Critique of Practical Reason

Critique of Practical Reason

by Immanuel Kant

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The late Dr. Heinrich (Heinz) W. Cassirer was the elder son of the famous German philosopher and polymath, Ernst Cassirer. The family took refuge in Britain following the Nazi accession to power in 1933, being Jewish and therefore in obvious, ultimate danger. Professor Cassirer came to Oxford, but not long afterwards he moved to Sweden and then to the U.S.A. His son,…  See more details below


The late Dr. Heinrich (Heinz) W. Cassirer was the elder son of the famous German philosopher and polymath, Ernst Cassirer. The family took refuge in Britain following the Nazi accession to power in 1933, being Jewish and therefore in obvious, ultimate danger. Professor Cassirer came to Oxford, but not long afterwards he moved to Sweden and then to the U.S.A. His son, Heinz, remained in Britain, becoming a protege of the distinguished British Kantian scholar, Professor H. J. Paton, then professor of logic and metaphysics in the University of Glasgow. At Paton's suggestion, Heinz Cassirer wrote a commentary on Kant's third Critique, the Critique of Judgment, which Methuen published in the late thirties; he also assisted Professor Paton with the last stages of the preparation of the latter's commentary on the first half of Kant's Critique of Pure Reason, which he brought out in the autumn of 1936 under the title of Kant's Metaphysic of Experience. In 1937 Paton moved to Oxford as White's Professor of Moral Philosophy, and Cassirer followed him there to teach as a refugee scholar, concentrating on Kant's philosophy. In 1946 he secured a permanent appointment in the Department of Moral Philosophy at Glasgow under the late Professor W. G. Maclagan, remaining there until his retirement. In 1954 he published, in the Muirhead Library of Philosophy series, a study on Kant's Critique of Pure Reason under the title: Kant's First Critique. But he was already working on the relation of Kant's theory of knowledge to his ethics, and the first draft of the translation of the Critique of Practical Reason, which now appears posthumously, was completed in 1945.

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A translation of Kant's Kritik der praktischen Vernunft, completed by H. W. Cassirer in 1976 (his first draft was written 30 years earlier), and lightly prepared for publication posthumously by editors G. Heath King and Ronald Weitzman. Cassirer aimed to provide a technically accurate rendering of Kant's text which is attentive to the spirit as well as the letter of Kant's original, while showing the movement of his thinking as it unfolds. Annotation c. by Book News, Inc., Portland, Or.

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By Immanuel Kant, Thomas Kingsmill Abott

Dover Publications, Inc.

Copyright © 2014 Dover Publications, Inc.
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ISBN: 978-0-486-11302-9




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


Supposing that pure reason contains in itself a practical motive (126), 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, (127). 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 on 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 (128); it is the volition only which is to be determined à priori by that rule. If now it is found that this rule is practically right, then it is a law, because it is a categorical imperative. Thus, practical laws refer to the will only, without considering what is attained by its causality, and we may disregard this latter (as belonging to the world of sense) in order to have them quite pure.


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

By the matter of the faculty of desire I mean an object the realization of which is desired. Now, if the desire for this object precedes the practical rule, and is the condition of our making it a principle, then I say (in the first place) this principle is in that case wholly empirical, for then what determines the choice is the idea of an object, and that relation of this idea to the subject by which its faculty of desire is determined to its realization. Such a relation to the subject is called the pleasure in the realization of an object. This, then, must be presupposed as a condition of the possibility of determination of the will. But it is impossible to know à 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.

(129) 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 à priori); it follows, therefore, that such a principle can never furnish a practical law.


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

Pleasure arising from the idea of the 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 (130), inasmuch as they all belong to the principle of self-love or private happiness.


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


It is surprising that men, otherwise acute, can think it possible to distinguish between higher and lower desires, according as the ideas which are connected with the feeling of pleasure have their origin in the senses or in the understanding; for when we inquire what are the determining grounds of desire, and place them in some expected pleasantness, it is of no consequence whence the idea of this pleasing object is derived, but only how much it pleases. Whether an idea has its seat and source in the understanding or not, if it can only determine the choice by presupposing a feeling of pleasure in the subject, it follows that its capability of determining the choice depends altogether on the nature of the inner sense, namely, that this can be agreeably affected by it. However dissimilar ideas of objects may be, though they be ideas of the understanding, or even of the reason in contrast to ideas of sense, yet the feeling of pleasure, by means of which they constitute the determining principle of the will (the expected satisfaction which impels the activity to the production of the object) (131), 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 (132). 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 super-subtle 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 (133) which is content to know something of everything and nothing thoroughly, so as to please every party.

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


To be happy is necessarily the wish of every finite rational being, and this, therefore, is inevitably a determining principle of its faculty of desire. For we are not in possession originally of satisfaction with our whole existence—a bliss which would imply a consciousness of our own independent self-sufficiency—this is a problem imposed upon us by our own finite nature, because we have wants, and these wants regard (134) 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 the 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 purposes), but in that case they are merely theoretical principles; as, for example, how he who would like to eat bread (135) 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 of pleasure and pain, which can never be supposed to be universally directed to the same objects.


Excerpted from CRITIQUE OF PRACTICAL REASON by Immanuel Kant, Thomas Kingsmill Abott. Copyright © 2014 Dover Publications, Inc.. Excerpted by permission of Dover Publications, Inc..
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