I. Moral health and the duty to oneself in the Doctrine of Virtue.
In the last paragraph of his Doctrine of Virtue in the Metaphysics of Morals, Kant states that there „is a kind of regimen for keeping a human being healthy“ [7, Bd. 6. 485], [8, 597]. This conception seems to involve the figure of ethics as a universal medicine („Universalmedizin“). Health, in this sense, as Kant qualifies his claim, means only a negative kind of well-being that in itself cannot be felt by the subject [7, Bd. 6. 458.2-3], [8, 576]. What must be added is cheerfulness as a moral quality. As an example Kant mentions the „ever-cheerful heart, according to the idea of the virtuous Epicurus“ [7, Bd. 6. 485.3-5], [8, 597].This cheerfulness is an expression of the consciousness never to have violated deliberately one’s duty. It results from moral training, or from what Kant calls „ethical gymnastics“[7, Bd. 6. 485.19], [8, 598] which he reduces to the asceticism of the Stoics [7, Bd. 6. 477 (§ 49)], [8, 591]. These exercises are a means or even a weapon for fighting against those natural instincts that could come into conflict with morality. The aim of this fight is to master one’s emotions and passions, and furthermore, to gain a free facility in action that does not result from habitually repeated experiences [7, Bd. 6. 407], [8, 535]. At last, the aim is to reach „the state of health in the moral life“[7, Bd. 6. 409], [8, 536]. This will be a state not only free from emotions (affects), in order to set the feeling into quiet (moral apathy) [7, Bd. 6. 408], [8, 536], but consisting in the effort to put the virtuous law into practice by a „considered and firm resolution“.
The device of the Stoics esteemed by Kant, i.e. sustine et abstine (endure and abstain; in the longer version: „accustom yourself to put up with the misfortunes of life that may happen and to do without its superfluous pleasures“[7, Bd. 6. 484], [8, 597]), is exactly the principle or rule for exercises to prevent illness, that is, especially, moral sickness in order to gain a brave and happy feeling, in other words, a healthy soul. How does this principle work, and what are the conditions of its practical realization?
Sustine et abstine are qualified as moral duties but in the negative and restrictive sense as duties of omission [7, Bd. 6. 419 (§ 4)], [8, 545]. This determination follows from Kant’s objective classification of the duties according to a formal and a material aspect. Negative duties to oneself are a topic of moral health because they forbid the moral subject to act against the purpose of his own nature which is to move from brutal animal life to virtuous perfection by cultivating his faculties. What they obtain is the moral self-preservation, that means, the preservation of man’s nature in perfection. If he acts against his nature, he will get ill and feel pain. The origin of this pain lies in a moral cause, though, the effect is physical.
The first of the two principles of duties to oneself relates to moral health; it claims: „live in conformity with nature“, that is, „preserve yourself in the perfection of your nature“[7, Bd. 6. 419], [8, 545]. Perfection is to be understood here in a formal sense of quality. It is a topic involved in teleology. According to teleological reflection a thing will be perfect if its qualities are in the harmony that constitutes a purpose [7, Bd. 6. 386], [8, 518]. This purpose is a duty in itself insofar as perfection is related to man in general, in a difference to animals (cf. [7, Bd. 6. 391 f.], [8, 522 f.]). The duty, then, involves the task to civilize man’s own nature, that is, the faculty of understanding, and the faculty of his own will, in order to reach an intrinsic morally practical perfection. To do so is not only an advice by technically practical reason but also a demand by morally practical reason.
In order to avoid an antinomy between the obligating self and the one that is obliged, a duty to oneself may not be addressed to the subject as a natural being, but only as a being that has practical reason and inner freedom, and, therefore, qualifies for personality [7, Bd. 6. 418 (§ 3)], [8, 544]. There is no obligation in human activity with regard to the determination by theoretical reason, and, especially, there is no duty to one’s own body [7, Bd. 6. 419 (§ 4)], [8, 544].
The inner freedom includes, first, to be one’s own master in a given practical case by restraining one’s affects, and, second, to have the dominion over oneself by controlling one’s passions [7, Bd. 6. 407] (Remark), [8, 535]. Whereas the first element of intrinsic freedom has the negative character of a prohibition (namely, not to allow to be dominated by one’s feelings and affections), the second is an affirmative commandment (that is, to submit one’s faculties and affections altogether to practical reason).
There must be distinguished between formal and material conditions of moral duties. One of the formal conditions is that duties are grounded on moral laws that determine the maxims of action, although, these maxims have to be of one’s own free choice, that is, ethical maxims, unlike technical ones, cannot be grounded on habit. The only material condition is that duties must be coupled with purposes. What does this mean?
According to Kant, duties will qualify for duties of virtue only if they are simultaneously purposes; respectively, only those purposes are peculiar to ethics which are duties. Because the moral law that forces the moral agent to act according to maxims is the categorical imperative, and, therefore, is without special purposive content, there would be no free human activity if the maxims had no purposes produced by the subject. Different subjective aims must be related to the maxims; then the moral law demands to subordinate these aims to an objective purpose created by the subject as well; in other words, the moral law demands the subject to choose such purposes for his maxims that can be in conformity with objective purposes. If he meets this demand his maxims will be in harmony with a general legislation. This is the condition of free acting according to the moral law. In this way, the law that governs the maxims is founded only on the concept of a purpose as a duty.
II. The dispute with Hufeland about dietetics in the Conflict of the Faculties
In his reply in the third part of the Conflict of the Faculties to Hufeland’s claim that man’s physical preservation and the prolongation of his life have their foundation and necessary presupposition in moral laws, Kant states that „morally practical philosophy also provides a panacea which, though it is certainly not the complete answer to every problem, must still be an ingredient in every prescription.“ [7, Bd. 7. 98], [9, 313]
There are some parallels to dietetics in the doctrine of virtue, especially, the reference to the Stoics‘ principle, sustine et abstine, as a principle of regimen [7, Bd. 7. 100], [9, 316]. Is, therefore, Kant’s dietetical cure a cure to himself in the moral sense of self-obligation following from the concept of duty to oneself? I want to argue that, despite of these obvious similarities, the determination and the reasoning of the regimen Kant gives to the reader in the Conflict of the Faculties are different from those he offers in the Doctrine of Virtue. Moreover, he does not agree with Hufeland’s claim for moral laws as a foundation of the regimen. I have three arguments to support this view.
The first argument is taken from the role of the principle of the regimen in the Conflict of the Faculties [7, Bd. 7. 100], [9, 316]. To place Stoicism in the science of medicine Kant relies on the constitution of the living force (vital energy). Living force is a faculty of the soul relating to physiology (as a nature of animal matter) [7, Bd. 13. 398 f], (cf. [5, 453-480]), in other words, of the sensitiveness of the nerves. Its enhancement depends on activities and exercises directed to the organism. Such exercises, as Kant points out, are helpful to find the appropriate way and measure for warmth, sleep and care. But these qualities belong to the welfare of the body, although they affect naturally the soul. Moral duties, however, cannot refer to bodies. Hence, the principle of regimen used in the Conflict of the Faculties is not a principle of practical philosophy.
The second argument relates to the character of the dietetical instructions Kant uses in the Conflict of the Faculties. Although, they are resolutions which have their source in one’s own will they are technically practical rules, not maxims governed by moral legislation (cf. [1, 35]. Dietetics is a free art to avoid or to avert illness [1, 35], (cf. [7, 23, 464]). According to Kant’s division of philosophy into two domains in the Critique of Judgment (Introduction, section I) [11, 59-61], technically practical propositions belong to natural philosophy which is subordinated to concepts of nature, not, like practical philosophy, to the concept of freedom. For that reason Kant’s rules of regimen do not consist with duties to oneself.
The third argument implies the consideration that the morbid feelings that should be averted by the regimen proceed from bodily diseases. They are sensuous feelings having physical, not moral causes. Feeling cold, e. g., is not a moral vice like drunkenness. Thus, the dietetical rules and exercises are intended to improve the constitution of animal nature.
III. The double sense of dietetics: morally practical and technically practical principles
My conclusion drawn from the considerations in the preceding chapters is that Kant makes use of two different concepts of dietetics, one that is a matter of technically practical reason, and another that is part of the domain of morally practical reason. The first is directed to purposes dependent on nature, the second, however, pursues purposes independent from nature. The last ones are purposes that are also determined as duties. Their peculiar character is that they are ends in themselves because they are a priori commands of the categorical imperative.
This interpretation corresponds with Kant’s classification in the Introduction to the Critique of Judgment where he attaches dietetics to the disciplines which are cases of practical use of natural philosophy according to technically practical principles [7, Bd. 5. 173], [11, 60].
Both concepts have the same supreme principle, namely, the Stoic sustine et abstine. Thus, they are not without connection to each other. But the problem of their unity depends on the general problem of the relation between natural and practical philosophy, respectively, between nature and freedom in Kant.
Dietetics as a free art to avert (physical) illness can be advised by a doctor who does not cure in practice alone but according to his knowledge on nature derived from science. In this regard, the physician is an artist [7, Bd. 7. 26], [9, 254]. The philosopher is authorized by nature, too, to participate in medical dietetics, on the condition that he observes himself and that he does not rely on the experiences of someone else. In this way Kant uses in the Conflict of the Faculties examples from his own biography and talks about himself through introspection [7, Bd. 7. 98], [9, 314]. But, since this kind of regimen follows from technically practical reason, the rules for self-regard are not commanding but only counselling (cf. [7, Bd. 6. 387], [8, 518]).
IV. Ethics as a universal medicine
In the Conflict of the Faculties Kant portrays Hufeland as a philosophical physician. A pure physician executes in a technical way the means given by experience but advised by reason. In this respect he cures merely with skill. But as a member of medical legislation (e. g., of a medical society, or of a medical faculty) he prescribes – combined with the means of cure – what is a duty in itself. Due to this achievement, Kant calls morally practical philosophy a universal medicine (panacea). But this medicine is limited in two ways: first, it does not consist of ethics as a whole but it is reduced to duties to oneself as an animal and moral being. Moreover, these duties can only be negative duties as a means to prevent disease. This is the task of dietetics. Second, universal medicine is not really panacea because it does not cure every illness and not everybody. Its success depends on the mind’s power of the moral agent and on the strength of his resolution, i. e., on his own free will.
Dietetics presupposes an ability that must be given by philosophy alone, namely, by morally practical philosophy. In this regard the supreme task of dietetics – that is, to confirm the power of the human mind, in order to master its morbid feelings – relates to philosophy. Hence, the task of dietetics as a part of morals is not essentially the affair of a doctor.
Finally, we can say, with regard to Kant’s conception of dietetics, that moral health does not imply physical health, although, moral disease includes physical illness because pains that have a moral cause (when the purposes of maxims are vices) are felt as physical effects.
V. Moral aspects of practical problems in medical research
No doubt, Kant’s practical philosophy involves some elements that influenced the discussion on problems of medical practice and research. This circumstance concerns the theory of morals as well as the doctrine of right. For example, in the latter he discusses the question if it is just to reprieve a criminal who is under pain of death, provided that he will offer his life to a physician for medical experiments. Kant denies the view that the science of medicine has a right to dispose of human life in this way because the penal law is a categorical imperative. Therefore, the punishment cannot be justified as a means to another purpose than to the civil right itself [7, Bd. 6. 331], [8, 472 f.].
In his Doctrine of Virtue Kant considers a moral problem entailed by vaccination:
„Anyone who decides to be vaccinated against smallpox puts his life in danger, even though he does it in order to preserve his life; and, insofar as he himself brings on the disease that endangers his life, he is in a far more doubtful situation, as far as the law of duty is concerned, than is the sailor, who at least does not arouse the storm to which he entrusts himself. Is smallpox inoculation, then, permitted?“ [7, Bd. 6. 424], [8, 548].
The historical background of the moral conflict Kant describes here is that vaccination at the end of the 18th century was not developed to perfection. Therefore, a patient risked his life in order to give himself protection against the pocks. Although, the first successful experiment in Königsberg had happened in the year 1757, many people died because of the practice of inoculation. Thus, the problem for a person consisted in the following conflict: his duty to keep himself alive as an animal being on the one hand demands him to be inoculated against the pocks in order to preserve himself from death; on the other hand the same duty demands him not to do so because the inoculation implies that he allows to receive willingly an illness by vaccination that could lead to his death; and this consequence would be similar to suicide (cf. [7, 15.2, 975]). If it was a case of suicide, then inoculation would be a vice conflicting with the duty to himself as an animal being. So, the question was: is it unavoidable to violate the duty to oneself if the animal life is threatened by the pocks? Or, will a person come to a distinctive decision that is consistent with moral law?
Kant was confronted repeatedly with this question. In the year 1799 he received a letter from the Earl Fabian Emil of Dohna who asked the philosopher to explain what „the law is speaking for with regard to one’s own decision on inoculation“. Pointing on the Doctrine of Virtue Kant’s correspondent has scruples about the omission of vaccination. He argues that this would involve a high probability of infection.
There was still another inquiry about this moral problem addressed to Kant one year later. The medical professor Johann Christian Wilhelm Junker asked in the name of the medical society in Halle for Kant’s expert opinion on the question, „if you think the inoculation of the pocks to be moral or immoral, and why“. As far as we know by Kant’s later notes, he had the intention to answer both inquiries by publishing an article (cf. [7, 15.2, 971]) but, in the end, he did not realize this plan.
There is no explicit answer to the question on inoculation in Kant’s Doctrine of Virtue; but we may conclude that Kant favoured the first alternative, that is, that inoculation is moral. His reasoning to answer in this way may be a sort of calculation: it’s still more probable to save one’s life by allowing vaccination than by refraining from it. It seems that for Kant the inquiry on inoculation does not violate moral law, although, the problem may be very difficult (cf. [7, 15.2, 972 f.]). But Kant does not give a definite answer from the view of morality. Nevertheless, it follows from his conception of duties to oneself only that everybody has to choose maxims suitable to avert danger from his life. Whether he decides to be inoculated or not, is a matter of his own reflection and resolution. Obviously Kant was not satisfied with this moral approach to solve a medical problem; for, he suggested that all citizens should be bound by law in vaccination. The government should command inoculation without exception because, then, it would be necessary for everyone and, hence, permitted [7, 15.2, 971 f.].
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 Quotations are taken from The Cambridge Edition of the Works of Immanuel Kant (CE). Writings not incorporated in the CE are based on my own translation. Page numbers in the first position are referring to the Academie edition (source number, volume, page) and, sequently, to the CE.
 Cf. Epictetus, Encheiridion, c. 47 [4, 330-331].
 The transmission of the Greek `ανέχου και `απέχου used conceptually by Epictetus in his Encheiridion (spec. c. 33, 10) [4, 318 f.] into the Latin formula sustine et abstine took place in the year of Kant’s birthday [1, 80].
 Cf. Christoph Wilhelm Hufeland (1762-1836): Die Kunst das menschliche Leben zu verlängern. Jena 1797 (cf ).
 This may be shown by Kant’s use of the concept of the living force in the course of his competition with the anatomical conception of the brain water’s function in Soemmerring‘s Ueber das Organ der Seele (Königsberg 1796) (cf. [5, 453-480]).
 In his letter to Kiesewetter (March 25, 1790) Kant gives his „dearest friend“ appropriately dietetical advises [10, 339 f.].
 I suppose that there is a misleading translation in the text of the Cambridge Edition [9, 316]. My understanding of the German version causes me to propose a reading in the following way: „Hence Stoicism (sustine et abstine) belongs, as the principle of the regimen, not only to pracitcal philosophy as the doctrine of virtue but also [to philosophy] as the science of medicine.“ (cf. [7, Bd. 7. 100]).
 This could also be the reason why Kant condemned the regimen of Moses Mendelssohn in his first official academic speech as Rector of the University of Königsberg (October 10, 1786: De Medicina Corporis quae Philosophorum est) [7, 15.2, 939-953], because he argued that Mendelssohn’s wrong way of life, that is, “an overly severe discipline of the body” had destroyed his organism and led to his death [6, 229 f.], [2, 359 f.]; [7, 15.2, 941-942].
 „What, therefore, should one think of the proposal to preserve the life of a criminal sentenced to death if he agrees to let dangerous experiments be made on him and is lucky enough to survive them, so that in this way physicians learn something new of benefit to the commonwealth? A court would reject with contempt such a proposal from a medical college, for justice ceases to be justice if it can be bought for any price whatsoever.“ [7, Bd. 6 332], [8, 473].
 The date of the letter is 28th August , [7, 12, 283 f].
 Letter from Juncker, June 27, 1800 [1, 12, 314].
 Cf. the letter from J. B. Erhard (16.4.1800) who promised Kant a theory of medical legislation.
This article was firstly published in collected articles «Kant zwischen West und Ost» (2005):
Euler, Werner. The art to keep healthy and to prolong human life. Is Kant’s regimen a doctrine of duties to oneself?// Kant zwischen West und Ost. Zum Gedenken an Kants 200. Todestag und 280. Geburtstag. Hrsg. Von Prof. Dr. Wladimir Bryuschinkin. Bd.2. Kaliningrad, 2005. S. 228 – 237.