Unit 5: Justice

90 How can punishment be justified? On Kant’s Retributivism

Guus Duindam

Guus Duindam is a Ph.D Candidate in Philosophy at the University of Michigan working in normative ethics, the philosophy of law, and Kant. Guus also holds a law degree from Michigan Law and currently works as a judicial law clerk at the U.S. District Court for the Eastern District of Michigan.

The institution of legal punishment imposes serious harms on lawbreakers. What, if anything, justifies this practice? In this Chapter, you will learn about the definition of legal punishment, why we need a philosophical justification for it, and what kinds of justifications have been offered by philosophers so far. You will also read Immanuel Kant’s (1724-1804) retributivist defense of punishment.

What is punishment? Why do we need a theory of punishment?

Most philosophers agree that legal punishment has five components: it is the (1) intentional infliction of (2) a harm (3) by a legitimate authority, (4) on someone the authority believes has broken the law, (5) because the authority believes that they’ve broken the law. So: if the United States government sentences Alfred A. to prison because he robbed the local Walmart, that’s an instance of legal punishment. Indeed, it’s an instance of punishment even if Alfred is in fact innocent, so long as the sentencing authority believes him to be guilty. It is, after all, possible to punish the wrong person. But if the government secretly kidnaps Alfred and locks him up because he has compromising information about an illegal government program, that does not count as punishment, even if Alfred also robbed the local Walmart. After all, in this example Alfred’s imprisonment has nothing to do with his having broken the law.

Although we won’t discuss non-legal punishment in this Chapter, it’s interesting to note that all the same conditions seem to apply to non-legal punishment as well. If a parent takes away her child’s candy because she hit her sister, that seems like punishment—and it meets the conditions: the parent is a legitimate authority, taking away the candy is meant to be unpleasant, and it’s done because the child hit her sister, a breach of a moral rule. If you remove any one of the conditions from the example, it will no longer feel like an example of punishment. Imagine, for instance, the candy being taken away because it’s bad for the child’s health; the sister instead of the parent taking the candy away (as retaliation, perhaps), etc. So the five defining conditions of punishment seem to be fairly universal.

Why do we need a philosophical justification of the practice of legal punishment? In an important paper about this issue, Mitchell Berman explains that:

Justification can always be given. There is always some sense in offering the reasons that support one’s conduct. But while they may always be offered, justifications cannot always be demanded. Customarily, to claim that actual or contemplated conduct, X, is “in need” of justification means that “ordinarily” or “presumptively” one ought not to X, or that there exists apparent or putative reason not to X. That is, our practice of justification is a dialectical one in which the initial argumentative burden rests on those who deny or question justification.[1]

In other words: it’s always possible to justify the things we do, because we could always give our reasons for doing it. For instance, we could provide a justifying theory of toothbrushing by appealing to its health and hygiene benefits. But in some cases, someone can demand a justification for our practice. That is true when our practice is presumptively problematic, which means there’s something about the practice that would normally make it morally wrong. Virtually every philosopher agrees that the practice of legal punishment is presumptively problematic in this way. Punishment needs to be justified because normally it would be wrong to intentionally harm other people.

To see why, let’s return to Alfred. Imagine that Bertold B., Alfred’s neighbor, finds out that Alfred robbed the local Walmart. Instead of calling the police, Bertold simply locks Alfred up in his own basement. Bertold’s behavior seems (is) insane. It’s totally unacceptable to lock someone up in your basement—even if they’ve committed one (or many!) crimes. But from Alfred’s perspective, being locked in Bertold’s basement is not so much worse than being locked up in prison. (If Bertold has a nice basement, it might even be better!) So the obvious wrongness of Bertold’s behavior shows us something important: the kind of thing that we do to punish lawbreakers would normally be morally wrong. That is why the practice of punishment is in need of a philosophical justification. When we intentionally harm someone, that person is entitled to demand that we explain ourselves.

Backwards, Forwards, or Both?

Many different attempts at a justification for punishment exist, but they can be grouped into three categories: forward-looking theories, backward-looking theories, and hybrid theories. Forward-looking theories try to defend the institution of punishment by appealing to its social benefits. Such theories are forward-looking because they justify punishment by pointing to the good things that will happen after the punishment is imposed. They are also called utilitarian theories of punishment, because they focus on the practical utility (usefulness) of punishment.

The most important social benefit of punishment is usually thought to be deterrence. Deterrence refers to the idea that punishing people who have committed crimes will discourage other people from committing those crimes as well. In this sense, punishments function a bit like threats: don’t commit crimes, or else…! John Stuart Mill (1806 – 1873), one of the founders of utilitarian ethics, once argued in a speech to the U.K. Parliament that deterrence should be considered the primary purpose of punishment. “To deter by suffering from inflicting suffering is not only possible, but the very purpose of penal justice.” A secondary social benefit of punishment is that wrongdoers will be incapacitated from committing crimes while they are being punished. In the case of dangerous criminals, such incapacitation provides additional societal protection.

Backward-looking theories of punishment take a very different approach. They justify punishment not by looking at its practical benefits but by appeal to what the wrongdoer deserves. This kind of theory is also known as retributivism, because it characterizes punishment as deserved retribution for a moral wrong. According to retributivists, those who break the law commit a moral wrong. And those who commit moral wrongs deserve to suffer. Because it is good when people get what they deserve, it is good when wrongdoers suffer. Accordingly, punishment is justified because it imposes deserved harms. Immanuel Kant is usually considered the most important retributivist theorist of punishment.

Finally, hybrid theories combine aspects of the two other kinds of theories of punishment. For instance, one could argue that punishment is permissible (morally acceptable) because it is deserved, and useful because it protects society. Many hybrid theories also discuss the use of punishments for rehabilitation: helping criminals re-enter society in a more productive way. These kind of theories are hybrid theories because they use both the backward- and the forward-looking justifications. Many modern theories of punishment involve such ‘hybrid’ justifications.

Kant’s Retributivism

In the following sections, we will look closely at Immanuel Kant’s famous retributivist defense of punishment. First, will read an excerpt of Kant’s Doctrine of Right, the work which contains almost all of his legal philosophy. Then, we will consider the implications of Kant’s remarks.

Immanuel Kant, “On the right to punish and to grant clemency,” in the Metaphysics of Morals[2]

The right to punish is the right a ruler has against a subject to inflict pain upon him because of his having committed a crime. […]. Punishment by a court—this is distinct from natural punishment, in which vice punishes itself and which the legislator does not take into account—can never be inflicted merely as a means to promote some other good for the criminal himself or for civil society. It must always be inflicted upon him only because he has committed a crime. For a human being can never be treated merely as a means to the purposes of another or be put among the objects of rights to things: his innate personality protects him from this, even though he can be condemned to lose his civil personality. He must previously have been found punishable before any thought can be given to drawing from his punishment something of use for himself or his fellow citizens. The law of punishment is a categorical imperative, and woe to him who crawls through the windings of eudaimonism in order to discover something that releases the criminal from punishment or even reduces its amount by the advantage it promises, in accordance with the Pharisaical saying, “It is better for one man to die than for an entire people to perish.” For if justice goes, there is no longer any value in human being’s living on the earth. What, therefore, should one think of the proposal to preserve a 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.

But what kind and what amount of punishment is it that public justice makes its principle and measure? None other than the principle of equality (in the position of the needle on the scale of justice), to incline no more to one side than to the other. Accordingly, whatever undeserved evil you inflict upon another within the people, that you inflict upon yourself. If you insult him, you insult yourself; if you steal from him; you steal from yourself; if you strike him, you strike yourself; if you kill him, you kill yourself. But only the law of retribution (ius talionis)—it being understood, of course, that this is applied by a court (not by your private judgment)—can specify definitely the quality and the quantity of punishment; all other principles are fluctuating and unsuited for a sentence of pure and strict justice because extraneous considerations are mixed into them. Now it would indeed seem that differences in social rank would not allow the principle of retribution, of like for like, but even when this is not possible in terms of the letter, the principle can always remain valid in terms of its effect if account is taken of the sensibilities of the upper classes. A fine, for example, imposed for a verbal injury has no relation to the offense, for someone wealthy might indeed allow himself to indulge in a verbal insult on some occasion; yet the outrage he has done to someone’s love of honor can still be quite similar to the hurt done to his pride if he is constrained by judgment and right not only to apologize publicly to the one he has insulted but also to kiss his hand, for instance, even though he is of a lower class. Similarly, someone of high standing given to violence could be condemned not only to apologize for striking an innocent citizen socially inferior to himself but also to undergo a solitary confinement involving hardship; in addition to the discomfort he undergoes, the offender’s vanity would be painfully affected, so that through his shame like would be fittingly repaid with like.

[…] If, however, [someone] has committed murder, he must die. Here there is no substitute that will satisfy justice. There is no similarity between life, however wretched it may be, and death, hence no likeness between the crime and the retribution unless death is judicially carried out upon the wrongdoer, although it must still be freed from any mistreatment that could make the humanity in the person suffering it into something abominable. Even if a civil society were to be dissolved by the consent of all its members (e.g., if a people inhabiting an island decided to separate and disperse throughout the world), the last murderer remaining in prison would first have to be executed, so that each has done to him what his deeds deserve and blood guilt does not cling to the people for not having insisted upon this punishment; for otherwise the people can be regarded as collaborators in this public violation of justice.

Interpreting Kant’s Defense of Retributivism

Kant’s text is dense and sometimes difficult to understand. In this section, we’ll examine the arguments he makes more closely. In the passage provided above, he makes three key points. First, he rejects all forward-looking theories of punishment. Second, he argues that the severity of a punishment may never be increased or decreased because of considerations of societal utility. Third, he defends the principle of retribution or the lex talionis: the idea that punishments should inflict a harm that is similar to the kind the wrongdoer inflicted on their victims. We’ll discuss each argument in turn.

Kant begins with the claim that punishment “can never be inflicted as a means to promote some other good for the criminal himself or for civil society.” This is a direct rejection of forward-looking theories of punishment, which, as we’ve seen, hold that promoting the good of society is the only purpose of punishment. According to Kant, we can’t consider the usefulness of a punishment at all until we’ve determined that someone is “punishable.” By this Kant means to say that we do not have a right to punish anyone who does not deserve to be punished. That is because, in Kant’s view, we have an innate right never to be used simply as a tool to make society better. To be used “merely as a means”—only as a tool—is incompatible with the respect we are owed as human beings. As you will learn if you study Kant in more detail, the principle that we may never use human beings as mere means to our own purposes is one of the key principles of his ethics. He appeals to that principle here to argue that we violate someone’s basic human rights if we punish them just to make society a better place. Instead, punishments are never justified unless we first determine that the wrongdoer actually deserves them.

Implicit in Kant’s rejection of forward-looking accounts of punishment is the accusation that such theories would accept or even encourage punishment of those who do not deserve to be punished. This continues to be a problem for some types of utilitarian theories today. Imagine that the population of State X believes that Cecile C. has committed a horrendous crime. The State knows that Cecile is innocent, but they don’t know who actually committed the crime. So, the Sate punishes Cecile. This deters other people in X from committing similar crimes, reduces public unrest about the unsolved crime, and increases the public’s sense of safety. Some utilitarian theories of punishment would condone the punishment of Cecile in this instance, despite the fact that she is innocent. In contrast, Kant’s theory rejects punishment of the innocent in every case, no matter how useful it would be, because punishment of the innocent is always undeserved.

Kant next turns his attention to the severity of punishments. He argues that we also may not consider the utility of a punishment when we determine how severe it should be. That means we may not impose a punishment that is more severe than the wrongdoer deserves, but we also may not impose a punishment that is less severe. We should determine the severity of our punishments by thinking only about what the wrongdoer deserves, without considering the usefulness of the punishment. As Kant puts it, punishments must be proportional to the criminal’s “inner wickedness.”

This part of Kant’s argument is essentially a defense of proportional punishment. Most people share the intuition that punishments shouldn’t be much worse than the crime warrants—even if that would be societally useful. An extreme example can help illustrate this issue. Imagine that we could significantly reduce traffic deaths by imposing the death penalty on anyone who drives more than ten miles over the speed limit. And imagine that drivers are so scared of being sentenced to death that they all start following the speed limit. (This would be an example of deterrence). As a result, the number of people who die from this new death sentence law is much smaller than the number of people who currently die as a result of speeding related traffic accidents. So this criminal law would save a significant number of lives. Nevertheless, it seems unreasonably harsh. Most people would not support a death sentence for traffic violations even if it would ultimately save lives. In that sense, most people share Kant’s intuition that punishments must be proportional to the wrong they are meant to punish.

Kant also makes the argument in the other direction: he also argues that punishments shouldn’t be less severe than deserved. He makes that point with the example about the prisoner who “agrees to let dangerous experiments be made on him” in return for a shorter sentence. Kant would not permit reductions in sentence in return for social benefits. He defends that view primarily by appeal to the principle of equality. Kant views the unequal treatment of those who have committed crimes that are equally morally wrong as unjustifiable. “Justice ceases to be justice,” Kant says, “if it can be bought for any price whatsoever.” On Kant’s view, then, punishments are non-negotiable: everyone should get exactly what they deserve—no more, no less.

In the context of punishment, Kant’s views often seem strict and uncompromising. Interestingly, though, many of us share Kant’s general intuition that it is a violation of the principle of equality if someone is made better off than they deserve. Consider, for instance, your college grades. Suppose that Derrick D., a classmate of yours, wrote a terrible paper, thrown together in the hour before class. You, in contrast, spent weeks writing the perfect essay. It seems unjust if Derrick gets the same grade as you do—even if you get exactly the grade you deserve. In other words: you might object to Derrick being better off than he deserves in relation to the other people in the class. Kant’s view relies on much the same intuition. If A and B commit equally wrong acts, A and B’s punishment should be precisely identical.

This raises a question about how to determine appropriate punishments. Kant tells us that we should proportion punishments to the “inner wickedness” of the criminal, but how can we decide what the proportional punishment should be? That question continues to be a serious problem for retributivists. There doesn’t seem to be an easy and reliable way to figure out exactly how much suffering someone deserves. As you have read, Kant defends the law of retribution or the lex talionis as an answer to this problem. The ancient lex talionis is the “eye for an eye, tooth for a tooth” principle according to which the punishment should mirror the crime. Of course, Kant does not take that principle literally. He does not argue that we should steal from thieves, insult those who have defamed us, or torture our torturers. As is made clear by his discussion of punishment for the “upper classes,” Kant instead argues that we should impose punishments which impose a harm on the wrongdoer that is similar to the harm the wrongdoer imposed on his victim.

Kant’s own examples are helpful to understand what this principle would mean in practice. He considers a rich nobleman who insults someone of lower social rank. That wrongful act should not be punished with a fine, because then “someone wealthy might indeed allow himself to indulge in a verbal insult on some occasion.” In other words: fines are not suitable punishments because those who are rich enough don’t suffer from them. Instead, they might just choose to commit the crime and pay the fine. So, Kant argues, the nobleman should instead be punished for his insult by being forced to apologize publicly and kissing the hand of his victim. These are things the nobleman will find humiliating, and so he will experience a kind of harm (humiliation) that is similar to the harm he inflicted.

There is another reason we can’t take the lex talionis literally and mirror the crime, and that is that the crime may be too terrible to replicate on the criminal. Kant argues that even the death penalty must be carried out “freed from any mistreatment that could make the humanity in the person suffering it into something abominable.” In other words: we are required to respect the humanity of even the worst imaginable wrongdoers. That means that we may not torture, mistreat, or otherwise disrespect criminals as we try to punish them. Instead, even very serious punishments must be inflicted in a way that is consistent with our respect for the human dignity which we all share.

We have now reviewed the three key aspects of Kant’s defense of retributivism: his rejection of all forward-looking justifications of punishment, his defense of proportionality, and his defense of a modified law of retribution. But we have not addressed the elephant in the room: Kant’s claim that even if a society were disbanding entirely, it still has a moral obligation to execute “the last murderer remaining in prison.” That claim has made Kant notorious as an extremely unforgiving retributivist. Indeed, some philosophers have argued that retributivism of this kind is completely barbaric.[3] Of course, that may be true. (And in any case, today we might no longer believe that it is possible to sentence someone to death while at the same time respecting their dignity as a human being). Whatever you think of Kant’s radical example, though, it is important to recognize that even here, Kant is attempting to apply the principle of equality in a consistent way. In part because of the extreme nature of the example, Kant is sometimes misunderstood as defending a theory of punishment that is based on a desire for revenge. That is not correct. In fact, Kant argues that we have a duty to be forgiving to one another:

It is…a duty of virtue not only to refrain from repaying another’s enmity with hatred out of mere revenge but also not even to call upon the judge of the world for vengeance, partly because a human being has enough guilt of his own to be greatly in need of pardon and partly, and indeed especially, because no punishment, no matter from whom it comes, may be inflicted out of hatred. It is therefore a duty of human beings to be forgiving. But this must not be confused with meek toleration of wrongs, renunciation of rigorous means for preventing the recurrence of wrongs by others; for then a human being would be throwing away his rights and letting others trample on them, and so would violate his duty to himself.[4]

So: Kant argues that we shouldn’t let others trample on our rights—but we also can’t ever punish someone because we hate them, or because we want to take revenge. We should instead be forgiving of others—after all, he points out, we all have our own guilty consciences. Can you make sense of Kant’s example about the last murderer in light of his claim that that “no punishment, no matter from whom it comes, may be inflicted out of hatred?”

Reading  Questions

    1. Compare Kant’s description of punishment (at the beginning of the excerpt) with the modern definition of legal punishment. Are there any differences? If so, what are they?
    2. Go back to the example about Cecile C, the innocent person punished by State X. Now read the definition of legal punishment again. Is the punishment of Cecile actually “punishment” according to that definition?
    3. What do you think about Kant’s argument against fines? Are there other punishments that might affect the rich differently than the poor? If so, do you think Kant’s view would require changing those punishments, too?
    4. Do you agree with Kant that it would be a human rights violation to punish someone more than they deserve, even if that punishment would be extremely useful to society?
    5. What do you think of Kant’s ‘last murderer’ example? How does that example relate to the principle of equality?
    6. Kant’s account, like most retributivist theories, only works if you think people who do morally bad things deserve to suffer. Do you think that is true? If not, why not? If yes, why?


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  1. Mitchell N. Berman, “Punishment and Justification,” Ethics 118, no. 2 (2008): 263, https://doi.org/10.1086/527424.
  2. Excerpted from the English Cambridge edition of Kant’s Metaphysics of Morals. All the emphases are Kant’s. Latin phrases are omitted from the quoted text.
  3. For instance, see Nathan Hanna, “Retributivism Revisited,” Philosophical Studies 167, no. 2 (2014): 479, doi:10.1007/s11098-013-0103-0; Victor Tadros, The Ends of Harm: The Moral Foundations of Criminal Law (Oxford: Oxford University Press, 2013), 59, 61, 63, 78, 86, 102, 190, 308.
  4. Metaphysics of Morals at 6:460-461.