions that concern actual existence. They are therefore practical rules that apply only if the will has a particular aim. But the rule here says that we absolutely must act in a certain way. The practical rule is therefore unconditional. It is thus conceived a priori as a categorically practical proposition. It objectively determines the will, absolutely and immediately, through the practical rule itself. In this case, the rule is therefore a law, for pure reason, practical in itself, directly gives the law. The will is thought of as independent of empirical conditions. It is therefore a pure will, determined by the mere form of the law. This determining principle is regarded as the supreme condition of all maxims. This is strange enough and has no parallel in all the rest of our practical knowledge. The a priori thought of a possible universal legislation is merely a possibility. Yet it is commanded unconditionally as a law, without borrowing anything from experience or from any external will. This law, however, is not a command to do something to achieve a desired effect. If it were, the will would depend on physical conditions. Instead, it is a rule that determines the will a priori only with respect to the form of its maxims. The law applies only to the subjective form of principles. Yet it is at least not impossible to conceive that it determines the will through the objective form of law in general. We may call our consciousness of this fundamental law a fact of reason. We cannot derive it by reasoning from prior data of reason, such as the consciousness of freedom. For that consciousness is not given beforehand. Instead, the law forces itself on us as a synthetic a priori proposition. It is not based on any intuition, either pure or empirical. The proposition would indeed be analytic if freedom of the will were presupposed. But to presuppose freedom as a positive concept would require an intellectual intuition, and we cannot assume one here. Still, when we regard this law as given, we must take care not to misunderstand it. It is not an empirical fact, but the sole fact of pure reason. Through this fact, pure reason 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.

Pure reason is practical on its own. It gives us a universal law that 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 self-constrained, 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 differences, 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 fact just mentioned cannot be denied. We need only examine how people judge whether their actions are lawful. We then find that reason always compares the maxim of the will in any action with the pure will. It does so regardless of what inclination may say against it. Reason is incorruptible and constrains itself. In comparing the maxim with the pure will, reason compares it with itself, considered as practical a priori. This principle of morality is the supreme formal principle determining the will. It holds that position because its legislation is universal and takes no account of subjective differences. For the same reason, reason declares it a law for all rational beings insofar as they have a will. A will is the power to determine one’s causality through the conception of rules. The law therefore applies to rational beings insofar as they can act according to principles. This includes practical a priori principles, since only these have the necessity that reason requires in a principle. The law is therefore not limited to human beings. It applies to all finite beings who have reason and a will. It even includes the Infinite Being, as the supreme intelligence. For finite rational beings, however, the law takes the form of an imperative. As rational beings, they can be assumed to have a pure will. But they are also creatures affected by needs and physical motives. So they cannot be assumed to have a holy will, incapable of adopting any maxim that conflicts with the moral law. For them, then, the moral law is an imperative that commands categorically, because the law is unconditional. Such a will depends on the moral law through what we call obligation. Obligation involves a constraint to act, though this constraint comes only from reason and its objective law. The action is called duty because a will capable of choice is subject to pathological affections. It is not determined by them, however, and therefore remains free. Such a will involves wishes that arise from subjective causes. These wishes may often conflict with the pure objective principle that determines the will. The will therefore needs moral constraint, through practical reason’s resistance to those wishes. This may be called an internal but intellectual compulsion. In the supreme intelligence, the will capable of choice is rightly understood as incapable of adopting any maxim that could not also be an objective law. For that reason, holiness belongs to the supreme intelligence. This holiness does not place it above all practical laws. It places it above all practically restrictive laws, and therefore above obligation and duty. This holiness of will is, however, a practical idea. It must serve as a model that finite rational beings can approach only through endless progress. The pure moral law constantly and rightly holds this model before them. For this reason, the moral law itself is called holy. The most that finite practical reason can achieve is certainty that one’s maxims are progressing endlessly toward this model and are steadily disposed to advance. This is virtue. Virtue, at least as a naturally acquired capacity, can never be perfect. Assurance in this case never becomes apodeictic certainty. When it amounts only to persuasion, it 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.

The autonomy of the will is the sole principle behind all moral laws and all duties that conform to them. By contrast, heteronomy of the will cannot be the basis of any obligation. On the contrary, it opposes both the principle of obligation and 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.

In fact, morality has only one principle. It requires independence from all matter of the law, meaning any desired object. It also requires that the will be determined solely by the universal form of lawgiving that its maxim must be capable of taking. This independence is freedom in the negative sense. The self-legislation of pure reason, which is therefore practical reason, is freedom in the positive sense. Thus, the moral law expresses nothing other than the autonomy of pure practical reason, that is, freedom. Freedom is itself the formal condition of all maxims. Only on this condition can maxims agree with the supreme practical law. Suppose, then, that the matter of willing enters into the practical law as a condition of its possibility. This matter can only be the object of a desire connected with the law. The result is heteronomy of the will. In other words, the will depends on the physical law that we should follow some impulse or inclination. In that case, the will does not give itself the law. It gives itself only a rule for following pathological law rationally. In such a case, the maxim never contains the universal form of lawgiving. It not only creates no obligation but also opposes the principle of pure practical reason and therefore the moral disposition. This remains true even though the resulting action may conform 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.

A practical precept that depends on a material condition, and therefore on experience, must never be considered a practical law. The law of the pure will, which is free, places the will in a sphere entirely different from that of experience. The necessity involved in this law is not a physical necessity. It can therefore consist only in the formal conditions that make a law possible in general. All the material content of practical rules depends on subjective conditions. These conditions give the rules only a conditional universality: if I desire this or that, what must I do to obtain it? All such rules turn on the principle of personal happiness. It is certainly undeniable that every act of willing must have an object and therefore a material content. But it does not follow that this content determines the maxim and serves as its condition. If it did, the maxim could not be expressed in the form of a universal law. For then the expectation that the object would exist would determine the choice. The act of willing would have to assume that the capacity for desire depends on the existence of something. But this dependence can only be found in conditions of experience. It can therefore never provide a foundation for a necessary and universal rule. For example, the happiness of others may be the object of a rational being's will. But suppose it were the principle that determines the maxim. We would then have to assume that we find not only rational satisfaction in the welfare of others, but also a need for it, such as a sympathetic disposition creates in some people. But I cannot assume that every rational being has this need, and I cannot assume it of God at all. The material content may remain part of the maxim, but it must not be the maxim's condition. Otherwise, the maxim could not be fit to serve as a law. The mere form of law limits the material content. It must therefore also be a reason for including that content in the will, rather than assuming it in advance. For example, let the material content be my own happiness. I may attribute this rule to everyone, as I in fact may in the case of every finite being. But it can become an objective practical law only if I include the happiness of others. The law that we should promote the happiness of others does not therefore arise from assuming that everyone chooses their happiness as an object. Rather, it arises solely because the principle that determines the will is the form of universality. Reason requires this form as the condition for giving a maxim of self-love the objective validity of a law. So it was not the object, the happiness of others, that determined the pure will. It was only the form of law. By means of this form, I limited my maxim, which was based on inclination, so as to give it the universality of a law and make it fit for practical reason. This limitation alone, not the addition of an external motive, can give rise to the idea that I am obligated to extend my maxim of 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.

The principle of morality is directly opposed by making personal happiness the guiding principle of the will. As I showed above, this includes anything that bases the principle meant to serve as a law on something other than the legislative form of the maxim. This conflict is not merely logical. A logical conflict would arise if empirically conditioned rules were elevated to necessary principles of knowledge. The conflict over morality, however, is practical. It would destroy morality altogether if the voice of reason concerning the will were not so clear and irrepressible, and so distinctly audible even to ordinary people. The principle of personal happiness can be upheld only in the perplexing speculations of academic schools. These schools are bold enough to shut their ears to that heavenly voice in order to support a theory that requires no effort.

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.

Suppose an acquaintance you otherwise liked tried to justify lying under oath. First, he claimed that he had what he considered a sacred duty to look after his own happiness. Then he listed the advantages he had gained by lying. He also pointed out how carefully he had protected himself from being found out, even by you. He now reveals the secret to you only so that he can deny it at any time. Suppose he then seriously claimed that he had fulfilled a true human duty. You would either laugh in his face or recoil from him in disgust. Yet if a man guided his actions solely by his own advantage, you would have no objection at all to his conduct. Or suppose someone recommends a man to manage your affairs, saying you can trust him completely. To inspire your confidence, the person praises him as a prudent man who thoroughly understands his own interests. He is also tirelessly active and never misses a chance to advance those interests. Finally, the person praises his tasteful way of life, so you will not fear that he is crudely selfish. He does not seek pleasure in making money or in crude indulgence. Instead, he enjoys expanding his knowledge, having instructive conversations with a select circle, and even helping people in need. As for the means he uses, which of course get all their value from the end, he is not particular. He is ready to use other people's money for these purposes as if it were his own. He will do so, provided he knows he can use it safely and without being found out. You would either think the person recommending him was mocking you or had lost his senses. The boundaries between morality and self-love are so sharply and clearly marked that even the most ordinary eye can distinguish them. Such a person can tell whether something belongs to morality or self-love. The few remarks that follow may seem unnecessary when the truth is so plain. But at least they may help make the judgment of common sense a little clearer.

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 principle of happiness can provide maxims, but never maxims that could serve as laws of the will. This remains true even if universal happiness is made the goal. Our knowledge of happiness rests on purely empirical data. Each person's judgment about happiness depends greatly on their particular point of view, which is itself very changeable. The principle can therefore provide only general rules, not universal ones. In other words, it can provide rules that will fit most often on average. It cannot provide rules that must always and necessarily hold. So no practical laws can be based on it. In this case, an object of choice is the basis of the rule and must therefore come before it. For this very reason, the rule can concern only what is [felt]. It therefore concerns experience and is based on it, so the variety of judgments must be endless. The principle of happiness therefore does not prescribe the same practical rules to all rational beings. Yet the rules all fall under a common heading, namely, happiness. The moral law, however, is understood as objectively necessary only because it holds for everyone who 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 principle of self-love (prudence) only advises us. The moral law commands us. There is a great difference between what we are advised to do and what we are required to do.

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 hard 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.

Even a person of the most ordinary intelligence can easily and confidently see what to do under the principle of autonomy of the will. But under the principle of heteronomy of the will, it is difficult to see what to do. It takes knowledge of the world. In other words, duty is clear to everyone. But what will bring true, lasting advantage throughout a person's life is always hidden in impenetrable obscurity. And much prudence is needed to adapt a practical rule based on such advantage, with suitable exceptions, to the goals of life even reasonably well. But the moral law demands the most exact obedience from everyone. So it must not be so difficult to judge what the moral law requires that a person of the most ordinary, unpracticed understanding could not apply it correctly, even without worldly prudence.

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 he can do.

Everyone always has the power to obey morality’s categorical command. By contrast, it is rarely possible to follow the rule of happiness, which depends on experience. Not everyone can follow it, even for a single goal. The reason is that morality concerns only the principle guiding one’s action, which must be genuine and pure. Happiness, however, also depends on one’s ability and physical power to achieve a desired goal. It would be foolish to command everyone to try to make themselves happy. No one needs to be commanded to do what they invariably want to do anyway. We need only prescribe the means, or rather provide them, since people cannot do everything they wish. But it is quite rational to command morality in the name of duty. First, not everyone is willing to obey its rules when those rules go against their desires. And no one needs to be taught the means of obeying the moral law. In this respect, whatever a person wishes to do, they 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."

Someone who loses at a game may be annoyed with himself for being foolish. But if he knows he cheated, he must despise himself when he measures his actions against the moral law, even if cheating brought him a win. The moral law must therefore be different from the principle of personal happiness. A person must use a different standard when he is forced to say to himself, "I am a worthless person, though I have filled my purse," than when he approves of himself and says, "I am a prudent person, for I have increased my wealth."

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 he 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.

Finally, our practical reason includes another idea that accompanies the violation of a moral law: the wrongdoer deserves punishment. Now, punishment as such cannot be combined with receiving happiness. The person who inflicts punishment may also have the benevolent aim of directing it toward that end. But the punishment must first be justified in itself as punishment, that is, as mere harm. Suppose the punishment went no further, and the person punished saw no kindness hidden behind its harshness. Even then, that person would have to admit that justice had been done and that the penalty perfectly suited the conduct. In every punishment as such, justice must come first. Justice is essential to the idea of punishment. Benevolence may indeed be combined with punishment, but someone who deserves punishment has no reason at all to count on it. Punishment, then, is a physical harm. It may not be a natural consequence of moral wrongdoing, but moral law requires that it follow such wrongdoing. Now, every crime is punishable in itself, even apart from its physical consequences for the person who commits it. That is, every crime forfeits happiness, at least in part. So it is obviously absurd to say that the crime consists simply in bringing punishment upon oneself and thereby damaging one's own happiness. Yet this must be the proper idea of every crime under the principle of self-love. According to this view, punishment would be the reason for calling anything a crime. Justice, on the other hand, would consist in leaving every crime unpunished and even preventing any harm that naturally follows. For if all harm were prevented, there would no longer be any evil in the action. The harm that would otherwise have followed would have been prevented, and that harm was the only reason for calling the action evil. But to regard all rewards and punishments merely as tools in the hands of a higher power is to reduce the will to a mechanism that destroys freedom. On this view, rewards and punishments serve only to make rational creatures strive for their final end, happiness. The destruction of freedom is so evident that we need not dwell on it.

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.

More refined, but equally false, is the theory that a special moral sense, rather than reason, determines the moral law. According to this theory, awareness of virtue is directly connected with contentment and pleasure. Awareness of vice is connected with mental dissatisfaction and pain. This reduces everything to the desire for personal happiness. Without repeating what I have said above, I will simply point out the error in this theory. Its supporters imagine a wicked man tormented by mental dissatisfaction because he is aware of his wrongdoing. But to imagine this, they must first assume that his character is morally good, at least to some degree. Similarly, someone who is pleased by the awareness of acting rightly must already be virtuous. The idea of morality and duty must therefore come before any concern for this satisfaction. It cannot be derived from the satisfaction. A person must first appreciate the importance of what we call duty and the authority of the moral law. The person must also appreciate the immediate dignity that obeying the law gives someone in their own eyes. Only then can someone feel satisfaction in knowing they have obeyed it, and bitter remorse in knowing they have broken it. It is therefore impossible to feel this satisfaction or dissatisfaction before knowing what one is obliged to do. Nor can these feelings be the basis of that knowledge. A person must be at least half honest even to be able to conceive of these feelings. I do not deny that the human will, because it is free, can be directly determined by the moral law. Nor do I deny that frequently acting on this principle can at least produce a personal feeling of satisfaction. On the contrary, cultivating and developing this feeling is a duty. It alone deserves to be properly called moral feeling. But the idea of duty cannot be derived from it. Otherwise, we would have to assume a feeling for the law itself. We would thus make an object of sensation out of something that can only be thought by reason. And this, if it is not an outright contradiction, would destroy the whole idea of duty. In its place, it would put a mere mechanical interplay of refined inclinations, sometimes struggling against coarser ones.

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.

If we compare our supreme formal principle of pure practical reason, the autonomy of the will, with all earlier material principles of morality, we can display them all in a table. The table covers every possible case except the one formal principle. In this way, we can show clearly that it is pointless to look for any principle other than the one now proposed. For all possible principles that determine the will are either merely subjective, and therefore empirical, or also objective and rational. Both kinds of principle are either external or internal.

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 of 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.

The principles in the upper table are all empirical and clearly cannot provide the universal principle of morality. But those in the lower table are based on reason. Perfection as a quality of things can be thought of only through rational concepts. The same is true of the highest perfection conceived as a substance, that is, God. The first notion, perfection, may be understood in a theoretical sense. In that sense, it means only the completeness of each thing in its own kind (transcendental). Or it means the completeness of a thing merely as a thing (metaphysical). We are not concerned with either sense here. In a practical sense, perfection means a thing’s fitness or sufficiency for all kinds of purposes. As a quality of a human being, and therefore as something internal, perfection is nothing but talent. It also includes skill, which strengthens or completes talent. Supreme perfection conceived as a substance, that is, God, is external when considered practically. It is the sufficiency of this being for all ends. Ends must therefore be given first. Only in relation to those ends can perfection determine the will. This applies whether perfection is internal, in ourselves, or external, in God. But an end is an object that must come before the will is determined by a practical rule. It must also contain the ground that makes this determination possible. So it contains the matter of the will, taken as the principle that determines it. Such an end is always empirical. It may therefore serve the Epicurean principle of the happiness theory, but not the pure rational principle of morality and duty. Talents and their improvement can be motives only because we expect happiness from them. This is because they contribute to the advantages of life. The same holds for God’s will, if agreement with it is taken as the object of the will without any prior, independent practical principle. It follows, first, that all the principles stated here are material. Second, they include all possible material principles. Finally, material principles cannot provide the supreme moral law, as has been shown. So only the formal practical principle of pure reason can adequately provide categorical imperatives, that is, practical laws that make actions a duty. According to this principle, the mere form of universal legislation must be the supreme and immediate principle determining the will. It is also the only possible principle of morality, both for judging conduct and for application to the human will to determine it.

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.

This Analytic shows that pure reason can be practical. In other words, reason alone can determine the will, independently of anything empirical. The Analytic proves this through a fact in which pure reason shows itself to be practical in us. This fact is the autonomy shown in the fundamental principle of morality, through which reason determines the will to act.

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.

It also shows that this fact is inseparably connected with consciousness of the will’s freedom. Indeed, the two are identical. Through this consciousness, a rational being recognizes that its will belongs to the world of sense. As such, the will is necessarily subject to the laws of causality, like other causes that produce effects. Yet, as a being in itself, the rational being is also conscious of existing in an intelligible order of things. It is conscious, too, of being determined by that order. This consciousness does not come from any special intuition of itself. Instead, it comes from certain dynamic laws that determine how its will acts as a cause in the sensible world. For it has been proved elsewhere that if freedom is attributed to us, it places us in 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.

Now, if we compare this with the analytical part of the critique of pure speculative reason, we see a remarkable contrast. There, the starting point for a priori knowledge was not fundamental principles, but pure sensible intuition (space and time). Even so, this intuition made a priori knowledge possible only for objects of the senses. Synthetic principles could not be derived from concepts alone, without intuition. On the contrary, they could exist only in relation to this intuition and therefore to objects of possible experience. This is because only the concepts of the understanding, combined with this intuition, make possible the knowledge we call experience. Speculative reason rightly denied that it could have any positive knowledge beyond objects of experience, including things as noumena. Still, speculative reason established with certainty the concept of noumena. It established that we can, indeed must, think of them. For example, it showed against all objections that the assumption of freedom, considered negatively, was fully consistent with the principles and limits of pure theoretical reason. But speculative reason could not give us any definite increase in knowledge of such objects. On the contrary, it blocked any 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.

On the other hand, although the moral law gives us no direct view, it gives us a fact. This fact cannot be explained at all by anything in the sensible world or by our entire theoretical use of reason. It points to a pure world of understanding. Indeed, it defines that world positively and lets us know something about it: 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.

For rational beings, this law gives the sensible world, a system of nature perceived through the senses, the form of a world of understanding. That is, it gives the sensible world the form of a supersensible system of nature, without interfering with its mechanism. In the broadest sense, a system of nature is the existence of things under laws. The sensible nature of rational beings in general is their existence under laws conditioned by experience. From the standpoint of reason, this is heteronomy. The supersensible nature of these same beings, by contrast, is their existence according to laws independent of every condition of experience. These laws therefore belong to the autonomy of pure reason. The laws by which the existence of things depends on cognition are practical. So, as far as we can conceive of it, supersensible nature is simply a system of nature governed by the autonomy of pure practical reason. The law of this autonomy is the moral law. The moral law is therefore the fundamental law of a supersensible nature and a pure world of understanding. A counterpart of this world of understanding must exist in the sensible world, but without interfering with its laws. We might call the world of understanding the archetypal world (natura archetypa), which we know only through reason. We might call its counterpart the ectypal world (natura ectypa). For it contains the possible effect of the idea of the archetypal world, which determines the will. The moral law, in fact, places us in the idea of a system in which pure reason would produce the summum bonum, or highest good, if it had adequate physical power. The moral law also 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.

Even a little attention to ourselves proves that this idea really serves as the model for our decisions.

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.

When practical reason tests the maxim I am inclined to follow when giving testimony, I always consider it as a universal law of nature. Clearly, as such a law, it would require everyone to tell the truth. Statements cannot have the force of proof and still be deliberately false under a universal law of nature. Likewise, the maxim I adopt about my freedom to dispose of my own life is immediately determined when I ask a question. What must that maxim be so that a system governed by it can sustain itself? Clearly, in such a system, no one could arbitrarily end their own life. Such an arrangement would not be a lasting order of things. The same applies in all similar cases. Now, in nature as we actually experience it, free will does not by itself determine us to follow maxims that could form the basis of a natural system of universal laws. Nor does it by itself determine us to follow maxims that could even fit into such a system. Instead, its maxims are private inclinations. These do form a natural whole governed by pathological (physical) laws. But they could not form part of a system of nature that could exist only through our will acting according to pure practical laws. Yet reason makes us aware of a law to which all our maxims are subject. It is as though our will must bring a natural order into being. This law must therefore be the idea of a natural system that is not given in experience, yet is possible through freedom. The system is therefore supersensible. We give it objective reality, at least from a practical point of view, because we regard 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.

A natural system can subject the will to its laws, or it can be subject to a will. In the latter case, the system is subject to the will only in relation to the will’s free actions. The difference between their laws is this: in the first system, objects must cause the ideas that determine the will. In the second system, the will causes the objects. The principle that determines how the will causes objects lies solely in the pure faculty of reason. This faculty may therefore be called 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).

There are therefore two very different problems. The first is how pure reason can know objects a priori, or independently of experience. The second is how pure reason can directly determine the will. In other words, how can pure reason determine a rational being’s power to bring objects into existence? It would do so through the mere thought that its own maxims are universally valid 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 former, which belongs to the critique of pure speculative reason, first requires an explanation of how intuitions are possible a priori. Without intuitions, no object can be given, and therefore none can be known synthetically. The answer is that all these intuitions are merely sensible. They therefore make no speculative knowledge possible beyond the reach of possible experience. All the principles of pure speculative reason can therefore serve only to make experience possible. This is either experience of given objects or of objects that may be given ad infinitum, but are never 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.

The latter belongs to the critique of practical reason. It does not need to explain how the objects of desire are possible. That is a question about theoretical knowledge of nature, and it is left to the critique of speculative reason. The critique of practical reason only needs to explain how reason can determine the maxims of the will. It asks whether reason does this only through empirical ideas as determining principles. Or can pure reason be practical and serve as the law of a possible order of nature that cannot be known empirically? Such a supersensible order of nature is possible. Our conception of it can also be the basis of its reality through our own free will. Its possibility requires no a priori intuition of an intelligible world. Such an intuition would be impossible for us because it would be supersensible. The question concerns only the principle that determines acts of will in their maxims. Is this principle empirical, or is it a concept of pure reason, with the lawlike character that belongs to pure reason generally? And how can it be such a concept? It is for the theoretical principles of reason to decide whether the will can cause its objects to become real. That is a question about the possibility of the objects we will. Intuition of these objects is therefore unimportant to the practical problem. Here we are concerned only with how the will is determined and with the principles that determine its maxims as a free will. We are not concerned with the result at all. As long as the will conforms to the law of pure reason, its power to carry out its aims does not matter here. The critique is not concerned with whether these lawgiving maxims actually produce a possible order of nature. It asks only whether pure reason can be practical, and how it can be practical. In other words, it asks whether and how pure reason can 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.

In this inquiry, the critique may and must begin with pure practical laws and their reality. But instead of intuition, it bases these laws on the concept of their existence in the intelligible world. That is the concept of freedom. This concept has no other meaning, and these laws are possible only in relation to freedom of the will. But if freedom is assumed, the laws are necessary. Conversely, freedom is necessary because these laws are necessary as practical postulates. We cannot explain further how this consciousness of the moral law, or, what amounts to the same thing, consciousness of freedom, is possible. But the theoretical critique has firmly established that such consciousness is admissible.

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.

The explanation of the supreme principle of practical reason is now complete. First, I have shown what the principle contains, and that it stands on its own, entirely a priori and independent of empirical principles. I have also shown how it differs from all other practical principles. Its deduction, however, is another matter. By deduction, I mean justifying the principle’s objective and universal validity and understanding how such a synthetic a priori proposition is possible. We cannot expect to succeed as well here as we did with the principles of pure theoretical reason. Those principles concerned objects of possible experience, namely phenomena. We could prove that phenomena could be known as objects of experience only if they were brought under the categories according to these laws. Consequently, all possible experience had to conform to these laws. But I could not use this method to deduce the moral law. The moral law does not concern knowledge of the properties of objects that may be given to reason from another source. Instead, it concerns knowledge that can itself be the basis for the existence of objects. Through this knowledge, reason in a rational being has causality. This is pure reason, which can be regarded as a faculty that directly determines 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.

All human understanding comes to an end when we reach fundamental powers or faculties. We have no way to understand how these are possible. Nor should we invent them arbitrarily and assume they exist. Therefore, when reason is used theoretically, experience alone can justify assuming that such faculties exist. But we cannot use empirical evidence instead of a deduction from a priori sources of knowledge in this case. The case concerns reason's pure practical faculty. For anything whose reality must be proved through experience must also depend on principles of experience for its possibility. Yet pure practical reason, by its very definition, cannot be regarded as depending on such principles. Furthermore, the moral law is given as a fact of pure reason. We are conscious of the moral law a priori, and it is apodeictically certain. This is so even if we grant that experience offers no example of the law being fulfilled exactly. Hence, theoretical reason cannot prove the objective reality of the moral law through any deduction, whether speculative or supported by experience. Even if we gave up its apodeictic certainty, the moral law could not be proved a posteriori through experience. Yet the moral law is firmly established in 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.

But the search for a deduction of the moral principle leads nowhere. Instead, we find something quite unexpected. The moral principle serves, conversely, as the basis for deducing an inscrutable faculty. No experience could prove that this faculty exists, but speculative reason had to assume at least that it was possible. Otherwise, speculative reason would have contradicted itself by failing to find the unconditioned in the chain of causality among its cosmological ideas. I mean the faculty of freedom. The moral law itself requires no justification. It proves not only that freedom is possible, but also that freedom actually belongs to beings who recognize the moral law as binding on them. The moral law is a law of causality for free agents and, therefore, for the possibility of a supersensible system of nature. In the same way, the metaphysical law of events in the world of sense was a law of causality for the sensible system of nature. The moral law therefore determines what speculative philosophy had to leave undetermined: the law for a kind of causality whose concept in speculative philosophy was only negative. In this way, the moral law gives this concept objective reality for the first time.

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 moral law has this credential: it serves as a principle for establishing freedom, a causality of pure reason. This is a sufficient substitute for any a priori justification. Theoretical reason was compelled to assume at least the possibility of freedom to satisfy a need of its own. The moral law establishes the reality of freedom in a way that even satisfies the critique of speculative reason. It does so by giving a positive definition to a causality previously understood only in negative terms. Speculative reason could not understand how this causality was possible, yet it was compelled to assume it. The moral law adds the idea of a reason that directly determines the will. Reason does this by requiring the will’s maxims to have a universal legislative form. In this way, the moral law can for the first time give reason objective, though only practical, reality. Reason always went beyond the bounds of experience when it tried to use its ideas speculatively. The moral law thus changes this transcendent use of reason into an immanent one. Through ideas, reason itself becomes 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 law of causality (of the will) has self causality, or is its determining principle.

The causality of beings in the world of sense, considered as such, can never be determined without conditions. Yet every series of conditions must have something unconditioned. So there must be a causality determined entirely by itself. The idea of freedom as a capacity for absolute spontaneity was therefore not found lacking. As far as its possibility was concerned, it was an analytic principle of pure speculative reason. But we cannot possibly find an example in experience that corresponds to this idea. Among the causes of things as phenomena, we could never find an absolutely unconditioned determination of causality. We could therefore only defend the supposition that a freely acting cause might be a being in the world of sense. We could do so insofar as that being is also considered from another point of view, as a noumenon. We showed that there is no contradiction in regarding all its actions as subject to physical conditions insofar as they are phenomena. At the same time, we could regard its causality as physically unconditioned insofar as the acting being belongs to the world of understanding. In this way, we made the concept of freedom a regulative principle of reason. This principle does not tell me what the object is to which that kind of causality is attributed. But it removes the difficulty. On one side, I allow the mechanism of physical necessity to trace every condition back to another condition without end. It can do so in explaining events in the world, including the actions of rational beings. On the other side, I leave open a place that is vacant for speculative reason, namely, the intelligible realm. I do so in order to assign the unconditioned to that realm. But I could not verify this supposition. That is, I could not turn it into knowledge of a being that acts freely, or even into knowledge of such a being's possibility. Pure practical reason now fills this vacant place with a definite law of causality in an intelligible world. This is the moral law, a law of causality through freedom. Speculative reason gains no insight from this. It gains only certainty about its problematic notion of freedom. That notion now gains objective reality. Although this reality is only practical, it is nevertheless beyond doubt. Even the notion of causality is not enlarged so that its use extends beyond its proper limits. Its application, and therefore its meaning, properly holds only in relation to phenomena, connecting them into experiences. The Critique of Pure Reason shows this. If reason sought to go beyond these limits, it would have to show something more. It would have to show how the logical relation of principle and consequence can be used synthetically in a kind of intuition other than sensible intuition. In other words, it would have to show how a causa noumenon is possible. Reason can never do this. As practical reason, it does not even concern itself with this question. It only places the determining principle of human causality in pure reason, which is therefore called practical. Human causality, as the causality of a sensible creature, is given. Practical reason therefore uses the notion of cause not to know objects, but to determine causality in relation to objects in general. Practical reason can set aside entirely the application of this notion to objects for the sake of theoretical knowledge. For this concept is always found a priori in the understanding, even independently of any intuition. Reason uses the concept only for a practical purpose. We can therefore place the determining principle of the will in the intelligible order of things. At the same time, we admit that we cannot understand how the notion of cause can determine our knowledge of those things. But reason must know causality in a definite way with respect to the will's actions in the sensible world. Otherwise, practical reason could not actually produce any action. Reason forms a notion of its own causality as noumenon. But it need not determine that notion theoretically, for the sake of knowing its supersensible existence, in order to give the notion meaning. For the notion gains meaning apart from such knowledge, though only for practical use, through the moral law. Theoretically considered, the notion of causality remains a pure a priori concept of the understanding. It can be applied to objects whether or not they have been given through the senses. But when they have not been so given, it has no definite theoretical meaning or application. It is then only a formal, though essential, concept of the understanding relating to an object in general. The meaning reason gives it through the moral law is merely practical. For the idea of the law of causality of the will itself has causality, or is the will's determining principle.

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 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?

The moral principle we have presented gives us a law of causality. Its determining principle lies beyond all the conditions of the sensible world. Through this law, we can understand how the will, as part of the intelligible world, can be determined. The critique of speculative reason allowed us to conceive of man, the subject of the will, as belonging to a world of pure understanding. It also showed that man is unknown to us in this respect. But now we can also define man's causality through a law that cannot be reduced to any physical law of the sensible world. Our knowledge therefore extends beyond the limits of the sensible world. The Critique of Pure Reason declared that any such claim would be futile in all speculation. How, then, can the practical use of pure reason be reconciled with its theoretical use when defining the limits of its power?

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 often 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.

David Hume, we may say, began the attack on the claims of pure reason that made a thorough investigation necessary. He argued as follows: The concept of cause involves a necessary connection between the existence of different things, precisely as different things. Given A, I know that something quite distinct from it, namely B, must also exist. But a connection can be called necessary only if it is known a priori. Experience can tell us only that a connection exists, not that it necessarily exists. Hume says that we cannot know a priori that a connection between one thing and another is necessary when they have not been given in experience. The same applies to a connection between one attribute and another quite distinct attribute. Therefore, the concept of cause is invented and misleading. To put it mildly, it is an illusion. The illusion is excusable only because we grow accustomed to perceiving certain things or their attributes together or in succession. We then gradually mistake this habit, a subjective necessity, for an objective necessity to suppose such a connection in the objects themselves. Thus, the concept of cause has been acquired by stealth, not legitimately. Indeed, it can never be acquired legitimately or validated. It demands a connection that is itself empty, fanciful, and indefensible before reason, and to which no object can ever correspond. In this way, empiricism was first introduced as the sole source of principles for all knowledge of the existence of things. Mathematics was therefore excluded. With empiricism came the most thorough skepticism, even about the whole science of nature (as philosophy). For on these principles, we can never infer a consequence from given attributes of existing things. Such an inference would require the concept of cause, which involves the necessity of the connection. Guided by imagination, we can only expect similar cases. This expectation is never certain, however often it has been fulfilled. We could not say of any event that a certain thing must have preceded it and that the event necessarily followed from it. In other words, we could not say that the event must have a cause. We might know of many cases with such a preceding event, enough to derive a rule from them. Even so, we could never suppose that events always and necessarily happen according to that rule. We would therefore have to leave room for blind chance, which brings all use of reason to an end. This firmly establishes skepticism about arguments that reason from effects back to causes and makes that skepticism 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.

Mathematics has escaped harm so far because Hume thought its propositions were analytic. He thought they moved from one property to another by identity, and therefore by the principle of contradiction. But this is not the case. Mathematical propositions are synthetic. Geometry, for example, does not deal with whether things exist, but only with their a priori properties in a possible intuition. Even so, geometry proceeds just as reasoning about causation does. It moves from one property (A) to a wholly distinct property (B), as necessarily connected with the first. Nevertheless, mathematical science must finally fall under this empiricism, despite its much-praised apodeictic certainty. It must fall for the same reason that led Hume to put custom in place of objective necessity in causation. Despite all its pride, mathematics must agree to lower its bold claim to acceptance a priori. It must depend instead on the kindness of observers to secure acceptance of its propositions as universally true. When called as witnesses, the observers would surely readily admit that they have always found the geometer's theorems to be true. And so, although the theorems are not necessarily true, the observers would allow us to expect them to remain true. In this way, Hume's empiricism inevitably leads to skepticism, even about mathematics. It therefore leads to skepticism about every scientific theoretical use of reason. For every such use belongs either to philosophy or to mathematics. With the chief branches of knowledge so terribly overthrown, will common reason fare any better? Or will common reason instead become hopelessly entangled in this destruction of all knowledge? If so, the same principles would lead to universal skepticism, though it would affect only the learned. I 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.

My own critical examination of pure reason was prompted by Hume's skeptical teaching. But it went much further, covering the whole field of pure theoretical reason in its synthetic use. It therefore covered the whole field of what is generally called metaphysics. I approached the Scottish philosopher's doubts about causality in the following way. If Hume took the objects of experience to be things in themselves (as is almost always done), he was quite right to call the concept of cause a deception and an illusion. For when it comes to things in themselves and their attributes as such, we cannot see why B, which differs from A, must necessarily be given whenever A is given. Hume could therefore not accept such a priori knowledge of things in themselves. Still less could this acute writer accept that the concept of causality came from experience. That would directly contradict the necessary connection that is essential to the concept. The concept was therefore rejected, and custom took its place 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.

My inquiries showed, however, that the objects we deal with in experience are not things in themselves, but only phenomena. With things in themselves, we cannot see why supposing A would require us also to suppose B, which is quite different from A. In other words, we cannot see why A as cause must necessarily be connected to B as effect. Yet we can conceive that A and B, as phenomena, may be necessarily connected in a certain way within one experience. They might, for example, be connected by their relations in time. They could then not be separated without contradicting the connection that makes this experience possible. In this experience they are objects, and only in this experience can we know them. I found that this was indeed the case. I was therefore able to prove that the concept of cause has objective reality in relation to objects of experience. I was also able to deduce it as an a priori concept, because of the necessary connection it implies. In other words, I could show how the concept could originate in pure understanding, without any source in experience. Having removed the source of empiricism, I could also overthrow its inevitable consequence, scepticism. I did so first with regard to physical science and then with regard to mathematics, where empiricism has just the same grounds. Both sciences concern objects of possible experience. In this way, I also overthrew the thorough doubt of whatever theoretical reason claims 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.

But how can the category of causality apply to things beyond the bounds of possible experience? The same question applies to all the other categories, since without them we can know nothing that exists. I was able to establish the objective reality of these concepts only for objects of possible experience. But I have preserved these concepts by proving that they can be used to think about objects, though not to determine them a priori. This gives them a place in the pure understanding, through which they refer to objects in general, whether sensible or not. What is still missing is intuition. Intuition is the condition for applying these categories, especially causality, to objects. Where intuition is not given, we cannot apply the categories to gain theoretical knowledge of an object as a noumenon. Anyone who attempts to do so is therefore absolutely forbidden, as in the Critique of Pure Reason. Still, the concept of causality retains its objective reality and can be used even for noumena. But we cannot define the concept theoretically in any way that produces knowledge. The concept contains nothing impossible, even when it refers to an object. This was shown by the fact that its place was firmly established in the pure understanding, even when applied to objects of sense. Things in themselves cannot be objects of experience. When the concept of causality refers to them, it cannot be determined so as to represent a definite object for theoretical knowledge. Yet for another purpose, such as a practical one, it might be capable of being determined so that it can be applied to them. This would not be possible if, as Hume maintained, the concept of causality contained something absolutely impossible to think.

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.

To discover the condition for applying this concept to noumena, we need only recall why we want to apply it to things in themselves, not just to objects of experience. We will see that a practical purpose, not a theoretical one, makes this necessary. Even if we succeeded in applying the concept through speculation, we would gain no real knowledge of nature or of objects given to us. Instead, we would take a great leap from what is conditioned by the senses to the supersensible. We would do this to complete our knowledge of principles and establish its limits. Yet within the realm of the senses, we already have enough to do to hold our ground and carefully trace the chain of causes. And an infinite gap would remain between those limits and what we know. We would have followed idle curiosity rather than a genuine desire for 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.

Besides its relation to objects in theoretical knowledge, the understanding also relates to the faculty of desire. In this relation, the faculty of desire is called the will. It is called the pure will insofar as pure understanding is practical through the mere conception of a law. In this practical role, pure understanding is called reason. The moral law gives us the objective reality of a pure will, or, equivalently, of pure practical reason, a priori. It gives us this reality, as it were, by means of a fact. For we may call an inevitable determination of the will a fact, although it does not rest on empirical principles. Now, the concept of a will already contains the concept of causality. So the concept of a pure will contains the concept of causality accompanied by freedom. This causality cannot be determined by physical laws. Consequently, its reality cannot be proved by any empirical intuition. Nevertheless, the pure practical law fully establishes its objective reality a priori. Clearly, it establishes this reality for the practical use of reason, not for its theoretical use. Now, the concept of a being with a free will is the concept of a causa noumenon. We are already assured that this concept involves no contradiction. For the concept of cause arises entirely from pure understanding. Its objective reality is established by the deduction, and its origin is independent of all sensible conditions. Therefore, the concept of cause is not restricted to phenomena, unless we want to make a definite theoretical use of it. It can equally be applied to things that are objects of pure understanding. But this application cannot rest on any intuition, since intuition can only be sensible. So, for the theoretical use of reason, causa noumenon is an empty concept, although it is possible and thinkable. Now, I do not use this concept to understand theoretically the nature of a being insofar as it has a pure will. It is enough for me to designate such a being and thereby combine the concept of causality with that of freedom. I also combine causality with what is inseparable from freedom, the moral law, as its determining principle. I certainly have the right to do this because the concept of cause has a pure, non-empirical origin. For I do not consider myself entitled to use it except in relation to the moral law, which determines its reality. In other words, I consider myself entitled to use it only practically.

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.

If, like Hume, I had denied the concept of causality all objective reality in its theoretical use, it would have lost all meaning. This would be so if I had denied it objective reality not only for things in themselves (the supersensible), but also for objects of the senses. The concept would then have been theoretically impossible and declared entirely useless. Since nothing cannot be used, it would have been absurd to put a theoretically meaningless concept to practical use. But the concept of causality free from empirical conditions is theoretically possible, although it is empty. By empty, I mean that it has no corresponding intuition. The concept also refers to an indeterminate object. On the other hand, the moral law gives the concept meaning, and therefore gives it practical meaning. I have no intuition that could establish the concept’s objective theoretical reality. Nevertheless, the concept has a real application, shown concretely in intentions or maxims. In other words, it has a practical reality that can be specified. This is enough to justify the concept even with respect 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.

Once we establish the objective reality of a pure concept of the understanding in the supersensible realm, it also gives objective reality to all the other categories. But it does so only insofar as they are necessarily connected with the determining principle of the will, the moral law. Their reality permits only practical application. It does not enlarge our theoretical knowledge of these objects or our understanding of their nature through pure reason in the least. As we shall see later, these categories refer only to beings as intelligences, and only to the relation of reason to the will in those beings. They therefore refer only to what is practical and cannot claim to give us any further knowledge of these beings. Other properties belonging to the theoretical representation of supersensible things may be connected with these categories. But this connection does not count as knowledge. It gives us only a right to admit and assume that such beings exist. From a practical point of view, however, we must do so. This holds even when we conceive of supersensible beings, such as God, by analogy. Such an analogy is a purely rational relation that we use practically in relation to what is sensible. Applying these categories to the supersensible solely from a practical point of view therefore gives pure theoretical reason no encouragement at all to run wild into the transcendent.