The One Problem with Kantian Ethics

By Neel Burton | June 13, 2026

Is Kant’s Categorical Imperative too rigid?

When obeying those moral laws that we could consistently and rationally will as universal laws, we are following the so-called Categorical Imperative, which might be re-stated as, “Always act such that the maxim of your action can at the same time be upheld as a universal law.”

This is similar to the much older Golden Rule of the Bible and Indian Mahabharata, according to which we should treat others as we would wish to be treated. But whereas the Golden Rule is based on personal desire, which is subjective (I might, for example, be a masochist, or be willing to tolerate some mistreatment), the Categorical Imperative is based on reason, which is objective.

Hypothetical vs Categorical Imperatives

Hypothetical imperatives are practical rules for achieving a desired outcome, for example, “If you want to lose weight, you should watch what you eat.” If you do not desire a particular outcome, you do not need to follow the rules. In this much, hypothetical imperatives are conditional and contingent. In contrast, Categorical Imperatives are universal moral commands that bind everyone regardless of their aims, for example, “Do not lie,” “Do not steal,” “Do not commit suicide.”

Hypothetical imperatives answer to the lower faculty of desire, which aims at pleasure. Categorical Imperatives answer to the higher faculty of will, which functions rationally and autonomously by following the laws which it legislates for itself, regardless of consequences or personal feelings.

For Kant, true moral actions must be motivated by duty, not some desired outcome. Thus, Kantian ethics are sometimes described as deontological, or duty-based [Greek, deon, “duty”], and contrasted with consequentialism (for example, utilitarianism), which is outcome-based. For Kant, moral systems based on outcomes or desires operate on hypothetical imperatives, not true moral law.

Some Examples of the Categorical Imperative

Kant furnishes some examples to flesh out the bones of the Categorical Imperative. Imagine a person in financial need who borrows money and promises to pay it back, knowing full well that they never will. If this action were universalised, promises of repayment would no longer be believed and the practice of lending would end.

When we help someone, our action must be motivated by duty if it is to have moral worth. If I help someone from inclination, for example, from sympathy or because it makes me feel good, I am still doing a praiseworthy thing, but my action, being circumstantial rather than principled and reliable, lacks moral worth. Imagine a grocer who always gives the correct change, but only to avoid being caught and losing his reputation. His behaviour, though not blameworthy, is lacking in moral worth. If he knew that he could not possibly get caught, he may start behaving dishonestly. Because his behaviour is prudential and circumstantial rather than born out of duty, it is not categorical.

For Kant, a paradigm of moral worth is the person who hates life and longs to commit suicide, but stays alive purely out of duty. Because this person has no self-serving inclinations, he is acting purely from duty, rather than mere “conformity to duty.” Similarly, and counterintuitively, a hard-hearted person who has no other motivation than duty has a moral worth “beyond all comparison the highest.”

The Humanity Formulation of the Categorical Imperative

The universalizability formulation is the first formulation the Categorical Imperative. The second formulation is the humanity formulation, or end-in-itself formulation: “Act always treating humanity, in yourself and others, as an end and never merely as a means.”

Like Aristotle, Kant argued that everything that has instrumental value derives this value from the end that it serves. Thus, for anything to have value, there must be some end that has intrinsic worth, that is, some end that is an end-in-itself. For Aristotle, this “supreme good” was happiness, or eudaimonia. For Kant, it was a rational being who could freely determine his or her own ends. In all of nature, man alone is an end-in-itself, and must therefore be treated as such.

We can only use others (like waiters and cab drivers) as means if we respect their own ends and agency, treating them as rational beings with purposes of their own rather than mere tools for achieving ours. You can employ a servant if you pay and treat them fairly, and the servant wills it because working for you furthers their own ends. Although Kant never applied the humanity formulation to specifically and explicitly condemn the transatlantic slave trade, his moral philosophy provided the framework for later abolitionists.

Benjamin Constant’s Challenge to Kant

In the aftermath of the Reign of Terror (1793-1794), a period during the French Revolution marked by mass executions of perceived enemies, the Swiss writer Benjamin Constant conceived of a thought experiment to undermine Kantian ethics.

Imagine an axe-wielding murderer at your door, asking where your friend, who has taken refuge in your house, is hiding. Although, according to Kant, lying is always wrong, it would be absurd to speak the truth and reveal your friend’s location to the murderer. In this scenario, surely, the duty to protect your friend overrides any duty to tell the truth. What’s more, by intending to commit a grave injustice, the murderer has forfeited any right to the truth.

Kant responded to Constant in his 1797 essay, On a Supposed Right to Tell Lies from Benevolent Motives, and dug in his heels. Even in those circumstances, it would be wrong to lie. The morality of an action is determined by its principles, not its consequences. One could not know whether lying would do more good than harm to one’s friend in hiding. Whereas one would be responsible for the consequences of telling a lie, the consequences of telling the truth would be on the murderer. Moreover, to lie to the murderer would be to treat him as a mere means to an end, denying him the status of a rational being capable of free, reasoned action.

The One Problem with Kantian Ethics—and a Solution

Kant’s rigid application of the Categorical Imperative led him to condemn many actions and behaviours that are no longer generally condemned, such as masturbation and suicide out of world-weariness. He referred to masturbation as an “unnatural vice” on the basis that the natural purpose of sex is procreation.

The Categorical Imperative is, no doubt, a good rule of thumb, but must admit of exceptions. Exceptions, too, are a matter of judgement and reason—more so even than the rules themselves.

Kant’s Categorical Imperative Explained

By Neel Burton | January 2, 2026

Would You Lie to Save an Innocent Life?

Kant insisted that we should never lie—not even to a killer at the door.

Article substantially revised on 24 July 2026.

Imagine a killer at your door asking whether the person hiding in your house is there. Would you tell a lie? Most of us would. Immanuel Kant thought we shouldn’t. For Kant, lying is always wrong, no matter the circumstances.

Despite his love of hosting, conversation, and fine dining, Kant’s house was unadorned and austere. He had only one picture, which hung above his bureau. This picture was of Jean-Jacques Rousseau, who was only 12 years older than him. According to lore, the only time Kant failed to take his daily walk was when he received his copy of Rousseau’s Émile.

How did Rousseau’s outlook work its way into Kant’s moral philosophy? If, for Rousseau, it is by following the ‘general will’ that we can be said to be free, for Kant, it is by obeying those moral laws that we would will as universal laws. Moral laws that we would will as universal laws are given not by our individual will but by our rational will, which we have in common with all other rational beings.

We often experience this dichotomy in our minds: this is what I selfishly or frivolously want to do, and this is what I truly ought to do—because I want to live in a better society that abides by this rule, and would resent it if other people behaved in such a biased, thoughtless way.

To conform to the universal law is not to be a slave; on the contrary, it is to follow reason and free ourselves from our irrational and disordered appetites. For Kant, this capacity to overrule our individual will lies at the heart of our special dignity as human beings.

For Kant, morality rests not on God, tradition, authority, or emotion, but on reason itself. Through the Categorical Imperative, he sought to place morality on an objective, rational foundation. Since all rational beings share the same rational nature, they should arrive at the same moral principles if they reason correctly.

The Categorical Imperative vs. the Golden Rule

When obeying those moral laws that we could consistently and rationally will as universal laws, we are following the so-called Categorical Imperative, which might be re-stated as, ‘Always act such that the maxim of your action can at the same time be upheld as a universal law.’

This is similar to the much older Golden Rule of the Bible, according to which we should treat others as we would want to be treated. But whereas the Golden Rule is based on personal desire, which is subjective (I might, for example, be a masochist, or be willing to tolerate a degree of mistreatment), the Categorical Imperative is based on reason, which is objective.

Hypothetical Imperatives and Consequentialism

Hypothetical imperatives are practical rules for achieving a desired outcome, for example, ‘If you want to lose weight, you should watch what you eat.’ If you do not desire a particular outcome, you do not need to follow the rules. In this much, hypothetical imperatives are conditional and contingent. Categorical Imperatives, in contrast, are universal moral commands that bind everyone regardless of their aims, for example, ‘Do not lie’ or ‘Do not steal.’

For Kant, true moral actions must be motivated by duty, not some desired outcome. Thus, Kantian ethics are sometimes described as deontological, or duty-based, and contrasted with consequentialism (for example, utilitarianism), which is outcome-based. For Kant, moral systems based on outcomes or desires, such as utilitarianism, operate on hypothetical imperatives, not true moral law.

Perfect vs. Imperfect Duties

Kant provides some examples to add flesh to the bones of the Categorical Imperative. Imagine a person in financial need who borrows money and promises to pay it back, in the knowledge that they never will. If this action were universalised, promises of repayment would no longer be believed, and the entire practice of lending would collapse. Kant also points out that abusing the lender in this way reduces a dignified being with ends of his own to a mere means to an end (‘Act always treating humanity, in yourself and others, as an end and never merely as a means’ is the second formulation of the Categorícal Imperative).

Second, imagine a person who does not intervene to help a person in distress. Were this maxim to be universalised, no one would ever help anyone, making the world a worse place.

In the first case, not repaying a loan, the maxim cannot be universalised because it would involve a contradiction. In the second case, not helping a person in distress, there is no such contradiction. Nonetheless, it would not be rational to will a world in which no one ever helped anyone. Whereas repaying a loan is a ‘perfect duty’, helping someone in need is an ‘imperfect duty’ in that we have some latitude in how we go about fulfilling it. Though we ought to be benevolent, we do not need to go about helping everyone all the time.

Failing in an imperfect duty, such as helping others or cultivating our talents, does not attract the same strict blame as violating a perfect duty, so long as we do not adopt a maxim contrary to the imperfect duty.

Kant’s Example of the Prudent Grocer

When we do help someone, our action must be motivated by duty if it is to have moral worth. If I help someone from inclination, for example, from sympathy or because it makes me feel good, I am still doing a praiseworthy thing, but my action, being circumstantial rather than principled and reliable, lacks moral worth.

Imagine a grocer who always gives the correct change, but only to avoid being caught and losing his reputation. His behaviour, though not blameworthy, is lacking in moral worth. If he knew that he could not get caught, he might behave differently and dishonestly. Because his behaviour is prudential and circumstantial, rather than born out of duty, it is not categorical.

For Kant, a paradigm of moral worth is the person who hates life and longs to commit suicide, but stays alive purely out of duty. Because this person has no self-serving inclinations, he is acting purely from duty, rather than mere ‘conformity to duty’. Similarly, a hard-hearted person who has no other motivation than duty has a moral worth ‘beyond all comparison the highest’.

How to Identify the Categorical Imperative

During his trial in Jerusalem in the 1960s, the Nazi Adolf Eichmann, a major organiser of the Holocaust, claimed to have been abiding by Kant’s Categorical Imperative—having interpreted ‘doing your duty’ as blind obedience to superior authorities.

To identify the Categorical Imperative, we need to look inward to our rational self and engage in our own moral reasoning—asking whether the maxim guiding our action could be universalised—rather than delegate responsibility to some external authority such as a dictator (say, Hitler) or even a religious doctrine (say, the Ten Commandments).

So long as they reason correctly, every rational being, human or otherwise, should be able to arrive at the same Categorical Imperative. As pure rational wills, shorn of our attributes, temperaments, and desires, we are all the same. Whenever we act with a moral dimension, we implicitly universalise that action for all other wills.

In her analysis of the Eichmann trial, the philosopher Hannah Arendt introduced the concept of the ‘banality of evil’, highlighting that evil can be perpetrated not only by fanatics and psychopaths, but, more ordinarily, by ‘normal’ people who fail to engage in critical self-reflection.

Constant’s Challenge: The Killer at the Door

Imagine a murderer at your door, asking where your friend, who has taken refuge in your house, is hiding. Although, according to Kant, lying is always wrong, it would be absurd to speak the truth and reveal your friend’s location to the murderer. In this scenario, the duty to protect your friend overrides any duty to tell the truth. Moreover, by intending to commit a grave injustice, the murderer has forfeited any right to the truth.

Whether or not we agree with Kant’s response, the Categorical Imperative continues to raise one of the deepest questions in ethics. Should moral principles admit exceptions, or do they cease to be moral principles once they do? More than two centuries later, the killer is still at the door, reminding us that the true test of morality comes not when doing the right thing is easy, but when it seems to cost us everything.

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To explore Kant’s ideas in their historical context—and discover how they influenced Hegel, Schopenhauer, and Nietzsche—see my book The German Greeks.

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Aristotle’s Golden Mean

By Neel Burton | April 18, 2023

Is There a Right Amount of Anger?

Golden musical notes, a beautiful harmony — Virtue, like music, depends not on the right amount, but on the right measure.

By Dr Neel Burton — Psychiatrist, philosopher, and wine writer; Fellow of Green Templeton College, University of Oxford; author of over twenty books.

This article is a faithful exposition of Aristotle’s account of virtue in Book II of the Nicomachean Ethics.

Aristotle’s account of moral virtue rests on a simple but demanding idea: that goodness is not something we possess by nature, but something we acquire through practice.

In Book 2 of the Nicomachean Ethics (c. 330 BCE), Aristotle argues that moral virtues are formed through repetition. Unlike sight and hearing, which are given to us at birth, virtue is not in our nature. But neither is it contrary to our nature, which is adapted to receive it. Just as a sculptor becomes a sculptor by sculpting, so the virtuous become virtuous by exercising virtue.

One cannot define virtue with any precision because the goodness of a feeling or action is highly person- and context-dependent. All that can be said is that virtue, like strength, is undermined by a lack or excess of training. For instance, he who flees from everything becomes a coward, while he who runs headlong into every danger becomes rash. Courage, in contrast, is indicated and produced by the mean.

Moral excellence is intimately related to pleasure and pain. For it is in the pursuit of pleasure and avoidance of pain that bad deeds are committed, and good deeds omitted. Hence, it is by pleasure and pain that bad people are bad.

There are three objects of choice, the noble, the advantageous, and the pleasant, and three objects of avoidance which are their contraries, the base, the injurious, and the painful. The good tend to go right about these, whereas the bad tend to go wrong. This is especially true of pleasure, which is common to the animals, and also contained in the advantageous and the noble. The good feel pleasure from the most beautiful, noble [kalos] actions, but the bad or not-good are often confused about what is most pleasant. It is harder to fight with pleasure than with anger, but virtue, like art, is concerned with what is harder, and the good is better when it is harder.

A person may perform an apparently virtuous action by chance or under duress. An action is only virtuous if it is recognised as being virtuous and performed for that sake by a person with a set, unvarying character. In sum, an action is only virtuous if it is such as a virtuous person would perform.

The Golden Mean

Three things are found in the soul: passions, faculties, and dispositions [hexeis]. As the virtues are neither feelings nor faculties, they must be dispositions: dispositions to aim at the intermediate, or mean, between deficiency and excess.

The principal virtues, together with their corresponding vices, are listed in the table below.

Aristotle's table of the virtues, with the golden mean, the excess, and the deficiency — Copyright Neel Burton

In any sphere, arriving at the mean is a form of success and worthy of praise. While it is possible to fail in many ways, it is possible to succeed in one way only, which is why the one is easy and the other is difficult. By the same token, men may be bad in many ways, but good in one way only.

So far so good, except that not every passion or action admits of a mean: for instance, not envy or murder. It is never a question of murdering the right person, at the right time, in the right way, for murder is neither a deficiency nor an excess, but always and intrinsically vicious.

The principal virtues along with their corresponding vices are listed in the table below.

In some cases, one vice can be closer to the virtue than the contrary vice, for instance, rashness is closer to courage than cowardice, and prodigality is closer to liberality than meanness. This is partly because the contrary vice, whether cowardice or meanness, is more common. Hence, people oppose not rashness but cowardice to courage, and not prodigality but meanness to liberality.

It is no easy task to be good. To increase the likelihood of hitting the mark, we should (1) avoid the vice that is furthest from the virtue or mean; (2) consider our vices and drag ourselves towards their contrary extremes; and (3) be wary of pleasure and pain.

For in everything it is no easy task to find the middle… anyone can get angry—that is easy—or give or spend money; but to do this to the right person, to the right extent, at the right time, with the right motive, and in the right way, that is not for everyone, nor is it easy; wherefore goodness is both rare and laudable and noble.

The Golden Mean (Virtue Ethics) vs the Categorical Imperative vs Utilitarianism

Aristotle’s ethics differs fundamentally from the two great ethical systems that came after him. Utilitarianism asks, ‘Which action will produce the most happiness?’ Kantian ethics asks, ‘Which action accords with strict moral duty?’ Aristotle begins somewhere else entirely: ‘What kind of person should I be?’ For him, ethics is not primarily about calculating consequences or obeying rules, but about cultivating character. The virtuous person develops, through practice and experience, the subtle judgement to feel and act in the right way, to the right degree, at the right time, and for the right reasons. Instead of giving us a crude formula for making moral decisions, Aristotle asks us to become the sort of person who can make them intuitively.

Sometimes, we may somewhat miss the mark, for instance, get angry too soon or not enough, yet still be praiseworthy. It is only when we deviate more markedly from the mean that we become blameworthy.

We help others by being virtuous, but we also help ourselves, for virtue is a disposition to happiness, and happiness is the exercise of virtue.