Kantian ethics
Kantian ethics refers to a deontological ethical theory developed by German philosopher Immanuel Kant that is based on the notion that "I ought never to act except in such a way that I could also will that my maxim should become a universal law." It is also associated with the idea that "it is impossible to think of anything at all in the world, or indeed even beyond it, that could be considered good without limitation except a good will." The theory was developed in the context of Enlightenment rationalism. It states that an action can only be moral if it is motivated by a sense of duty, its maxim may be rationally willed a universal, objective law.
Central to Kant's theory of the moral law is the categorical imperative. Kant formulated the categorical imperative in various ways. His principle of universalizability requires that, for an action to be permissible, it must be possible to apply it to all people without a contradiction occurring. Kant's formulation of humanity, the second formulation of the categorical imperative, states that as an end in itself, humans are required never to treat others merely as a means to an end, but always as ends in themselves. The formulation of autonomy concludes that rational agents are bound to the moral law by their own will, while Kant's concept of the Kingdom of Ends requires that people act as if the principles of their actions establish a law for a hypothetical kingdom.
The tremendous influence of Kant's moral thought is evident both in the breadth of appropriations and criticisms it has inspired and in the many real world contexts in which it has found application.
Outline
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, 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 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, 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, 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 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. 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, 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.