Although all of Kant's works develop his ethical theory, it is most clearly defined in the
Groundwork of the Metaphysics of Morals, the
Critique of Practical Reason, and the
Metaphysics of Morals. While the
Groundwork of the Metaphysics of Morals is important for understanding Kant's ethics, one will get an
incomplete understanding of his moral thought if one only reads the
Groundwork of the Metaphysics of Morals and the
Critique of Practical Reason, or is not at least aware that his other ethical writings discuss other important details about Kant's moral philosophy as a whole since "one is all the more misled if he is not aware that they form only part of the picture." As part of the
Enlightenment tradition, Kant based his ethical theory on the belief that
reason should be used to determine how people ought to act. He did not attempt to prescribe specific action, but instructed that reason should be used to determine how to behave.
Good will and duty In his combined works, Kant construed as a basis for the ethical law by the concept of
duty. Kant began his ethical theory by arguing that the only virtue that can be an unqualified good is a good will. No other virtue, or thing in the broadest sense of the term, has this status because every other virtue, every other thing, can be used to achieve immoral ends. For example, the virtue of
loyalty is not good if one is loyal to an evil person. The
good will is singularly unique in that it is always good and maintains its moral value regardless of whether or not it achieves its moral intentions. Kant regarded the
good will as a single moral principle that freely chooses to use the other virtues for genuinely moral ends. For Kant, a
good will has a broader conception than a will that acts from duty. A will that acts from duty alone is distinguishable as a will that overcomes hindrances in order to keep the moral law. A dutiful will is thus a special case of a
good will that becomes visible in adverse conditions. Kant argues that only such acts performed with regard to duty have moral worth. This is not to say that acts performed merely in accordance with duty are worthless (these still merit approval and encouragement), but that distinctively
moral esteem is given to acts that are performed out of duty, or from duty, alone. Kant's conception of duty does not entail that people perform their duties grudgingly. Although duty often constrains people and prompts them to act against their inclinations, it still comes from an agent's
volition: they desire to keep the moral law from respect of the moral law. Thus, when an agent performs an action from duty it is because their moral incentives are chosen over and above any opposing inclinations. Kant wished to move beyond the conception of morality as externally imposed duties, and present an ethics of
autonomy, when rational agents freely recognize the claims reason makes upon them.
Perfect and imperfect duties Applying the
categorical imperative, duties arise because failure to fulfill them would either result in a
contradiction in conception or in a contradiction in the will. The former are classified as
perfect duties, the latter as
imperfect. A
perfect duty always holds true. Kant eventually argues that there is in fact only one perfect duty—the categorical imperative. An
imperfect duty allows flexibility—beneficence is an imperfect duty because we are not obliged to be completely beneficent at all times, but may choose the times and places in which we are. Kant believed that perfect duties are more important than imperfect duties: if a conflict between duties arises, the perfect duty must be followed.
Categorical imperative The foundation of Kant's ethics is the categorical imperative, for which he provides four formulations. Kant made a distinction between categorical and
hypothetical imperatives. A
hypothetical imperative is one that people must obey if they want to satisfy our desires: 'go to the doctor' is a hypothetical imperative because they are only obliged to obey it if they want to get well. A
categorical imperative binds them regardless of our desires: everyone has a duty to not lie, regardless of circumstances and even if it is in their interest to do so. These imperatives are morally binding because they are based on reason, rather than contingent facts about an agent. Unlike hypothetical imperatives, which bind them insofar as people are part of a group or society that they owe duties to, they cannot opt out of the categorical imperative because we cannot opt out of being
rational agents. The categorical imperative makes people's duty to the moral law a requirement of reason which holds for them as rational agents; therefore, rational moral principles apply to all rational agents at all times.
Universalizability Kant's first formulation of the categorical imperative is that of
universalizability: Kant defines
maxim as a "subjective principle of volition", which is distinguished from an "objective principle or 'practical law. While "the latter is valid for every rational being and is a 'principle according to which they ought to act[,]' a maxim 'contains the practical rule which reason determines in accordance with the conditions of the subject (often their ignorance or inclinations) and is thus the principle according to which the subject does act. A maxim may be a practical law, yet regardless of whether or not that is so, it is always the principle that the person themself acts from. Maxims lapse into subjectivity, and thus become unable to qualify as practical laws, if they produce a contradiction in conception or a contradiction in the will when universalized. A contradiction in conception happens when, if a maxim were to be universalized, it ceases to make coherent sense because the "maxim would necessarily destroy itself as soon as it was made a universal law." For example, if maxims equivalent to 'I will break a promise when doing so secures my advantage' were universalized, no one would trust any promises, so the idea of a promise would become meaningless; the maxim would be
self-contradictory because, when universalized, promises cease to be meaningful. The maxim is not moral because it is logically impossible to universalize—we could not conceive of a world where this maxim was universalized. A maxim can also be immoral if it creates a contradiction in the will when universalized. This does not mean it is logically impossible to universalize, but that doing so leads to a state of affairs that no
rational being would desire. Kant believed that morality is the
objective law of
reason: just as objective
physical laws necessitate physical actions (e.g., apples fall down because of
gravity), objective rational laws necessitate
rational actions. He thus believed that a perfectly rational being must also be perfectly moral, because a perfectly rational being
subjectively finds it necessary to do what is rationally necessary. Because humans are not perfectly rational (they partly act by
instinct), Kant believed that humans must conform their subjective will with objective rational laws, which he called
conformity obligation. Kant argued that the objective law of reason is
a priori, existing externally from rational being. Just as physical laws exist prior to physical beings, rational laws (morality) exist prior to rational beings. Therefore, according to Kant, rational morality is universal and cannot change depending on circumstance. Some have postulated a similarity between the first formulation of the categorical imperative and the
Golden Rule. Kant himself criticized the Golden Rule as neither purely formal nor necessarily universally binding. His criticism can be seen in a footnote stating: Let it not be thought that the trite
quod tibi non vis fieri etc. [what you do not want others to do to you, etc.] can serve as norm of principle here. For it is, though with various limitations, only derived from the latter. It can be no universal law because it contains the ground neither of duties to oneself nor of duties of love to others (for many a man would gladly agree that others should not benefit him if only he might be excused from showing them beneficence), and finally it does not contain the ground of duties owed to others; for a criminal would argue on this ground against the judge punishing him, and so forth
Humanity as an end in itself Kant's second formulation of the categorical imperative is to treat humanity as an
end in itself: Kant argued that rational beings can never be treated merely as
means to ends; they must always also be treated as
ends in themselves, requiring that their own reasoned motives must be equally respected. This derives from Kant's claim that the sense of
duty, the rational
respect for law, motivates
morality: it demands that we respect the rationality of all beings. A rational being cannot rationally consent to be used merely as a means to an end, so they must always be treated as an end. Kant justified this by arguing that moral obligation is a rational necessity: that which is rationally willed is morally right. Because all rational agents rationally will themselves to be an end and never merely a means, it is morally obligatory that they are treated as such. This does not mean that we can never treat a human as a means to an end, but that when we do, we also treat them as an end in themselves.
Formula of autonomy Kant's
formula of autonomy expresses the idea that an agent is obliged to follow the categorical imperative because of their rational will, rather than any outside influence. Kant believed that any moral law motivated by the desire to fulfill some other interest would deny the categorical imperative, leading him to argue that the moral law must only arise from a rational will. This principle requires people to recognize the right of others to act autonomously and means that, as moral laws must be universalizable, what is required of one person is required of all.
Kingdom of Ends Another formulation of Kant's categorical imperative is the
Kingdom of Ends: This formulation requires that actions be considered as if their
maxim is to provide a law for a hypothetical Kingdom of Ends. Accordingly, people have an obligation to act upon principles that a community of
rational agents would accept as laws. In such a community, each individual would only accept maxims that can govern every member of the community without treating any member merely as a means to an end. Although the Kingdom of Ends is an ideal—the actions of other people and events of nature ensure that actions with good intentions sometimes result in harm—we are still required to act categorically, as legislators of this ideal kingdom.
The Metaphysics of Morals As Kant explains in the
Groundwork of the Metaphysics of Morals (and as its title directly indicates), that short 1785 text is "nothing more than the search for and establishment of the
supreme principle of morality." Kant further states, just because moral laws are to hold for every rational being as such, to derive them from the universal concept of a rational being as such, and in this way to set forth completely the whole of morals, [a metaphysics of morals] needs anthropology for its
application to human beings. His promised
Metaphysics of Morals, however, was much delayed and did not appear until its two parts, The Doctrine of Right and The Doctrine of Virtue, were published separately in 1797 and 1798. In the twelve years between the
Groundwork and The Doctrine of Right, Kant decided that the metaphysics of morals and its application should, after all, be integrated (though still as distinct from practical anthropology). The distinction between its groundwork (or foundation) and the metaphysics of morals itself, however, continues to apply. Moreover, the account provided in the latter
Metaphysics of Morals provides "a very different account of ordinary moral reasoning" than the one suggested by the
Groundwork. The Doctrine of Right deals with
juridical duties, which are "concerned only with protecting the external freedom of individuals" and indifferent to incentives. (Although we do have a moral duty "to limit ourselves to actions that are right, that duty is not part of [right] itself.") Its basic political idea is that "each person’s entitlement to be his or her own master is only consistent with the entitlements of others if public legal institutions are in place." The Doctrine of Virtue is concerned with
duties of virtue or "ends that are at the same time duties." It is here, in the domain of ethics, that
The Metaphysics of Morals's greatest innovation is to be found. According to Kant's account, "ordinary moral reasoning is fundamentally teleological—it is reasoning about what ends we are constrained by morality to pursue, and the priorities among these ends we are required to observe." More specifically, There are two sorts of ends that it is our duty to have: our own perfection and the happiness of others (
MS 6:385). "Perfection" includes both our natural perfection (the development of our talents, skills, and capacities of understanding) and moral perfection (our virtuous disposition) (
MS 6:387). A person’s "happiness" is the greatest rational whole of the ends the person set for the sake of her own satisfaction (
MS 6:387–8). Kant's elaboration of this teleological doctrine offers up a very different moral theory than the one typically attributed to him on the basis of his foundational works alone. ==Influences on Kantian ethics==