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On the so-called “discrepancies” between Utilitarian
and Kantian Ethics



Utilitarian and Kantian ethics are two of the most influential classical ethical theories. When moral philosophers talk about what is the right thing to do or what is the meaning of right, duty, freedom and responsibility, they never fail to refer to either or both of these theories. And even today, when we debate over practical issues in bioethics such as euthanasia, abortion, and research using human embryos, or other issues such as freedom of expression or justification of war, one or the other of these theories is frequently cited as the foundation of rational moral reasoning1.

Despite all this, these two ethical theories, Utilitarianism and Kantianism, are usually depicted as acutely opposed to and severely incompatible with each other. This discrepancy is taken for granted and hardly questioned. But if Utilitarian and Kantian ethics disagree, on what points and to what extent exactly do they conflict?

In this paper, I will provide a clear picture of the precise relation between these two ethical theories. Although it is commonly believed that Utilitarian and Kantian ethics occupy opposite poles of moral philosophy, I will argue that they are much more similar than previously assumed. The two theories share not one but several important ideas, all of which are essential elements for both.

To accomplish this task, I will discuss Henry Sidgwick’s Methods of Ethics, and Immanuel Kant’s three ethical writings, Grundlegung zur Metaphysik der Sitten, Kritik der praktischen Vernunft, and Metaphysik der Sitten, as major texts for Utilitarian and Kantian ethics, respectively2. Although Jeremy Bentham and John Stuart Mill are more widely known classical Utilitarians, I chose Sidgwick mainly because his analyses of the philosophical basis of Utilitarianism seem to be the most elaborate and most sophisticated, as John Rawls acknowledged in his Theory of Justice3. Among 20th-century utilitarians, the late professor R.M. Hare is the well-known moral philosopher who has advocated the affinity between his Utilitarian theory and Kant’s ethics. I have to admit that I have been strongly influenced by professor Hare, though I hope I clarified more in detail the relationship between Utilitarian and Kantian ethics by examining Henry Sidgwick’s argument, which I think is even more accurate than Hare’s as to the theoretical structure of Utilitarianism, and comparing it with Kant’s original writings4. Once we carefully compare their original texts, we will find that the differences between Utilitarian theory and Kant’s ethics are overstated. Notice I do not deny that there are some differences between the two. A few differences in their theoretical structure will certainly remain; one is their treatment of the notion of freedom, and another relates to their methods of theory construction using very similar points, which led to quite different practical claims. The question of freedom is too complex to discuss in this paper, but I will closely examine the theoretical constructions of both philosophies. Even this limited investigation will show how most of the clichéd discrepancies disappear. The possibility of reconciling Utilitarians and Kantians will depend on whether we see such few differences as crucial or not.

1. A common picture of the divergence

Utilitarianism is the view that a morally right act, or an act that ought to be done, is the one that will bring about more overall happiness or satisfaction for all the people affected by the action than any viable alternatives. “Happiness” in this context refers to any kind of agreeable feelings in a broad sense, a state of mind that a person thinks desirable and in which a person feels satisfied, including not only sensual pleasure but also all kinds of enjoyment, amusement, gratification and satisfaction. This view is a version of Consequentialism, for it thinks that the morally right act is the one which tries to bring about the best possible consequence, that is, as much happiness or preference satisfaction as possible for the people concerned. And its claim about ultimate good, that happiness is the ultimate end of moral action, is called ethical Hedonism. Some contemporary Utilitarians use the term “preference satisfaction”, but Sidgwick and classical Utilitarians use the term happiness and are therefore called hedonistic Utilitarians.

Whether the hedonistic or preference version is considered, it is frequently said that Utilitarian ethics is obviously opposed to Kantian ethics. For example, Richard Norman writes that any marriage of Utilitarian and Kantian ethics is against the whole spirit of Kant’s ethics, which always puts emphasis on the irrelevance of consequences and happiness5. The Encyclopedia of Kant also explains Utilitarianism by saying that “Kant took a deontological position, and from that viewpoint criticized Utilitarianism which holds the consequentialist principle, as a version of heteronomous morality because it relies on a material moral principle”6. J. S. Mill interpreted Kant’s fundamental formula of the Categorical Imperative (explained later) as harmonizing with Utilitarianism by paraphrasing the formula as: “we ought to shape our conduct by a rule which all rational beings might adopt with benefit to their collective interest7. However, Mill’s interpretation is generally objected to in that “Kant’s fundamental principles will never allow Mill’s interpretation… That would deny Kant’s unique idea of Categorical Imperative and turn all norms into mere hypothetical Imperatives”8.

One salient feature of Kant’s ethics lies in his effort to find some supreme principle of morals, which should be found by eliminating all the empirical factors.

Kant clearly distinguishes moral duty from a person’s empirical desire. For him, moral duty is something in which one’s reason determines one’s will to act in a certain way regardless of one’s own personal desires. Will (Wille) and desire (Begierde) are similar in that both are related to choice, but unlike personal desires or inclinations (i.e., habitual desires), will is said to be “a capacity to determine itself to acting in conformity with the representation of certain laws9.

Thus, it is not a personal liking but Reason that determines will in conformity with laws. To determine a will or an act means determining what such a will or an act ought to be. Kant suggests in one place that the theoretical determination of an object is about what it is in itself and the practical determination of it is about “what the idea of it ought to be for us and for its purposive use”10. In another place he talks about “the determination of action that is necessary in accordance with the principle of a will which is good in some way”, adding that the imperative which formulates such a determination of will “says which action possible by me would be good”11. These phrases indicate that the word "determine" in practical context is related to choosing a good act, or act that ought to be done, among possible alternatives.

In accordance with the distinction between inclinations and rational will, Kant also distinguishes between a maxim and a law. Propositions that contain a general determination of will are called practical principles (Grundsatz), but when the subject regards the condition of the principle as holding only for his own will, they are called maxims (Maxim); however, when the condition is recognized as holding for the will of every rational being, practical principles are called practical laws (Gesetz)12. Maxims are the principles in accordance with which the subject acts, but practical laws are the principles in accordance with which the subject ought to act. Kant argues that God, for example, feels no imperatives because he has no opposing inclinations; however, for beings who have impulses or inclinations that might be against those laws, practical laws are represented as imperatives13.

Maxims are also principles, but those do not necessarily hold for every rational being. Only the categorical imperatives, which hold unconditionally regardless of any incidental and subjective conditions that distinguish each rational individual, are rightly called practical laws, which are supposed to hold objectively and universally14.

Taking such a standpoint, Kant assumes that the supreme principle (s) of morals, which he tries to seek, must not rely on the objects of personal desires, and must not depend on any empirical conditions. According to Kant, you cannot derive a law that holds for every rational being from any precept that is based on the principles of mere experience, or any precept that rests on empirical grounds, even if the precept is universal in a certain respect15. Again, practical principles that presuppose some object of choice (which is in Kant’s term matter, meaning the object of desire) as the grounds for the determination of will, are all empirical and cannot become practical laws16. If the determining grounds of will were some matter in Kant’s sense, the principle of the will must depend on empirical conditions such as whether the object will be realized or not, whether it will bring about pleasure or not, and so on, and it would not have held for every rational being without exception.

Thus, Kant excludes all kinds of empirical and material principles, and finally presents his Formulae of the Categorical Imperative as the supreme principles of morals, as follows:

The Fundamental Formula of Categorical Imperative, or the Formula of Universal

Law:Act only in accordance with that maxim through which you can at the same time will that it become a universal law17.

The Formula of an End in Itself: So act that you use humanity, whether in your own

person or in the person of any other, always at the same time as an end, never merely as a means18.

The Formula of Autonomy: “[Act in accordance with] the idea of the will of every

rational being as a will giving universal law19.

These three formulae are sufficiently well known as to forgo much detailed explanation20. These are a priori laws, which hold universality and absolute necessity that cannot derive from any experience21. Kant says that our maxims cannot be moral ones if they do not conform with these laws, and that we can tell what ought not to be done, what is allowed, and what are our duties, by testing our own maxims against these formulae. Kant insists that moral law must be the authority for determining our will, and also be the incentive of the same will22. A moral act should be done not out of selfish interest, but out of respect for the law, and we should act according to what we have determined to be universal moral law, even if doing so restricts or frustrates our own inclinations. To act morally is not to act in pursuit of happiness, but in order to deserve happiness23.

A further feature of Kant’s ethics is his insistence of a close relationship between morality and freedom, which leads to his emphasis on the practical significance of freedom. According to Kant, the notion of Freedom has two aspects; the negative concept of Freedom means the absence of the influence of sensible impulse in one's will, and a positive concept denotes “the will’s property of being a law to itself” and “pure Reason’s capacity to be practical by itself”24. The positive sense of Freedom, acting solely according to Reason, is what Kant would like to emphasize because it clarifies our excellent nature of autonomy, but this sense of Freedom is possible only if the negative sense, being free from desire or impulse, is first present. Kant suggests that our will must be free to present moral law without the influence of empirical conditions, in order for moral law to exist. He further believes that to find moral laws within ourselves enables us to realize that we are free to act based solely on Reason25. Kant also asserts that every rational being having a will must act under this idea of freedom26.

From the above explanation, Kant’s ethics may appear to be quite different from those of Utilitarianism. The alleged contrast between the two may be depicted as follows:

  1. Total difference in their fundamental moral principles. Utilitarians support the Utilitarian Principle, which tells us to maximize people's happiness, whereas Kant presents the Formulae of Categorical Imperatives as fundamental moral principle(s).

  1. The grounds for the determination of moral will. For Utilitarians, the determining basis of moral will is happiness, which is empirical and material. But Kant insists that such grounds must be nothing other than the moral law that is not borrowed from experience, so he would undoubtedly criticize the Utilitarian idea.

  1. Consequentialism vs. deontology, or the priority of the Good over the Right. Utilitarians judge the rightness or wrongness of an act by considering its expected effects. But for Kant, the moral value of an act stems not from its expected consequences, but from the representation of law itself27. To put it in another way, Utilitarianism first considers each individual's happiness as the end or the good that ought to be aimed for, and from that consideration derives the rightness of the act, whereas in Kant's ethics the notion of good (or bad) is subordinate to and regulated by moral laws28.

  1. Attitudes towards Hedonism. Hedonism is a central claim of classical Utilitarianism. But Kant insists that moral will must not be determined by happiness. According to Kant, the cognition of happiness relies on empirical facts; therefore, the principle of happiness is far from being qualified as a universal law of will. It is conceivable that the desire for happiness is universal, but the objects desired are quite different among individuals. Individuals’ desires may sometimes coincide, but that is simply an incidental phenomenon and is not always true. And it is impossible to find a universal law that governs those diverse inclinations29. One might object that Utilitarianism’s central goal is to bring about people’s collective happiness, and not self-centered individual happiness, of which the latter notion Kant most strongly criticized. But Kant also disallows the concept that people’s happiness, or happiness of others, could be the determining grounds of will. We naturally feel pleased with others’ happiness, and even feel required to do something for them in order to bring about such happiness, but we cannot assume that every rational being experiences this kind of demand, and therefore the maxim that contains such a material and empirical condition cannot be a law30.

  1. The significance of Freedom. The concept of freedom, in the sense of autonomous lawmaking of will, is crucial to Kant's ethics, whereas Utilitarians do not address any claims of that kind.

Since the last topic (5) is beyond the scope of this article, I will examine points (1) through (4) in the remaining sections. As far as these points are concerned, the differences between Utilitarian and Kantian ethics are only superficial. To show this is the aim of the present article.

2. Fundamental Principles of Morals

As far as we literally understand the central principles of the two theories, they are simply different. However, it should be noticed here that even for Utilitarians such as Henry Sidgwick, the Utilitarian principle was actually not a fundamental principle. After examining the earlier Utilitarian arguments, Sidgwick pointed out that the Utilitarian principle is not self-evident in itself and needs further philosophical foundation if it is to be really coherent and solid. And he, by investigating our “really clear and certain ethical intuitions”31, arrived at three fundamental principles of ethics, the truth of which we will all accept if we think carefully, and which also form the basis of Utilitarianism. The term “intuition” here means our capacity to comprehend some apparent truth without using any induction or inference from experience. “Truth” refers to something universal that never becomes false without reason; every intelligent and reflective person would ideally agree upon its truth, and in that sense it can be called “objective”32. Sidgwick presents three principles as universal and objective truths, which can be comprehended by our philosophical – that is, repeatedly examined and reflected upon, and, as such, most reliable – intuitions33. Sidgwick rephrases these principles several times, but the most straightforward expressions would be these:

The Principle of Justice: “It cannot be right for A to treat B in a manner in which it would be wrong for B to treat A, merely on the ground that they are two different individuals, and without there being any difference between the natures or circumstances of the two which can be stated as a reasonable ground for difference of treatment”34.

The Principle of Rational Prudence: “Hereafter as such is to be regarded neither less nor more than Now”35.

The Principle of Rational Benevolence: “Each one is morally bound to regard the good of any other individual as much as his own, except in so far as he judges it to be less, when impartially viewed, or less certainly knowable or attainable by him”36.

Since the derivation and implications of these principles have been explicated elsewhere37, here I will just summarize what I think are the relevant points. The Principle of Justice embodies our fundamental intuition about the one formal feature of normative judgments, namely, what we all assume when we pass our judgments in which the term “right”, “ought to” or other normative words are used, whatever the judgments’ contents. We would all admit that it would be contradictory to say “A ought to stop smoking in public, but B doesn’t have to do so in the very same situation, though I cannot think of any reason which explains this difference” or “Euthanasia ought to be allowed to C in his condition and his circumstances, but not to D in a very similar situation, though there is no reason to treat these two cases differently”. This being so, the Principle of Justice requires us to treat all similar cases similarly, and not to discriminate against one particular individual in favour of another, in the application of our judgment about what ought to be done or what is the right thing to do. The Principle of Justice is also called “a formal principle of Justice or Fairness”38, for it asks us, as the formal requirement of normative judgment, to be impartial within the range of cases covered by the logic of such judgment.

A second principle is that of Rational Prudence, whose essential claim is that we should not give different weight to the same amount of goodness at different moments just because one moment is sooner and another is later – “the mere difference of priority and posteriority in time is not a reasonable ground for having more regard to the consciousness of one moment than to that of another”39. “Consciousness” here can be replaced with “goodness”, judging from the context. What is required here is not impartiality in the logical application of our judgment, but impartiality in putting values on goodness over time. Sidgwick calls this principle by the name of Rational Prudence, for the deviation from this principle is most clearly seen in the case of imprudence, in which one lacks consideration for one’s own future.

The Principle of Rational Benevolence states that, if we are to take a universal point of view, we should not give different weight to the goodness of different individuals as far as they are regarded as being of the same amount, just because they are different individuals. This is the principle which requires impartiality in putting values on goodness across different people.

According to Sidgwick, these three axioms are indispensable components of the Utilitarian principle. But it should be noticed that in these principles the notion of happiness or pleasure, which is also central to Utilitarian claims, has not yet appeared. The above principles refer to the notion of “good”, but what is good is not yet specified. “Good” means something desirable, or what one would desire if one were rational. In Sidgwick’s terminology, what is good in itself – that is, not as a means of obtaining some other good – and ought to be aimed for is called “an ultimate Good”. “The maximum ultimate Good on the whole” becomes our end we ought to aim for. In either case, good is not a synonym for pleasure or happiness. But this is not the end of the story. Sidgwick further sets out a new argument to induce us to accept the truth of Hedonism, by assuring us that there is nothing but someone’s pleasure or happiness which we could, on reflection, really regard as the ultimate Good. Then, by combining the above three principles with the claim of hedonism, Sidgwick finally establishes the Utilitarian theory that we should give equal weight to everyone’s equal happiness and aim to bring as much happiness to people as possible. For the three principles tell us to be impartial in making normative judgments as well as in evaluating the goodness of individuals at different times, and hedonism tells us to see happiness as the sole ultimate good40.

The above argument clearly assumes that the three principles and the claim of Hedonism are the very fundamental ideas underlying the Utilitarian principle. This is a quite significant fact, which may prove the close relationship between Kant and Utilitarians.

2-1 Overlaps of fundamental principles

The Universal-law formulation and the principle of Justice

To reveal the overlooked similarities of Utilitarianism and Kant’s ethics, it would be convenient to begin with the plain fact that Sidgwick himself professes that his Principle of Justice corresponds to Kant’s Fundamental Formula of Categorical Imperative, namely, the Formula of Universal Law.

I have already noticed that his [Kant's] fundamental principle of duty is the “formal” rule of “acting on a maxim that one can will to be law universal”; which, duly restricted, is an immediate practical corollary from the principle that I first noticed in the preceding section [i.e., the Principle of Justice]41.

That whatever is right for me must be right for all persons in similar circumstances which was the form in which I accepted the Kantian maxim seemed to me certainly fundamental, certainly true, and not without practical importance42.

The Principle of Justice tells us to treat similar cases similarly and not to favor some particular individual in our application of normative judgments. This implies that I should be prepared to let my normative judgment become a principle that applies equally to all individuals in similar circumstances. It is evident that from this statement follows the Fundamental Formula of the Categorical Imperative, which tells us to act according to the practical principle which each of us can will to be valid for all the people placed in similar situations – in other words, “to act according to the maxim through which I can at the same time will that it become a universal law”.

Sidgwick nevertheless points out some reservations about the validity of Kant’s claims.

For instance, Kant was wrong, Sidgwick says, when he thought he could derive all particular rules of duty from this single fundamental formula. For it is conceivable that a will that satisfies the requirement of this formula might turn out to be wrong43, as in the case of a sadistic maxim which a sadist can will to be valid for all the people in similar situations – he may be able to sincerely will his judgment that “any sadist like myself ought to torture any person in situation A” to be a universal law which applies equally to all people in like situations, including himself. Again, Sidgwick argues that Kant's argument for deriving the duty to help people in distress solely from this formula is not very cogent44. Kant tries to defend his argument by saying that we could indeed conceive it to become a universal law but we cannot will it to be such, because everyone at times needs the aid or love of others; however, whether one can avoid willing it to be such may be different from person to person. We can surely imagine a person who is so sturdy and independent as to decide not to ask the aid of others, or who reasonably judges that it would instead be advantageous for him to dispense with others help.

We may also be perplexed by another of Kant’s moves to defend his derivation of particular duties, in which he adopts the formula of Natural Law instead of that of universal law, reinterpreting the phrase “whether you can will your maxim to be a universal law” as “whether you can will your maxim to be as if it is a natural law”. In doing this, he insists not only that every particular duty has its grounds in its conformity with a natural-law-like universal principle, but also that the end which Nature seems to have given us humans is the preservation or promotion of life and so we should fulfill this end. To this notion of natural purpose I will return later.

Sidgwick also thinks that Kant's fundamental formula should be “duly restricted”, as seen in the first citation shown above. One point Sidgwick thinks Kant was missing is that “a practical principle which could apply for all the people in similar situations” need not be simple and general; it can instead be specific, contrary to what Kant expected universal laws to be. For instance, we can observe such a specific principle as “one ought not to kill any human being except in the cases of self-defense and execution” or an even more complex one adding extra exceptions and conditions, as applicable to all people placed in the same circumstances. Another point Kant does not mention is, according to Sidgwick, that there are certain principles which hold on condition that not everyone will perform the stated act. Kant, for example, tries to prohibit making a promise that one is not actually going to keep and asks people to imagine what would happen if everyone made such a fake promise; however, to consider if I can will my maxim to be a universal law is not the same as imagining what would happen if everyone did the same sort of act. One’s maxim to remain single or to lead an ascetic life are two such examples which could be thought of as valid on the premise that they will not be widely imitated by people. Though it may be impossible for us to will that everyone should decline to reproduce, we can surely will the maxim that “one may stay single while one is confident that this decision does not threaten the prosperity of humankind” to be a practical law which all people in like situations should obey45.

Nevertheless, it is obvious that what the principle of Justice and the formula of universal law require is essentially the same. Even for Sidgwick, the principle of Justice is an objectively and universally true principle, valid for all rational beings who try to reason carefully in an effort to make normative judgments. The Utilitarian principle itself is not a fundamental principle; rather, the validity of every Utilitarian moral judgment must be tested in the light of this Fundamental Principle of Justice, i.e., the Formula of Universal Law, taking into consideration the reservations posed by Sidgwick. But here Sidgwick goes on to argue that the Utilitarian principle fits well into this formula of universal law and will never collide with it, saying that

“I certainly could will it to be a universal law that men should act in such a way as to promote universal happiness [i.e., people’s happiness]; in fact it was the only law that it was perfectly clear to me that I could thus decisively will, from a universal point of view”46.

However, as Sidgwick points out, the Principle of Justice alone cannot be a sufficient guide for deciding what we ought to do, for it just states the logic-related requirement of normative judgment. And for that reason, Sidgwick presents two more fundamental principles. But here we should notice that, like Sidgwick, Kant also presents other formulae than that of universal law. This coincidence will be investigated next.

The formula of an end in itself

Sidgwick seems dissatisfied with Kant’s argument concerning the Formula of an End in Itself47. His complaint is that, even if we accept Kant’s idiosyncratic usage of the notion of “an end”, in which a rational human being is said to exist as an end in itself, and admit that we should esteem particular ends which such rational beings hold, it is still unclear why we should respect various ends that ordinary people actually seek, including ends that seem irrational, motivated by empirical desires and aversions.

However, I think we can, and perhaps should, insist that this Formula of an End in Itself contain the essential claim of Sidgwick’s Principle of Rational Benevolence. For, if the former formula indicates that we should respect a person as a subject with his own ends (which should be equally evaluated to those of mine), this formula shares essentially the same claim as the Principle of Rational Benevolence, which orders us to give equal weight to goodness, i.e., the ends, of different people. In addition, we can construe Kant’s other claim that “one must not even treat our own selves as a mere means” as indicating the precept that one should treat one’s future ends, i.e., the ends that one might possibly have in the future, as if they were one’s present ends. If we do so, that claim also encompasses the essential claim of Sidgwick’s Principle of Rational Prudence.

Let me explain in more detail. First of all, it is certain that the end in itself which Kant has in mind is something we should respect in itself and not consider as a mere means, and at the same time, we should regard it as something which generates particular ends of its own. And when he derives duties towards others by applying the Formula of an End in Itself in his Grundlegung, Kant writes “the ends of a subject who is an end in itself must as far as possible to be also my ends, if that representation is to have its full effect in me”48. In addition, it is also thought that such ends of a subject ought to be not only preserved, but also positively promoted. According to his account of the two main duties towards others – duties of love and respect for others – in his Metaphysik der Sitten, the first duty is explained as “the duty to make others’ ends my own (provided that these are not immoral),” and the second as a duty “of not exalting oneself above others”49. Now, if we can understand the idea “to make another’s ends my own and not to exalt myself above others” as equivalent to “to respect and evaluate others’ ends as having equal weight to my own ends”, and if the idealized formulation of the idea that “ends must be positively promoted” becomes the claim that “one ought to promote those ends as much as possible”, then Kant’s points will certainly constitute the claim which corresponds to the Principle of Rational Benevolence, which tells us to respect others ends (the good for others) and my own ends (the good for myself) impartially and to promote them as much as possible.

If this interpretation is correct, Kant insisted on essentially the same thing as the Principles of Prudence and Benevolence, in presenting his Formula of an End in Itself. It should be observed, however, that in any of these principles the notion of happiness has not yet appeared. The Formula of an End in Itself, construed as above, simply states that one should esteem various ends equally and promote them. Even if Kant claimed this, it does not immediately mean that he was a hedonistic Utilitarian. Still, we should remember here that the principles of Prudence and Benevolence were, for Sidgwick, two fundamental principles indispensable for constructing the Utilitarian Theory.

The Formula of Autonomy

As to the Formula of Autonomy, a brief comment will be sufficient. Kant’s formulae of universal law and an end in itself are those which every rational being should accept of his/her own free will. Likewise, Sidgwick’s three fundamental principles are presented as those which we would embrace if we underwent intellectual reflection. When a person applies the Principle of Justice to oneself, and sets the Principles of Prudence and Benevolence for oneself and obeys them, one is rightly called a rational being in Kant’s sense, that is, a being who voluntarily sets a law for oneself that holds for every rational being. Sidgwick does not mention a principle that corresponds to Kant’s Formula of Autonomy, but there seems to be no conflict between this Formula and Sidgwick’s ideas.

2-2 “Law must be the determining ground of will”

From the argument of previous section, another important point emerges. It has been argued that Utilitarianism is incompatible with Kant's ethics, because Utilitarian morality adopts the object of desire, i.e., happiness, as the sole ultimate end, and thus rests on a material determining ground of will. But the three principles Sidgwick presented – each of which does not refer to the Utilitarian principle, but all of which constitute the foundation of it – are the principles that contain no particular object of will: The Principle of Justice is a formal principle to which any normative judgment, regardless of its content, should conform. Further, the Principles of Prudence and Benevolence are characterized by the notion of good, which means the object of will, but its material content is not yet determined. Thus, these principles indicate no “material” determining ground in Kant’s sense50.

Furthermore, if we may assume that Sidgwick’s explication of Utilitarian ethics is correct, even in Utilitarianism a moral will must conform to these fundamental principles in the first place. Kant said that the determining ground of will must be laws. But also for Utilitarian ethical theory, we can say that the ultimate determining grounds of our moral will are not our personal desires, but autonomous yet universalizable rules of conduct which must conform to those fundamental principles which in turn constitute Utilitarian theory. In Utilitarian and Kantian ethics alike, a moral will and a mere desire are to be distinguished; one must go beyond one's own selfish interest and form a will which often restrains one's own desire. Such a will must be determined so as to conform to the three fundamental principles, which, I claim, are equivalent to the formulae of Categorical Imperative. Even for Utilitarianism, to conform to these three principles are prerequisite for our moral will, and logically comes prior to our estimating how much happiness such a will can bring about. In addition, Sidgwick’s three fundamental principles are stated as those which every rational being would accept as absolute necessity, so they can be rightly called objectively universal principles of morals. The Utilitarian’s ultimate determining grounds of moral will are such universally-valid fundamental principles; and, in acting morally, a person should be motivated not by his partial desire but by his own will to regulate his own act in a way in which such an act abides by those principles.

Indeed, Kant obviously has more stoic view than Utilitarians as to the incentives of moral acts. Kant says that, when one is to act truly morally, one must eliminate all influences of other incentives including sympathy and compassion, and act solely out of respect for practical law51, whereas Utilitarians often think that sympathy and compassion play some important role in making moral decisions (because, in their application of the Utilitarian theory, they have to consider others’ happiness). But it seems to me that this is nothing more than a difference regarding the question of how far we should emphasize and extend the same claim about the fundamental moral principles. Utilitarians assert that a will which is not determined by the fundamental principles cannot be called moral. They would also be able to affirm that, even though our acts appear to conform with duties, if we keep acting from our selfish inclinations or simply from naive sympathy or compassion, our respect for law will fade away; we will gradually become unaware of the importance of the three fundamental principles, and our morality will deteriorate. Such a possibility of moral deterioration is, I propose, what Kant wanted to emphasize most when he insisted that we ought not to introduce other incentives than respect for law. If this is correct, Utilitarians could claim basically the same thing, in not so strict a manner as Kant.

2-3 Fundamental principles as a priori synthetic propositions

According to Sidgwick, the three principles are self-evident, non-tautological, and significant practical principles that can be grasped by philosophical intuition52. It was suggested before (at the beginning of Ch.2 of this article) that Sidgwick’s “intuition” denotes our capacity to comprehend some apparent truth as self-evident, without the use of any induction or inference from experience53. The principles which do not derive from experience are what Kant calls a priori principles. And the non-tautological yet significant principles – i.e., the principles which have greater significance than a tautological truth, and whose truth cannot automatically be proved by a mere analysis of concepts that appear in those principles – are what Kant would call synthetic principles. Thus, Sidgwick’s three principles are a priori synthetic principles in Kant’s sense. For Kant, the validity of the fundamental laws of categorical imperatives come to us as a priori synthetic propositions; but the same is true of Utilitarianism. Sidgwick says the fundamental Principles of Justice, Prudence and Benevolence are no demonstrable truth, intuitionally comprehended as self-evident. Kant writes that the fundamental law comes to us by itself, not as an empirical fact but as the “Fact of Reason” or a priori synthetic proposition54. As you can see, Kant and Sidgwick take quite similar stands in terms of their treatment of the fundamental principles of ethics.

However, regardless of whether the principles are comprehended intuitionally or a priori, one question remains: should we really accept and act according to these fundamental principles? Neither Sidgwick nor Kant has answered the question of why we must adopt these principles; both just say that these principles are given intuitionally or a priori55. I will discuss this puzzle in the final chapter of this article. Here I confine myself to confirming the similarities between the three fundamental Principles of Utilitarianism and the Formulae of Categorical Imperative in Kant’s ethics.

In the next chapter, I will further argue that, in their attitudes towards pleasure or happiness, there is also no fundamental conflict between the two theories.

3. The ends that are also duties

The contrast between Kant’ theory and Utilitarianism is often depicted as Deontology vs. Consequentialism, but Kant never neglects consequences which we ought to expect when we make moral decisions and which we ought to aim for in conducting moral acts. In his Metaphysik der Sitten, Kant introduces the notion of “he ends that are also duties”, which a moral will ought to ultimately aim for and the realization of which we ought to bring about.

But ethics goes beyond this and provides a matter (an object of free choice), an end of pure reason which it represents as an end that is also objectively necessary, that is, an end that, as far as human beings are concerned, it is a duty to have56.

That Kant considers matter at this stage of his argument is not contradictory to his previous claim that we should not presuppose any material determining grounds of will when we seek the superior principles of morals. To adopt the fundamental principle (s) of morals in which the object of will is not specified is fairly compatible with considering what specific ends a will ought to aim for while abiding by the fundamental principles.

Kant claims that such ultimate ends are one's own perfection and the happiness of others57. Though it is commonly thought that Utilitarianism does not focus on perfecting oneself and that Utilitarians take much simpler view of the relation between happiness and the moral end, I will insist that Utilitarians take almost the same position on ultimate ends as Kant.

3-1 Overlapping contents of “the ends that are also duties”

One’s Own Perfection

Sidgwick’s own opinion about Kant’s argument of the duty-bearing ends is partly critical. He thinks that what Kant could meaningfully propose as “an end that is also a duty” refers only to the happiness of others and not to one’s own perfection. Though he is aware that “Kant no doubt gives the agent's own Perfection as another absolute end”, Sidgwick insists: “We find that when he [Kant] comes to consider the ends at which virtuous action is aimed, the only really ultimate end which he lays down is… the happiness of other men”58. Accordingly, Sidgwick makes few comments on the notion of one’s own perfection, simply charging that

when we come to examine his notion of perfection, we find that it is not really determinate without the statement of other ends of reason, for the accomplishment of which we are to perfect ourselves”59.

By cutting off half of Kant’s argument on ultimate ends in this way, Sidgwick simplifies that Kant and Utilitarians would largely agree on the ultimate end of moral acts.

However, I think Kant’s claim about one’s own perfection can be interpreted in a harmonious way with Utilitarianism. What Kant seeks in the name of one’s own perfection are the cultivation of all kinds of one’s own faculties or natural predispositions needed to promote one’s reasonable ends, and the cultivation of one’s will or morality. What Kant suggests here is that one needs to cultivate certain abilities and physical/mental conditions in order to make moral decisions and fulfill them, so we ought to equip ourselves with those abilities and conditions as far as moral duties are to be fulfilled. Thus he says that it is our duty to encourage ourselves to become capable of setting ends independently and performing acts that serve our ends; and, for these purposes, to supplement our ignorance by instruction, to correct our errors, to cherish one’s own nature, but at the same time to become capable of acting confidently and rationally without being distracted by our inclinations60. If this understanding is correct, then, Utilitarians would have to regard one's perfection as what they ought to promote. Whatever the contents of moral duties, one must cultivate intellect and willpower in order to be able to make well-reasoned moral decisions and carry out what one has decided. One must also be equipped with certain physical and mental abilities to fulfill his duties. Whatever the particular duties are, one’s own perfection in the above sense can properly be called “an end that is also a duty”, for in order to make a moral judgment and carry it out we must impose the task of cultivating ourselves. But this duty is simply a logical necessity which arises when one tries to make and carry out moral judgments, so it is almost taken for granted by Utilitarians, who have not explained much about the conception of one's own perfection.

Happiness of Others

Another end that Kant mentions as also a duty is others happiness. He explains happiness as “satisfaction with one’s state, so long as one is assured of its lasting”61, which is not peculiarly different from the Utilitarian definition of happiness or pleasure. But Kant insists that since every human inevitably seeks their own happiness, an end which one has a duty to promote is not one's own happiness, but the happiness of other human beings62. Kant also points out that “it is for them [other people] to decide what they count as belonging to their happiness” and “I cannot do good to anyone in accordance with my concepts of happiness… rather, I can benefit him only in accordance with his concepts of happiness”63. Kant’s idea of promoting others happiness from their point of view corresponds to another important point Sidgwick suggested regarding Hedonism, i.e., that an individual’s happiness must be understood as what the very individual who is feeling it would explicitly or implicitly comprehend as desirable64.

It might be objected that, unlike Utilitarians, Kant clearly denies that we have a duty to promote any happiness of others, and states, “but it is open to me to refuse them many things that they think will make them happy but that I do not, as long as they have no right to demand them from me as what is theirs”65. However, Sidgwick, who defends Utilitarianism, similarly argues that another human being’s happiness that should be taken into moral consideration must be understood not simply as satisfaction of that being’s actual desires (for one quite often desires what would lead him/her to unhappiness in the long run), but rather as what can also be regarded as a rational end for that being66. Thus, Utilitarian and Kantian ethics are similar here again, in that another individual's happiness that should be taken into moral consideration must be what the individual in question would reasonably desire, instead of what he actually desires now.

Nevertheless, the two theories appear to differ in the treatment of one’s own happiness. According to Kant, we cannot regard seeking one’s own happiness as a compulsory duty, since one inevitably seeks it. It could be one's indirect duty to attend to one’s own happiness, but that is partly because what is generally called happiness, including health and wealth, often serves as a means to fulfill one’s duties, and partly because an unhappy state such as poverty tends to induce us to breach our duties67. The third reason to include one’s own happiness as one’s duty is that, in Kant’s opinion, as a universal law set by Reason, the duty to promote happiness should have “all human beings (including myself)” instead of “all others except myself” as its proper object68. This last reason is an unambitious claim that simply allows one to seek one’s own happiness in order to accommodate our duty of benevolence to the Formula of Universal Law. The first claim is also a humble one that admits one’s duty to promote one's own happiness only as a means to other moral ends. By contrast, Sidgwick agrees with Butler that “one’s own happiness is a manifest obligation independently of one’s relation to other men”69. The main reason he insists this is that, though Kant says everyone inevitably seeks their own happiness, we would all admit that one does not inevitably seek to bring about what one believes to be one’s own maximum happiness in the long run70. In being tempted by an immediate benefit, an individual sometimes fails to do what would bring more overall happiness for himself. Sidgwick insists that it is one’s duty to promote one’s own overall happiness, considering one’s future self as well as present self.

From the above discussion of Sidgwick and Kant’s treatment of an individual’s happiness, there appears to be one discrepancy between the two ethical theories. However, if we look at their claims carefully, we will find that this disagreement comes not from the difference in their central claims about the nature of morality, but rather from the difference in their view of an empirical question about whether one “inevitably” seeks one’s own happiness. Though Kant claimed that a human being inevitably aims for his or her own happiness, if he had thought of whether a human inevitably seeks his/her own overall happiness he would have answered in the negative. If he had conceded our tendency to neglect our own long-term happiness, he would have been forced to agree with Sidgwick that considering one’s own overall happiness is also a duty, for the very reason Kant himself presented when he claimed that one’s own happiness should not be regarded as duty because one inevitably seeks one’s own happiness; if it turns out that one does not inevitably seek it, then one’s own happiness can be one’s duty.

At any rate, Kant regards the happiness of human beings in general as an end we ought to promote. This claim, that happiness of others as well as oneself is the ultimate end of our moral duties, is, needless to say, what is consistently advocated by Utilitarians.

3-2 “Happiness cannot be the direct determining grounds of will”

At this point one might argue that Kant contradicts himself because his claim that we ought to seek people’s happiness seems to conflict with his other allegation that we should not make happiness – whether one’s own happiness or people’s overall happiness – the determining grounds of our will. But Kant is consistent here. The ultimate incentives of our moral decision-making should not be our spontaneous yet uncontrolled inclinations to pursue happiness, but our reflective resolution to autonomously regulate our acts. That is what Kant meant when he claimed that the determining grounds of will must be practical laws. Still, in asking what such laws should ultimately aim for, Kant argues that other people’s happiness must be an ultimate end for which our moral will ought to aim.

But, if Kant is consistent in his explanation of the relationship between happiness and will, so is Utilitarianism. Utilitarianism similarly argues that moral acts should be done out of our own principled resolution that conforms with the three fundamental principles; yet Utilitarians go further and ask what ultimate ends such resolution should aim for, then reach the conclusion that happiness must be the ultimate end of our moral will.

It should be noticed here that Sidgwick’s “Hedonism about ultimate good” is a claim not about the end we do aim for (i.e., what we actually desire), but about the end we ought to ultimately aim for (i.e., what we consider to be desirable on reflection). Sidgwick argues that the normative claim “happiness is the sole ultimate good which we ought to aim for” cannot be derived from the empirical claim that everyone is actually seeking happiness, because, for one thing, everyone does not always consciously desire happiness; we sometimes desire other things than happiness such as ideals, truth, discipline and even self-sacrifice or suicide. For another thing, even if we admit that we do seek happiness generally, it does not immediately follow that we ought to aim for it. According to Sidgwick, Utilitarianism says our moral will must not be determined by the empirical fact that we do seek happiness. Our moral will has its root in our principle-oriented rationality, which is distinguished from our desire for happiness. But after confirming this, Sidgwick raises an entirely new question of what our moral will ought to aim at. Then he examines every conceivable candidate for the ultimate end of moral will, e.g., virtuous acts, the preservation of life, truth, beauty, etc., and by eliminating each, finally comes to the conclusion that the sole ultimate end we ought to aim for is happiness, whether one’s own or someone else’s71. Now, remember that Kant argued that the conceptions of good and bad come not prior to but after the moral laws, and must be determined by those laws. But Sidgwick also argues that the concept of Good or the end that ought to be aimed for come in the same order, after the presentation of the fundamental principles of ethics. If both Kantian and Utilitarian ethics similarly summarize the ends one should aim for as “people’s happiness” and “the cultivation of one’s ability to form moral wills and to fulfill them”, in either theory our moral decisions will be based on which act (or maxim of act) will most possibly have the consequences of fulfilling these ends. This consequentialism is what both Utilitarians and Kantians advocate. A simple dichotomy such as “consequentialist Utilitarians vs. deontologist Kant” or “hedonistic Utilitarianism vs. anti-hedonistic Kantianism” is misguided. Both theories intend to claim essentially the same thing. They merely differ in their ways of emphasizing some points.

3-3 Ethical Hedonism as an a priori synthetic proposition

Let us see the similarity between the two ethical theories in their treatment of happiness from another perspective. Sidgwick presents ethical hedonism as an intuitive claim. According to him, the validity of the claim that happiness is our sole ultimate end cannot be proved by an empirical (but actually false) claim that we always seek happiness. Nor can its validity be proved by any logical inferences from the fundamental principles of morals. The only thing Sidgwick could do was to examine every possibility in his pursuit of what is the ultimate good, and, by using intuition, to propose (not prove) happiness as the sole remaining candidate72. For Sidgwick, hedonism is a true but undemonstrable intuitive claim.

But how does Kant establish his claim that the happiness of others is an end that is also a duty? In some places Kant seemingly tries to prove that our duty to promote others’ happiness can be deduced immediately from the Fundamental Formula of Categorical Imperative. He argues that we cannot will the maxim that anyone in distress ought to be left alone without being helped to become a universal law, since everyone at times needs the love and help of others73. But Sidgwick does not regard Kant’s argument as convincing. For Sidgwick argues that it is an empirical proposition and not universally true that anyone in distress would seek another’s assistance74.

Instead, Sidgwick insists Kant is actually assuming that promoting others happiness is a self-evident, a priori duty75. This is not an extraordinary claim, for Kant in fact states as follows:

 … For since the sensible inclinations of human beings tempt them to ends (the matter of choice) that can be contrary to duty, lawgiving reason can in turn check their influence only by a moral end set up against the ends of inclination, an end that must therefore be given a priori, independently of inclinations76.

Here Kant indicates that the answer to the question of what is the ultimate end of moral will comes to us a priori, as if it is an intuitively-apprehended truth. If so, Kant's claim that others happiness is an ultimate moral end is also an a priori claim which is intuitively known to be true. In addition, both Sidgwick and Kant believe that the notion of good cannot be reduced to the notion of happiness, i.e., that happiness is the sole ultimate good is not an analytical truth, but a synthetic truth. Therefore, the claim that happiness is an ultimate end of moral will is, again, an a priori synthetic claim in Kant’s sense, or in Sidgwick’s terms, an intuitively self-evident yet significant claim. Here we can see the clear similarities in their attitudes towards ethical Hedonism. Nevertheless, as in the case of the fundamental principles, we will notice a question remaining here: why should we aim for others happiness? Both Sidgwick and Kant say the reason can be intuitively known, but what is the point of their claim that promoting others happiness is a self-evident moral duty? I will return to this puzzle shortly.

So far then, we have found no conflict between the contents and nature of the fundamental principles of Utilitarian and Kantian ethics. The same is true of their treatment of happiness. Now, what will happen if we combine these elements together?

If Kant’s formula of an end in itself (and his argument relating to this formula) can be interpreted as the requirement that we count everyone as one and respect their ends as having equal weight to our own, and if Kant’s claim that an end should be positively promoted can be ideally restated that an end ought to be promoted as much as possible, then Kantians may well come to find the Utilitarian theory quite as plausible as theirs; for Utilitarians just combine these claims and propose that, when people’s ends conflict with each other, one ought to respect their ends impartially (that is, treat them as if they are one’s own ends) and endeavor to fulfill those ends as much as possible from the overall point of view, while giving weight to each end in proportion to the strength of each person’s willingness to attain his or her end. Furthermore, even the hedonistic version of Utilitarianism could become plausible for Kantians, if Utilitarianism and Kantianism can both agree that the ultimate ends that one morally ought to aim for are nothing other than promoting the happiness of others as well as one’s future self, in addition to cultivating one’s own faculties and willpower to form and fulfill moral decisions.

By combining the above claims regarding fundamental principles and ultimate ends in this way, we can see the strongest link between Utilitarian and Kantian ethics. However, at the same time we can see one main reason why the Utilitarian and Kantian ways of moral thinking eventually differ a great deal. I said in the last paragraph that Utilitarians simply combined their fundamental ideas. If Sidgwick is correct, Utilitarianism is a theory which combined those fundamental ideas systematically and constructed a single Utilitarian principle, namely, the Greatest Happiness Principle, which can be used for practical applications. But Kant didn’t do so – he never combined the idea of the supreme principles with that of the ultimate ends; he kept those claims apart, presenting each as having independent importance. This difference in the methodology of theory-constructing makes the seemingly huge distinction between the two theories. Since Kant presented his Formulae of Categorical Imperatives and his moral ends separately throughout his entire argument, he always tried to apply each principle or end singly in judging particular duties in given situations. And when he faces the question of what one ought to do when two duties conflict, Kant says that “the stronger ground of obligation prevails (fortior obligandi ratio vincit)”77; but to judge which duty weighs more, Kant would take separate steps, applying the Formulae of the Categorical Imperative one by one, and/or asking if performing one or the other duty would better fulfill one or the other end that is also a duty. Since (for Kant) these steps cannot be integrated into one single procedure, what particular duties we have in each case cannot be decided in a linear way; therefore Kant presented what he termed Casuistical questions to consider particular cases, in which one examines what one ought to do from various perspectives instead of providing one decisive answer. Kant thought of Casuistry not as a science but a training in judgment, which cannot be explained in a systematic way but only “woven into ethics in a fragmentary way”78. So, Kant thought that one cannot systematize how to deal with practical questions; however, the Utilitarians focused on the very procedure for doing so. Utilitarianism, which establishes one single principle combining three Fundamental Principles with hedonism, seeks to provide one conclusive answer to the question of what one ought to do in a particular case by applying this handy principle together with some devices for estimating and comparing the weight of people’s happiness. For this reason, the ways Utilitarians and Kantians discuss practical topics come to differ greatly. But it should still be remembered that the two theories share the very same fundamental principles and claims at the core of their theories.

However, my claim may be biased regarding the derivability of a Utilitarian claim from Kant’s formulae combined with his “ends that are also duties”, in arbitrarily interpreting the Formula of an End in Itself and the contents of ends that ought to be aimed for. To be a Utilitarian, one must be able to claim that the moral end that ought to be aimed for is people’s happiness and happiness only (except for the end of cultivating one’s own faculties and willpower to fulfill moral ends). But I am not certain whether Kant would have agreed. How to interpret the notion of “the natural end” that Kant often mentions, for instance, would be relevant to this question. If Kant introduced his notion of the natural end as what we ought to aim for besides the cultivation of our own faculties to fulfill our duties and the promotion of happiness, we cannot establish the complete link between Utilitarian and Kantian ethics. The interpretation of the natural end is another possible opposing point of the two ethical theories. Whether it yields a serious conflict between Utilitarian and Kantian ethics will depend on how we interpret Kant’s teleology.

There is one more possible opposing point between Kant and many Utilitarians. Through the long history of Utilitarianism, not a few Utilitarians have insisted that we ought to promote the happiness of any sentient beings, taking non-human animals as well as humans into moral considerations. But Kant argues that “as far as reason alone can judge, a human being has duties only to human beings”79. Kant says this because, according to him, a human’s duty to any subject is moral constraint by that subject’s will, and as far as we know, only a human can be such a subject, having a will and being capable of imposing constraints on other beings. Still, I wonder if this difference in practical opinions really comes from the discrepancies between the intrinsic natures of the two theories. It is conceivable that some Utilitarians take positions similar to Kant’s, claiming that morality is nothing but a kind of mutual system, or reciprocity, among human beings who can communicate with each other. This point relates to a broad question about the meaning of morality, or our moral life, rather than a question of the internal structure of particular normative theories such as Utilitarianism and Kantianism.

Now, though there may remain some possible opposing points between Utilitarian and Kantian ethics, I have provided enough evidence to show how we can dismiss as groundless most of the so-called discrepancies between them. To complete the discussion of the relationship between the two ethical theories, we still must deal with Kant’s argument about Freedom. A major discrepancy finally appears between Utilitarian and Kantian ethics in their treatment of freedom. Since such a discussion requires detailed investigation, I prefer to take another opportunity to explore this topic.

4. A short remark on the validity of central claims

Before concluding this paper, it will be desirable to discuss one remaining puzzle, that is, the question of why Kant and Sidgwick both insist that the fundamental principles of ethics and the ends that ought to be aimed for come to us as a priori synthetic, or intuitively self-evident, truths. According to both, one can comprehend these truths by one’s own philosophical intuition, or Reason.

When we discuss ethics, to justify one’s own argument by saying that “it is intuitively self-evident” or “it is dictated as the Fact of Reason” is in most cases inappropriate, for that line of argument has no convincing power for those who do not share that intuition or that Fact of Reason. Though I generally admit this kind of inappropriateness, I am exceptionally inclined to think that Kant and Sidgwick’s claims about the fundamental principles and the ultimate ends would be appreciated and accepted as the valid basis of ethics by almost all people, at least on reflection. But the reasons for accepting those principles and ends may be different from person to person. Kant and Sidgwick adopted them because they thought of those principles and ends as intuitively true, or because they found themselves already accepting them as “the Fact of Reason”. Likewise many people might accept those principles and ends as intuitionally self-evident, but some may accept them solely from a selfish point of view, thinking that “I honestly want to utilize others for my own ends, but in order to do so I must appear to be a nice and reliable person, treating myself and others equally, at least in public”. Benevolent individuals may appeal to our sympathy for others, in contrast with intuition or selfish motives, to convince us of the value of treating others equally. Some philosophers have analyzed the logic of moral judgment, or examined what psychology or evolutionary theory tells us about the nature of morality to explain the reason to accept those principles and ends. There is, in short, no single reason that can convince everyone of the meaning of an ethical life. But this very point, I think, is exactly what Kant and Sidgwick suggested in saying that those principles and ends are intuitionally self-evident; they were rightly aware that we cannot give the one and only reason for accepting those principles and ends, nor is it necessary for us to do so. So they simply ascertained that we would all admit these fundamental principles and ultimate ends for some reason or other, and left open the question of why we ought to adopt them (I do not mean they actually expressed such claims, but Kant and Sidgwick’s arguments make full sense by interpreting them in this way). One may object to Kant’s Reason or to Sidgwick’s intuition as the basis for their fundamental principles, but as far as he/she uses another reason to accept them, one cannot reject the principles themselves. Whatever the individual reason to accept these fundamental principles of ethics, if we all concede their validity, from that starting-point we can set out moral arguments80.


The apparent large gap between Utilitarian and Kantian ethics is rooted in their different ways of constructing a theory from very similar ideas: Kant, on the one hand, confined himself to presenting his fundamental claims separately, whereas Utilitarians combined the same fundamental claims and presented one single Utilitarian principle as a guiding tool for making practical decisions. In addition, another difference between Kantian and Utilitarian ethics may be based on how we interpret Kant’s notion of natural ends, which may be slightly different from what he described as the obligatory ends of morality, one's own perfection and others happiness. Whether we regard these two differences as crucial opposing points, and if we do, whose side we tend to take, will condition our ways of debating ethical issues.

It is important to clarify the exact relationship between Utilitarian and Kantian ethics before we decide which of them is the “valid” ethical theory. When Kantians and Utilitarians debate, what they should do is neither to ignore each other by assuming that each is simply different, nor to criticize each other without pondering whether they are really opposed. They should articulate their real opposing points, evaluate the other’s underlying assumptions, and argue only about their truly significant differences. They should also consider the meaning of the fundamental claims both theories have in common. A constructive dialogue between Utilitarian and Kantian ethics will start from there.

1 See R. Bennett, C. A. Erin, J. Harris and S. Holm, “Bioethics, Genethics and Medical Ethics” and G. Enderle, “Business Ethics”, in The Blackwell Companion to Philosophy, 2nd ed., edited by Bunnin and Tsui-James, Oxford, Blackwell, 2003, pp. 499-530, 531-51 (see particularly pp. 500, 546) as an example from some prevailing book of ethics. Both mention Kantian ethics and utilitarianism (or preference consequentialism, of which Utilitarianism is the most familiar version) as two of the major approaches to practical issues, though they suggest that these two theories are often too simplified or not sufficiently explored in the field of applied ethics.

2 See the Royal Prussian Academy of Sciences edition, vol. IV, pp.387-463 for Grundlegung zur Metaphysik der Sitten; vol.V, pp.3-163 for Kritik der praktischen Vernunft; and vol.VI, pp.205-493 for Metaphysik der Sitten. (Hereafter the volume/page numbers of Kant’s writings always refer to this Academy edition, except in the case of Kritik der reinen Vernunft, which will be cited by original page numbers of the first and the second edition, i.e., by the standard A/B page numbers. I also used M. J. Gregor, Practical Philosophy -- Immanuel Kant, Cambridge, Cambridge University Press, 1996 as the English translation of Kant’s writings. ) These three writings of Kant are what Sidgwick frequently refers to in his Methods of Ethics. As for Kant’s Metaphysik der Sitten, Sidgwick exclusively focuses on Kant’s argument on Virtue, or ethics and morality in a narrower sense (instead of Kant’s theory on Right, or legality), because what Sidgwick considers as the scope of ethics corresponds to that part of Kant's argument. The same is true of R. M. Hare, “Could Kant Have Been an Utilitarian?”, in Sorting Out Ethics, Oxford, Oxford University Press, 1997, pp. 147-65. See also Kant, Metaphysik der Sitten vol. VI, pp. 211-28 and pp. 375-493.

3 See John Rawls, A Theory of Justice, Cambridge, Harvard University Press, 1971, p. 22.

4 John Skorupski, “Ethics,” in The Blackwell Companion to Philosophy edited by Bunin and Tsui-James, 2003, pp. 202-230, also makes a comparison between Utilitarianism and Kantianism, claiming that these two are similar in that both acknowledge impartiality, or fairness, as a categorical ethical principle and believe that “there are principles of practical reason that are categorical but not merely formal.” But I will further articulate what kind of impartial principles they similarly hold, and at what point they start to differ. Moreover, I would rather compare Kantianism with classical utilitarianism instead of what Skroupski calls “generic utilitarianism,” which allows various interpretation of the notion of well-being and distributive principles.

5 See R. Norman, Moral Philosophers, 2nd ed., Oxford, Oxford University Press, 1998, pp. 84-5.

6 See The Encyclopedia of Kant, in Japanese, edited by K. Arifuku and M. Sakabe, Koubun-dou, 1997.

7 See John Stuart Mill, Utilitarianism, ch. 5, 1861.

8 See W. Kuroda, Acts and Norms, in Japanese, Keiso Shobo, 1992, pp. 127-8.

9 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 427. Italics as in the original text.

10 See I. Kant, Kritik der Urteilskraft, vol.V, p.353. See also his Kritik der reinen Vernunft, 1st ed., pp. 571-2 ; 2nd ed., pp. 599-600.

11 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 414.

12 See I. Kant, Kritik der praktischen Vernunft, vol. V, p. 19.

13 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 414 and p. 421 (footnote).

14 See I. Kant, Kritik der praktischen Vernunft, vol. V, pp. 19-31.

15 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 389; Kritique der praktischen Vernunft, vol. V, p. 12.

16 See I. Kant, Kritik der praktischen Vernunft, vol. V, p. 21, Theorem I.

17 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 421.

18 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 429.

19 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 431.

20 There are several ways to classify Kant’s formulations of the Categorical Imperative. See, for example, H. J. Paton, The Categorical Imperative, A Study in Kant’s Moral Philosophy, New York, Harper, 1947, pp.129-98 ; M. J. Gregor, Practical Philosophy – Immanuel Kant, Cambridge, Cambridge University Press, 1996, pp.xxiii-xxiv. But the simplest classification would be the one shown above. Some often mention other formulae, the Formula of the Universal Law of Nature and the Formula of the Kingdom of Ends, but it seems to me that Kant states the former as a supplementary explanation of the Formula of the Universal Law, and the latter as a natural result of combining the Formula of an End in Itself and that of Autonomy.

21 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 389.

22 See I. Kant, Kritik der practischen Vermunft, vol. V, pp. 71-2.

23 See I. Kant, Kritik der practischen Vermunft, vol. V, p. 130.

24 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, pp. 446-7; Kritik der practischen Vermunft, vol. V, p. 33; Metaphysik der Sitten, vol. VI, pp. 213-14.

25 See I. Kant, Kritik der practischen Vermunft, vol. V, p. 4 (footnote).

26 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 448.

27 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 401.

28 See I. Kant Kritik der practischen Vermunft, vol. V, pp. 62-3.

29 See I. Kant Kritik der practischen Vermunft, vol.V, pp. 21-6, 28, 35ff.

30 See I. Kant Kritik der practischen Vermunft, vol.V, p. 34.

31 See Henry Sidgwick, The Methods of Ethics, 7th ed., London, Macmillan, 1907, 1962, p. 387.

32 See M. Nakano-Okuno, Sidgwick and the Contemporary Utilitarianism, in Japanese, Keiso Shobo, 1999, pp. 54-5; see also Henry Sidgwick, The Methods of Ethics, pp. 341, 399.

33 See Henry Sidgwick, The Methods of Ethics, pp. 379-84.

34 See Henry Sidgwick, The Methods of Ethics, p.380.

35 See Henry Sidgwick, op. cit., p. 381.

36 See Henry Sidgwick, op. cit., p. 382.

37 See M.Nakano-Okuno, Sidgwick and the Contemporary Utilitarianism, pp. 115-35.

38 See Henry Sidgwick, op. cit., p. 391.

39 See Henry Sidgwick, op. cit., p. 381.

40 See M. Nakano-Okuno, Sidgwick and the Contemporary Utilitarianism, pp. 144-85.

41 See Henry Sidgwick, The Methods of Ethics, pp. 385-6.

42 See Henry Sidgwick, op.cit., p. xvii. Preface to the 6th ed.

43 See Henry Sidgwick, op.cit., pp. 209-10.

44 See Henry Sidgwick, op.cit., p. 389 (note); see also I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 423.

45 See Henry Sidgwick, op.cit., pp. 210 (footnote), 485ff. See also pp.318-19.

46 See Henry Sidgwick, op.cit., p. xx.

47 See Henry Sidgwick, op.cit., pp. 389-90(note).

48 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 430.

49 See I. Kant, Metaphysik der Sitten, vol. VI, pp. 449-50.

50 See M. Nakano-Okuno, Sidgwick and the Contemporary Utilitarianism, p. 230. I once claimed that Sidgwick’s three principles have “substantial content”. By “substantial content” I meant that these principles are richer than their mere tautological analytical truths. I do not mean that these principles have material content in Kant’s sense.

51 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 400. See also I. Kant, Kritik der practischen Vermunft, vol. V, pp. 71-86.

52 See Henry Sidgwick, op. cit., pp. 374-5, 379.

53 Kant also uses the term Intuition in his writings, but its meaning is quite different from Sidgwick’s use of the term. Their different usages of these words should not be confused.

54 See I. Kant, Kritique der practischen Vermunft, vol. V, p. 31.

55 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, pp. 444-5.

56 See I. Kant, Metaphysik der Sitten, vol. VI, p. 380.

57 See I. Kant, Metaphysik der Sitten, vol. VI, p. 385.

58 See Henry Sidgwick, op. cit., p. 386.

59 See Henry Sidgwick, op. cit., p. 386 (footnote).

60 See I. Kant, Metaphysik der Sitten, vol. VI, pp. 387, 391-3, 420.

61 See I. Kant, Metaphysik der Sitten, vol. VI, p. 387.

62 See I. Kant, Metaphysik der Sitten, vol. VI, p. 388.

63 See I. Kant, Metaphysik der Sitten, vol. VI, pp. 388, 454.

64 See Henry Sidgwick, op. cit., pp. 127-8, 131, 398.

65 See I. Kant, Metaphysik der Sitten, vol. VI, p. 388.

66 See Henry Sidgwick, op. cit., p. 239.

67 See I. Kant, Kritik der practischen Vermunft, vol. V, p. 93. See also I. Kant, Metaphysik der Sitten, vol. VI, p. 388.

68 See I. Kant, Metaphysik der Sitten, vol. VI, p. 451.

69 See Henry Sidgwick, op. cit., p. 386.

70 See Henry Sidgwick, op. cit., pp. 36, 327 (footnote).

71 See M. Nakano-Okuno, Sidgwick and the Contemporary Utilitarianism, p. 155ff.

72 See Henry Sidgwick, op. cit., p. 98.

73 See I. Kant, Grundlegung zur Metaphysik der Sitten, vol. IV, p. 423. See also I. Kant, Metaphysik der Sitten, vol. VI, pp. 393, 451, 453.

74 Henry Sidgwick, op.cit., p. 389 (note).

75 Henry Sidgwick, op.cit., p. 386.

76 See I. Kant, Metaphysik der Sitten, vol. VI, pp. 380-381. Italics by Nakano-Okuno.

77 See I. Kant, Metaphysik der Sitten, vol. VI, p. 224.

78 See I. Kant, Metaphysik der Sitten, vol. VI, pp. 411, 483-4.

79 See I. Kant, Metaphysik der Sitten, vol. VI, p. 442.

80 At present, I do not believe myself that the fundamental (or supreme) principles of ethics must be something that every rational being would accept without exception. Finding fundamental ethical principles that most ordinarily rational people would endorse would be sufficient to construct an ethical theory useful in dealing with practical controversies in the actual world.

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