Immanuel Kant (1724–1804) is one of the most influential philosophers of all time. His work was both exemplary of the Enlightenment and, in some ways, deeply critical of it. He made important contributions to all major subfields of philosophy, and few philosophical inquiries since his time have been able to sidestep the questions he raised. Summarizing the work of such a figure may be difficult, but it must be said first that Kant was above all a champion of free inquiry and of the power of human reason. Although he identified certain well-contained topics about which he believed reason was obliged to remain silent, he did not deny its power in any other cases. On the contrary, he affirmed it.

Kant was moreover an ethical individualist who supported free trade, private property, and an objective standard for right and wrong conduct. He looked forward to a future of ever-improving legal regimes that would more and more respect the autonomy and dignity of every human being, and he urged all nations toward a just peace with one another.

In short, Kant was a classical liberal. Not only that, but even in those places where Kant diverged from what we now would call libertarianism, one might argue that he did so in spite of his deeper philosophical commitments, rather than because of them. With the help of further reflection, we might even say that a somewhat better Kantian would be significantly more libertarian than Kant himself ever was. Importantly, Kant’s own system was explicitly open to this kind of development and growth, and it is a mark of his philosophical acumen that he left the door open for those sorts of future improvements.

Let us begin with Kant’s ethics. What is it, Kant asked, that enables us to think about ethical questions in the first place? Can anything be found that conceptually underlies all, or nearly all, claims about morality? In other words, is there a groundwork on which ethics rests? And if we do find a groundwork, how can we know it is objective and lasting?

Kant considered the contemporary answers to those questions unsatisfying. He demonstrated that most other ethical systems rested on what he termed hypothetical imperatives. Hypothetical imperatives are statements of the form “If you want x, you must y.” Statements of this type inevitably derive their moral force from the listener already preferring the stated outcome, x.

Hypothetical imperatives may tell us a good deal about the means to attain a particular end, but they can tell us nothing about, for example, why we have ends in the first place. They also won’t be useful in all times and places. Some people, faced with different circumstances or possessing different values, will not find x a compelling reason to act. How can we ever find common ground, not just with some people, but with all people?

For example, if you want to understand physics, you must study mathematics. But this presupposes that physics is worth understanding. It might be—but if so, why? And for what? Such questions might be answerable, at least for some people, but the sheer fact that we can answer them tells us that physics is not an end in itself. We have answered them only by invoking other ends, and so we must continue our search.

Kant carried this objection to remarkably great lengths: for example, if we want to be happy—a common goal in ethics—then there might be found various courses of action that will make us so. But, Kant argued, happiness in all cases consists simply of getting what we want—so we must be more specific. What is it that we want? And on what basis do we want it? We ought to name the object that we desire, rather than obfuscating about the emotional state that comes from getting it.¹ That is not merely an abstract objection either, because clearly not everyone is made happy by the same things. Some people are even made happy by the attainment of what appear plainly to be wicked things: the murderer who takes pleasure in killing may be motivated by happiness just as well as the poet who takes pleasure in verse. So what is that thing that we should all desire, in all circumstances? What is the thing that it’s never wrong to want?

The answer, Kant said, was a good will. The cultivation of a good will, and the subsuming of all other desires to the development of a good will, was for Kant the work of ethics, the end toward which all other ends pointed. Conscious, rational inquiry about the good was in itself the highest good we might have, and all acts that tended to encourage or manifest a good will were for this reason to be counted good as well.

Crucially, the good will is premised on our capacity for autonomy, a word that Kant used to denote our capacity to set forth ethical rules for ourselves. Ethical agents are all those who seek to supply their own conduct, and their own will, with a reasoned law. Good ethical agents will express and act on the will to impose those laws upon themselves; this project is the one thing that we may, and should, desire as an end in itself. (Kant took yet another step and argued that the human faculty of reason existed for the sake of expressing this ethical law, though that step is not relevant for our purposes, and it is highly contested among philosophers down to the present day, who tend to doubt that nature imbues any faculties with built-in purposes.)

In any case, a truly fundamental ethical law would have at least three important attributes: (a) it would be objective in nature, and thus not subject to arbitrary whims or desires; (b) it would be based on reason alone, and thus intelligible to all ethical agents; and, (c) it would be of a type that we could deliberately subject ourselves to it. As Kant wrote in the Groundwork of the Metaphysics of Morals, “The basis of obligation must not be sought in the nature of man, or in the circumstances in the world in which he is placed, but a priori simply in the conception of pure reason.”² Reason itself would be the groundwork of ethics.

Kant’s ethical theory, then, is neither a consequentialist nor a natural law account, but it is what philosophers call a deontological account. It is not consequentialist, because its laws are not derived from any consideration of what may happen after we attempt to follow them. And it is not a natural law account, or at best it is only very weakly such, because it does not elaborate a theory of human nature on which its morality is necessarily based. Kantian ethics purports to be based on our duty to reason alone. The capacity for reason may be an attribute of mankind, and Kant certainly believed that it was, but reason for Kant is universal and objective and not merely one of mankind’s attributes. As such, no claims about human nature are necessary for Kant’s ethical groundwork to be established, and no changes of time, place, or circumstance can alter it.

A Kantian might even say that natural law accounts that refer to human nature are by this very fact composed of hypothetical imperatives: they all implicitly take the form, “If I am human, then I must … ,” a form that renders them hypothetical. Whatever follows after that statement may be wise practical advice; it may be true for all humans; it may even make the practitioner euphorically happy. But it would not be a fundamental moral law. Ethics must consider, but it must not be founded upon, any such hypothetical imperatives.

Indeed, the agents in a Kantian account of ethics need not be biologically human at all. They must simply be capable of reasoning and of apprehending reason, and desire to give themselves a reasoned law to govern their actions. Such a being could be a space alien, a hyperintelligent computer, or a god, and it would make no essential difference. One potentially appealing feature of Kant’s ethics, then, is that it is open to the inclusion of new species of moral agents, should any be contacted or created in the future. Natural law accounts, and to a lesser extent consequentialist accounts, are not necessarily so open.³

This discussion brings us to a fairly urgent question: What does this foundational moral law look like, anyway? Beginning with the necessity that reason must not contradict itself, Kant arrived at what would come to be known as the first formulation of the categorical imperative—called “categorical” because it was to apply to all ethical agents, in all circumstances whatsoever. It ran as follows:

Act as if the maxim of your action were to become by your will a universal law of nature.⁴

As with all reasoned laws, the moral law must be consistent. As a result, we must be able to will that its maxims should be enacted for all moral agents. If I cannot will that a maxim should apply to all, then I should reject whatever maxim I am considering.

For example, I cannot reasonably will that all people should steal, for this maxim cannot be universalized consistently. It is not merely that a world full of thieves would be a miserable place, although certainly it would be. Rather, theft presupposes the concept of legitimate property ownership, and I cannot consistently will both the existence of legitimate ownership and its occasional, ad hoc violation. We are now able to understand, through reason alone and without appeal to consequence, that the moral principle underlying theft involves a willful contradiction. It must therefore be rejected. Many similar principles of conduct are likewise ruled out, as reflective readers will quickly appreciate.

It is important to remember that the first formulation asks us to consider maxims, or principles, and not individual actions: if I awaken at 6:00 a.m. and eat a bowl of oatmeal, I should certainly not insist that everyone else in the world do exactly the same. But by the first formulation, I must still consider what maxims, if any, lie behind my actions. I might say that the maxims are things such as “strive to be punctual in your work” or “eat so as not to harm the self.” I can readily will, without contradiction, that either of them should be followed by everyone.

Note that I cannot will similarly for those maxims’ opposites. It is not simply that bad consequences would follow from being late or gluttonous, although perhaps they would. The real problem is that attempting to fashion a maxim of either lateness or gluttony would entail setting up an inconsistency somewhere in my maxims. How can it be that I should not arrive to work at the same time when I should? And how could I will to eat in ways that tend to injure the only unquestionably good thing, which is the good will? Neither can be universalized; the first contradicts itself, whereas the second contradicts the cultivation of the good will.

The need for universalization also forbids several things that Kant has often and wrongly been accused of advocating, particularly in libertarian circles.⁵ For example, there can be no possible duty of self-sacrifice purely for the good of others. This is so for at least two reasons. First, such a duty cannot be consistently universalized. Formulating a consistent maxim that would command pure altruism for all moral agents is clearly impossible. The simple reason is that someone else must always exist who will stand as the beneficiary. Of the beneficiary, no comparable sacrifice is asked. And second, to act purely for the anticipated good of another, or for that of a collective, would be to act for a merely consequentialist reason, which is forbidden. As Kant himself wrote:

Benevolent wishes may be unlimited, for they do not imply doing anything. But the case is more difficult with benevolent action … since our self-love cannot be separated from the need to be loved by others (to obtain help from them in case of necessity), we therefore make ourselves an end for others; and this maxim can never be obligatory except by having the specific character of a universal law, and consequently by means of a will that we should also make others our ends… . [But] that one should sacrifice his own happiness, his true wants, in order to promote that of others, would be a self-contradictory maxim if made a universal law. This duty, therefore, is only indeterminate; it has a certain latitude within which one may do more or less without our being able to assign its limits definitely.⁶

In short, Kant condemned unlimited altruism, while recommending a limited, well-reasoned helpfulness. It’s good to be helpful, because one day you too might desire help, and the moral title to help will come from your own fidelity to the maxim of helpfulness. But do not imagine that this maxim is unlimited in scope. We can prove, by sheer logic, that it can’t be.

Kant did, however, reserve a central role for the concept of duty. As we have already seen, actions that outwardly conformed to the moral law were not sufficient to make an agent moral. One must do them because one knows that they are right, and not merely in the hope of securing a gain or avoiding a loss, whether to oneself or to anyone else. Our duty is ultimately an impersonal one, a duty owed to reason alone, and neither to self nor others.

The first formulation can thus be understood as a kind of test for interior moral maxims. These maxims stand to be refined over time as they are reconciled with one another and increasingly clarified. We might even think of the first formulation as describing a sort of ongoing research project, combined with the ethical command that all who are capable of understanding the categorical imperative are by this very fact obliged to continue searching and reasoning.

It may seem, however, that the first formulation gives little clear guidance about politics in particular. Kant’s second formulation of the categorical imperative may help us a bit more:

So act as to treat humanity, whether in thine own person or in that of any other, in every case as an end withal, never as means only.⁷

Closely related to this second formulation is his third formulation:

[E]very rational being must so act as if he were by his maxims in every case a legislating member in the universal kingdom of ends.⁸

Philosophers have puzzled for more than two centuries over precisely what Kant meant in claiming that these three formulations were all restatements of one another. (Unfortunately, Kant never fully explained this claim.) One way of thinking about it may be simply that our maxims will always sooner or later implicate rational beings—at the very least, they implicate our selves—and as a result, they must always proceed from a correct understanding of the attributes of rational beings. If our maxims fail in this regard, they will be inconsistent and thus impossible to universalize. As we honor the ethical search in ourselves, we must do so for others; we must recognize that they are on a similar search to our own. That search requires us to seek and be bounded by universality—and to recognize that all other rational beings should do the same. We are all to consider one another as legislating members in a universal kingdom of ends. Thus, reason and the capacity for reason imbue human beings with a dignity that makes us something more than mere tools or animals.

The political implications now come into sharper focus. In common with Aristotle, Kant held that the search for the good is an end in itself, regardless of where one might find oneself in the search. As a result, we should not use any ethical seeker merely as a tool for our own purposes. Those latter purposes will undoubtedly rest on hypothetical imperatives. By definition, they will be particular to us, in our narrow lives, and thus they will be less important than the quest for the good. In an attempt to fulfill our particular goals, we will have trampled others’ autonomy, which is a necessary part of their search for the good. This we must not do.

Here, then, is the basis (a) for the commonality of human dignity and (b) for laws that treat individuals with an equal initial respect. An Aristotle or an Einstein may be superlatively intelligent, but this intelligence entitles him to no greater share of human dignity—and to no inherent preference in law—when compared with a person of average or below-average intelligence. Those of exceptional talent are not to be accounted supermen, because it is the capacity to undertake the ethical project itself that confers human dignity, rather than any particular attainment along the way.

Now we begin to see how Kant’s ethics might lead to something like libertarianism. Could some baseline set of requirements necessary to treat other persons as ends in themselves—and never merely as a means to some particular end—be instantiated in law, to the exclusion of all other types of law? Such a regime could demand—admittedly perhaps quite often—that individuals refrain from behaving in certain ways; that is, they must refrain from behaving in some of the ways that entail treating others merely as a means to an end. Plausibly, they must refrain from theft of legitimately held property. A fortiori, they must not murder or enslave. They must not deal with one another dishonestly or constrain the free intellectual and moral inquiry of others. And so on.

It is likely not possible to legislate in a way that rules out all violations of the categorical imperative, particularly because, as we have seen, so many of its violations are interior and imponderable. “Did you really act with a good will?” is a question that in many cases we can effectively ask only of ourselves, and even then, we may not have a ready answer. It is also a question we might prefer, on prudential grounds, not to entrust to any external agents.

Still, at least a rough, outward set of prohibitions on the use of other moral agents merely as tools is in many ways congruent to familiar classical liberal aims. A classical liberal might likewise say that the positive duties commanded by the categorical imperative—such as the duty to treat others as ends in themselves—are not capable of being furthered by legislation: if one treats another as an end merely because the civil law has commanded it, then one has certainly not become a more moral person.

The regime in question would potentially face many limits: plausibly, it would never be permitted to order individuals to build a bridge, or go to war, or even pay taxes. Doing so would itself constitute a violation of the categorical imperative, because it would treat the citizens merely as a means toward a greater end, the end desired by government planners. Just as no individual could consistently possess a moral power to command others, so too no government could possess it.

The argument above follows closely the justification that Robert Nozick gave for his own form of libertarianism in his 1974 book Anarchy, State, and Utopia, one of the most important and widely read works of libertarian political philosophy.⁹ It is quite wrong to claim, as some have, that Nozick’s libertarianism was “without foundations.”¹⁰ Nozick’s foundations were Kantian. Regrettably, his treatment of Kant in Chapter 3 of Anarchy, State, and Utopia is fragmented and unsystematic. Nozick generally preferred questioning to expounding, and in this chapter he appears to have presumed a familiarity with Kant’s work that academic philosophers would certainly have, but that libertarian activists perhaps might not. Nonetheless, it can be shown that Nozick began with a Kantian respect for persons as ends in themselves and concluded that this respect would necessarily entail a politically libertarian social order, one with robust negative rights that must not be violated. Let us now recapitulate his argument.

Nozick first drew a distinction in ethics between constraints and goals. Goals are those things that agents try to attain or maximize; constraints forbid certain methods that agents could otherwise use in the pursuit of their goals. Nozick observed that utilitarian moral philosophy concerned itself almost entirely with goals, such as the maximization of happiness, and that utilitarianism generally failed to consider constraints. As a result, utilitarian accounts of individual rights tended to be either lacking or unpersuasive: it is commonly much easier to articulate rights as constraints on other agents’ behavior than as goals to be maximized. For example, one cannot easily quantify the freedom of worship, a step that would be necessary for freedom of worship to be treated as a goal to be maximized by rational agents. Yet it is altogether simple to say that agents shall be morally constrained from coercively imposing a particular form of worship. No quantification is necessary, or even helpful.

Nozick next observed that utilitarianism is commonly thought deficient in that it seems to bless the use of individuals toward its goals in ways that clash with strongly held intuitions. For example, a utilitarian might knowingly punish an innocent man merely to appease an angry mob, provided that punishment would cause more aggregate happiness than abstention.

Common sense would ask us to consider where justice lay in this situation, and a Kantian would claim to have discerned the reason for this commonsense request: the punishment would have been undertaken without a thought to ethical duty, or, in other words, to the universalization of one’s maxim. One can’t possibly will that all innocent people should be punished, or that punishments should always be arbitrary with regard to guilt. Either of those factors would be inconsistent. The only thing one could consistently will here would be that the innocent must never be punished. Utilitarianism would have to operate on inconsistent maxims, in that it would apparently sometimes punish the innocent, in pursuit of the mirage of happiness.

Nozick’s objection to utilitarianism forms a clear parallel with Kant’s objection to similar systems in his own day. Both Kant and Nozick complained in effect that the systems unsatisfyingly rested on merely hypothetical imperatives, like the pursuit of happiness. As a necessary consequence, systems that advocated maximizing happiness as a goal—with no side constraints—would soon bring their advocates to recommend, in effect, using people merely as tools. This is precisely the sort of action that the second formulation most clearly prohibits.

Nozick then speculated on how a society might be set up to prohibit the use of people as tools more generally. He noted that political philosophy is concerned “only with certain ways that persons may not use others; primarily, physically aggressing against them.”¹¹ (Moral philosophy, presumably, would remain free to range across all of human conduct, but in doing so, it would often remain a private endeavor.) But although the scope of political philosophy is narrow, invoking Kant’s second formulation might threaten to eliminate politics entirely. Nozick wrote:

The moral side constraints upon what we may do, I claim, reflect the fact of our separate existences. They reflect the fact that no moral balancing act can take place among us; there is no moral outweighing of one of our lives by others so as to lead to a greater overall social good. There is no justified sacrifice of some of us for others. This root idea, namely, that there are different individuals with separate lives and so no one may be sacrificed for others, underlies the existence of moral side constraints, but it also, I believe, leads to a libertarian side constraint that prohibits aggression against another.¹²

States routinely break this side-constraint. Constantly, in all times and places, states use people merely as tools. Quite possibly they are incapable of doing otherwise. To speak more precisely, the agents of states set goals that they wish to attain, and they compel citizens to try to attain them, the citizens’ dignity and autonomy notwithstanding. States as we know them therefore stand under a severe moral indictment. Far from commanding our respect, our political leaders should be held in contempt. It would seem that the entire point of their existence is to treat people merely as tools and not as moral agents.

Those who wish to defend the actions of the state are thus obliged, as Nozick argued, either to deny all side-constraints (perhaps by denying Kantian moral philosophy itself, and by substituting some more pliable rule); or to offer a different explanation of side-constraints that is less libertarian; or to argue that the individuality and dignity of persons are compatible with initiating coercion against them, a coercion not tantamount to treating them as tools, or things, or beasts of burden. Perhaps we are permitted to treat humans as tools but only in some senses. It is hard to understand, however, how this treatment might be the case without a wholesale denial of the first formulation of the categorical imperative. Failing that, though, a strict Kantian must regard the modern state as illegitimate.

On the whole, Nozick was prepared to accept that outcome, and much of the rest of his book is devoted to proposing and defending visions of social life that did not entail using people as tools. Nozick’s exploration of the alternatives was subtle, thoughtful, and notably attentive to process. That is, he was uniformly suspicious throughout his work of theories that moved quickly toward—or that merely described—a static end state that was to be regarded immediately as just. As we shall see, this attention to process—to history and to development—was another trait he shared with Kant.

Famously, however, in one footnote Nozick did suggest an exception to the need for individual rights understood as side-constraints. Perhaps because that exception is so singular, it has been dear to statists ever since. Nozick wrote, “The question of whether these side constraints are absolute, or whether they may be violated in order to avoid catastrophic moral horror, and if the latter, what the resulting structure might look like, is one I hope largely to avoid.”¹³

We who propose to defend more systematically a Kantian foundation for individual liberty must not avoid Nozick’s question; if we did, it might become yet another “little gap” through which “every man’s liberty may in time go out.”¹⁴

Yet if we are being strictly Kantian, it is unclear exactly how fidelity to the categorical imperative in our political side-constraints could ever cause a catastrophic moral horror to arise—that is, a horror that depends for its existence on our moral commitments alone. Two other possibilities seem much more likely. Although both are awful, in neither of them can we fairly say that our morals are to blame.

The first is that we have made the nonmoral error of proceeding from mistaken hypothetical imperatives. For example: if we wish to prevent plague, then we must punish witchcraft. This is, of course, a terrible mistake, but it is not an error of morality. It is an error of knowledge, because it proceeds from the mistaken belief that witches cause plagues. The categorical imperative can direct us to study such empirical matters, but it cannot supply us with conclusions, no matter how elementary. Those we must find for ourselves.

As reasoning beings who have apprehended the categorical imperative, yes, we are obliged never to knowingly violate it. But merely grasping the categorical imperative does not endow us with all the knowledge needed to act in ways that avert every bad consequence. Nor does it even promise to. The best the categorical imperative can do for us is to command us to learn better and better ways of proceeding, given the constant play of contingency around us. Lived morality may and should be guided by the categorical imperative, but it will always be justified at least partially with reference to hypothetical imperatives as well. And some of them, alas, may be tragically mistaken. None of them is a reason to abandon the categorical imperative itself. Kant himself seems to have been well aware of this fact. He termed the ability to select well among possible hypothetical imperatives prudence, and he saw nothing per se wrong with obeying the counsels of prudence. On the contrary, it was a key part of his moral system.¹⁵

The second possibility occurs when we are mistaken in our belief that a set of events actually constitutes a catastrophic moral horror. Such events may not be catastrophic moral horrors at all, but rather false positives. For example, the social equality of women was once thought a moral horror. And yet today, it looks like one of the clearest possible implications of the categorical imperative itself. If the history of catastrophic moral horrors is any indication, our ability to identify them is far outrun by our propensity to generate false positives. The mixing of the races, love between people of the same sex, in vitro fertilization, vaccination, anesthesia, marijuana, jazz music, and countless others have been characterized, in effect, as catastrophic moral horrors, and none are anything of the kind. Once again, deontological ethics can’t be blamed for these things, because nothing in them is blameworthy.

Before we leave Nozick’s mostly Kantian treatment of libertarian political philosophy, we should admit that Nozick himself had some further qualms. In his book Philosophical Explanations, Nozick appears to have doubted some relevant aspects of Kantianism. Following a suggestion from Walter Kaufmann, Nozick questioned whether Kant’s categorical imperative should be termed categorical at all. Was it not, he asked, just another hypothetical imperative, one bearing the implicit condition to do this if you want to be rational? What if you don’t want to be rational? Nozick asked. “Only a philosopher would think that this is a clincher,” he quipped. “Who else would think that the ultimate insult is to be called irrational?”¹⁶

Various ways exist to escape this difficulty. One of the simplest is to point out that any interlocutors proceeding along these lines would in so doing have forfeited their claim to our reasoned consideration. Persons who deliberately renounce reason are not entitled to give us their reasons and expect us to pay heed to such reasons. Because such people have declared that they are not deploying reason, no useful conversation can take place between us. Still less may they legislate for those of us in the kingdom of ends, of which they claim they are not even a part.

Let us now return to Kant, who was not so politically radical, even if Nozick’s work suggests that he should have been. Kant’s own politics were a distinctly moderate classical liberalism, one that even approved of involuntary taxation, on the grounds that it alone made civil society possible. Kant’s political theory included a significant social contract aspect, but it was also sensitive to the fact that human societies are subject to change in the course of history, for either better or worse. Kant viewed it as the ongoing task of enlightened philosophy to gradually ameliorate the defects found in the societies of his day. Modern libertarians are apt to find his approach deficient, but among the deficiencies, they will find much to praise and to ponder.

In keeping with his ethical thought, Kant proclaimed that the supreme principle of law should be as follows:

Every action is right and just, the maxim of which allows the agents freedom of choice to harmonize with the freedom of every other, according to a universal law.¹⁷

We can immediately appreciate that the preservation of practical choice—which allows the prospect of social harmony—was central to Kant’s conception of justice. He moved from this principle very quickly to a formula quite resembling the later law of equal freedom, variants of which are found in Herbert Spencer, John Stuart Mill, John Rawls, and others. As Kant wrote:

So act that the use of thy freedom may not circumscribe the freedom of any other.¹⁸

The formula is not as capacious as Spencer’s, who accorded each individual the maximum liberty compatible with a like liberty in others. But we can discern here a sharp distinction, as is common in the classical liberal tradition, between liberty, which is respectful of the same in others, and license, which is not. But why do laws exist that are socially enacted and thus (obviously) exterior to the will? Kant’s answer reveals much about his social theory in general, and particularly that theory’s evolutionary character:

The very notion of law consists in that of the possibility of combining universal mutual co-action with every person’s freedom.¹⁹

Law exists to facilitate cooperation—but only on the condition that we do not at the same time obliterate anyone’s freedom. Law exists not to achieve a given outcome in society but to allow both voluntary cooperation and individual liberty, with which many different projects might be realized.

In his “Idea of a Universal History from a Cosmopolitan Point of View,” Kant even suggested that both freedom and cooperation were necessary for mankind to achieve its destiny as a species—an idea that we can forgive our readers for shrinking from, at least at first. It certainly sounds profoundly unlibertarian. Yet on closer examination, the destiny that Kant imagined may not be so threatening. What Kant had in mind by the destiny of the species may even resemble what F. A. Hayek termed a spontaneous order:

The means which Nature employs to bring about the development of all the capacities implanted in men, is their mutual Antagonism in society, but only so far as this antagonism becomes at length the cause of an Order among them that is regulated by Law.²⁰

It is irrelevant whether “Nature” causes this order to emerge, or whether the order emerges of its own accord, or even whether those two possibilities are just different ways of saying the same thing. What is key is that mankind can develop to the fullest only in the context of an ongoing social order, one that lasts across many lifetimes and permits a measure of peaceful competition. One form of peaceful competition will spring to mind immediately for classical liberals, namely, the market process. Others, however, do exist, and it is worth inquiring how at least two social systems, the market order and socialism, might fare from a Kantian perspective.²¹ Let us consider Kant’s attitudes toward the market process, or at least what we can infer about them, before moving on to what a Kantian libertarian might have to say. Following that, we will consider some of the objections of a Kantian socialist.

One cannot properly belong to the classical liberal tradition without a robust account of private property that entails its relatively unrestricted usage and transfer. To be called liberal in any sense, this account must also give solid reasons to reject a similar usage and transfer of persons. And indeed, Kant had just such an account. Kant’s theory of the institution of property was in many ways more historically grounded than Locke’s, or even Hume’s. It also sat well with the intellectual and ethical project we have outlined above—the gradual apprehension of the ethical laws of reason, and the reconciliation of the will to reason’s dictates.

Kant believed that property rights typically arose gradually, out of repeated claims, counterclaims, adjudications, and reaffirmations, rather than from any one definitive act of settlement or assignment, whether by the state or by individuals.²²This process-oriented view helps us gain new perspective on several vexing problems, including compensation for historical wrongs. It may prove, for example, that, contrary to the common-law maxim concerning improperly acquired property, legitimacy can arise over time. Given the initially arbitrary (and often criminal) origin of nearly all title to land, there is no other way forward in any case. We must either concede that all the world is stolen, after which we must establish an institution to redistribute everything, or we admit that past errors are better corrected gradually. Institutions that redistribute everything are too dangerous in practice ever to be trusted, and thus our choice becomes clear.

From an unowned condition, land in Kant’s theory might first be appropriated by anyone with the means to defend it. No mixing of labor was required to stake a claim. This provisional claim, however, was in no sense an absolute right. In this Kant differed from Locke in two ways. Locke, recall, would insist that the mixing of labor was necessary to establish ownership. And from that point on, Locke held that ownership was settled and absolute.

On neither point would real life appear to correspond well to the Lockean account. On both, Kant’s account seems to describe initial appropriation with greater historical accuracy. There is at best a limited obligation not to interfere with land that is in this manner only provisionally controlled by others. But this obligation may be breached if a land claimant refuses, for example, to enter into a state of civil society with his neighbors. It will not do to have barbarians on our borders. Indeed, this very consideration brought Kant to believe that implementing a social contract was morally obligatory, that contract’s relative justness notwithstanding. Anything at all would constitute an improvement over the lack of civil society.

This move is certain to be rejected among libertarians, but it is unclear to me how foundational it is to Kant’s social thought. After all, contracts of this type may be exceptionally rare.²³ In any case, the provisional obligation to respect property rights solidifies with the entry into civil society, which rational beings should recognize as desirable. It solidifies further with time and usage under a just regime of laws.²⁴ As the modern scholar Marcus Verhaegh has written:

The best metaphor for Kant’s account of movement out of the state of nature is one of disarmament—staged, negotiated disarmament. We are all duty-bound to reduce violent conflict and the potential for violent conflict by moving toward a scenario in which ownership disputes are decided by the rule of right law, rather than ongoing, competing military power. But prior to full disarmament—the fully cosmopolitan globe—military force plays a significant role in setting the bounds of right ownership.²⁵

Alas, military force is still necessary. And it would remain necessary, Kant believed, until a worldwide regime of perpetual peace had been established, one in which all countries enjoyed a republican form government, as well as the renunciation of war and standing armies. This cosmopolitan social order would be one of the crowning achievements of human civilization. Kant also thought it would take many generations to accomplish. In the meantime, governments should do their best to move toward it.²⁶

In contrast to his strong claims about the interior necessities of reason, Kant was relatively modest in his claims about the nature of history and its unfolding. He did not claim to have discerned a set of historical laws that will operate as of necessity, even if, at first glance, he may seem to have done so, and thus to stand condemned as a historicist. On the contrary, Kant was deliberately vague about the institutions of the future cosmopolitan society, which neither he nor any of us could discern in their entirety. Unlike Marx or Hegel, Kant also left room for—and indeed assigned a central place to—the liberty of individual action, which will, if allowed to operate, eventually instantiate the cosmopolitan society of the future. The active agents here will be free individuals, not social classes, national spirits, or impersonal social forces, and the claims that Kant made about the future were few and qualified.

How then do property rights and cosmopolitan law relate to Kant’s ethical project? Neither will necessarily make us good people; nothing prevents the propertied individual from having a bad will. Nor are property rights even necessary for possessing inward ethical freedom, for one always has the capacity to will the good—or not—regardless of how unfree or poor one may be. A good person may live, and be good, under a bad government, or in destitution. The traits are in this sense quite independent.

But property rights in things alone—and never in persons—can help us obey more perfectly the negative duties that are most clearly implied by the second formulation of the categorical imperative: by granting individuals each the capacity to acquire, modify, and alienate property, we also allow them to use property to their own ends, and we declare, as it were, our maxim that only unreasoning things are to be used as tools—and never people. A cosmopolitan regime of private property that excludes slavery thus draws a bright line between the kingdom of ends, which is reserved for people, and the kingdom of means, which largely overlaps the legal category of property. This outward conformity, Kant believed, could lead people to the inner apprehension of the moral law.²⁷

Under a cosmopolitan, property-holding regime, we likewise obtain a similar type of outward autonomy for ourselves. Much of the cosmopolitan project seems aimed at making the outside more closely resemble the inside. It aims at expanding our freedom of action in the phenomenal world, that is, the world of exterior experiences, to more closely resemble the freedom of action in the interior world of the mind. What we do with our property, do note, may be good or bad, but we will at least have secured one of the foundations of leading a morally good external life, which is the capacity for self-rule. (For Kant, the growing capacity for an adult-like self-rule, a rule independent of the state, was also the essence of the Enlightenment.²⁸) Under free institutions, obedience to the written law and obedience to the moral law may now begin to harmonize, even if, as Kant warned, our current property claims may not be fully settled or just. In time, they can be, if only we continue to will it.

So far, we have said much about property ownership but little about trade. A classical liberal might even wonder, hereabouts, what the point of ownership might be, if it were not that ownership allowed for transfer and for the market process to operate. Our silence, though, is for a fairly strong reason: Kant himself would appear to have cared little for economics. He rarely deployed examples that proceeded from what we might term economic behavior in the narrow sense, that is, those involving buying and selling. His thoughts on the matter would appear to have been few, and we are left to draw inferences from a meager data set.

When Kant did write about market exchange, however, he certainly did not write to condemn the practice in all cases. Instead, he condemned only specific types of exchange, including instances of fraud; price discrimination; and the sale of organs, such as teeth, a common practice at the time. (Of those three, it is not at all clear that the last two condemnations must stand.) Kant was also aware of the writings of Jean-Jacques Rousseau, who did condemn commerce, often quite explicitly, and it is evident that although Kant had every opportunity, he declined to agree.

In all, however, much work remains to be done in theorizing the market process from the standpoint of Kantian ethics. Important groundwork has been laid by the contemporary philosopher Mark D. White, who suggests that Kant’s negative duties—those things that we are obliged, in an absolute sense, to refrain from doing to others—and Kant’s positive duties—those things that we are obliged, in a limited sense, to do out of benevolence to others—are both compatible with a market society. The former make a market society possible, and the latter make it agreeable. White has even loosely paralleled these two types of duties with the worlds described in Adam Smith’s two great works, The Wealth of Nations and The Theory of Moral Sentiments. The former considers the realm of merely negative duty, whereas the latter examines our positive duty of beneficence. Although Smith’s ethics were not deontological like Kant’s, the approach still seems promising.²⁹

Against all this, however, it has sometimes been suggested by socialist students of Kant’s ethics that the categorical imperative actually forbids all, or at least many, market exchanges. In buying and selling, do I not treat my counterpart merely as a means to an end? Have I not made a mere object of the baker? Have I not treated him precisely as I might have treated a vending machine, which is undoubtedly a tool? (It hardly seems that the scripted, almost mechanical conversations that take place in the course of a typical business transaction would constitute much of an improvement, then, over someone talking absentmindedly to a vending machine!) Things seem to stand even worse in regard to the buying and selling of labor, in which the capitalist would appear to weigh the choice to employ a laborer against the choice to “employ” a machine, one that might constitute, for his purposes, a perfect substitute. Is this not a fatal flaw in the project of justifying the market process in Kantian ethics?

If it were a flaw, then the fact that market exchange would seem necessary to us would indicate no more than a failure of our own will, with the corresponding need to rectify it. Perhaps we must even resign ourselves to the catastrophic moral horror of advocating socialism (which, we would have to concede, we had misclassified). So might say Kantian socialists and some others.³⁰ Indeed, no less an authority than Ludwig von Mises argued that “out of Kant’s mysticism of duty … it is easy to trace the development of socialist thought.”³¹

Readers should already appreciate that Kant’s allegiance to duty was at least not openly mysticism, even if they do not follow or agree with his argument. At no point does Kant appeal to the unknowable or to a higher mind; the appeal is, purportedly, to one’s power of reason alone. There are several further reasons why Mises was simply wrong in this passage, and why Kant’s cosmopolitan social order need not be—and perhaps should not be—a socialism.

First, as Kant himself argued, the only perfect duties that we owe to other autonomous moral agents—that is, the only duties that are absolute, or categorical—are negative in character. They are actions that we must be certain of refraining from. We have already seen that we do not have a perfect duty to help others, much less to provide them with any particular set of resources, categorically and without regard to circumstance. Kantian socialists must therefore reckon with the fact that all forms of nonvoluntary socialism will entail duties of exactly this improper type. In common with every other form of modern state, socialist states necessarily use people as tools.

Second, for Kant himself, the provision of economic goods appears to have been a matter not of ethics but of prudence and skill. The question of which economic system—(a voluntary) socialism or (a voluntary) capitalism—would best supply the world’s material needs, is not therefore a matter to be settled with reference to the categorical imperative alone. Rather, economic science can and should settle it independently, albeit guided by the side-constraints that arise from the imperative.

Third, we should consider reciprocity: If I am treating the baker as a tool—well, is he not doing precisely the same to me? Does he not treat me as a means of getting rid of his surplus bread? Might I just as well be replaced by a purchasing machine? Maybe so. But how can it be that we both treat each other merely as tools? If I am treated as a tool, then I am robbed of my autonomy. But if I am robbed of my autonomy, how can I also treat my counterpart, who allegedly masters me, as a tool? It is hard to see how I can act in the ethical sense at all, let alone act badly, when I have been deprived of my agency. The presence of reciprocity, then, suggests that neither party’s will has been violated by the other.

Fourth, if we grant that market exchanges treat at least one agent involved merely as a tool, how do we differentiate market exchanges from nonmarket forms of cooperation, which seem to stand similarly accused? In what sense do participants in a voluntary socialism not treat one another as merely a means to an end? The categorical imperative does not require us all to live as hermits; indeed, Kant enthusiastically recommended cooperation of many different kinds.

We must now look for some way to formulate the essential act of cooperation that does not depend on maxims that fall victim to the categorical imperative. Note that it will not suffice simply to say that our cooperative dealings concern only the disposition of tools, and that, as a result, only hypothetical imperatives are in play. The very question at hand is whether we have impermissibly treated our counterparts in the exchange as tools in themselves.

Cooperation of all types might be said to take the following form, whether in the market or out of it: together, two autonomous agents agree to formulate a plan, according to which they will use their combined resources. Both agents equally desire that the plan be enacted over any available alternatives. Given that the plan represents each agent’s first choice, it would appear difficult to claim that the plan does not represent what the participants will. Note that this conclusion holds true whether or not a market exchange has taken place; note also that both buyer and seller get their first choice of all available options, even when the sale does not go through.

In this reconstruction, a vending machine is still a tool, but it is a tool that both buyer and seller agree to use together to realize an agreed-upon distribution of resources. A baker is still an autonomous agent, one who proposes a plan of action to all who enter his shop. And a capitalist, who must choose between human labor and machine labor, does not necessarily treat a laborer merely as a machine. Rather, he chooses between two different plans, both of which at various points entail human beings voluntarily working for pay: either the laborer does it directly, or else the laborer(s) who made the machine play that role indirectly. In every case, there is a cooperation of wills.

Much work remains to be done here, in part because of modern classical liberals’ deep aversion to Kantian ethics and in part because of Kant’s neglect of economics. But the Austrian school owes much to Kant in spite of this neglect, above all in epistemology. As a result, the project of further reconciling Kant’s ethics to libertarianism is likely to prove fruitful to scholars who are so inclined.

The project will not always be easy. Kant flatly denied one right that classical liberals have generally emphasized, the right of resistance to the state. But as with the question of whether one may compel obedience to an initial social contract, it is possible to argue that Kant’s dismissal of the right of resistance is a peripheral part of his social thought. Is it really, as Kant thought, always the subject who has broken the social contract? And never the state? A contract that one party is incapable of violating would be highly unequal, and might even violate the categorical imperative. A better Kantian should perhaps reject it out of hand, exactly as Robert Nozick did.

Finally, freedom of expression played a special role in Kant’s social theory. Whereas modern libertarians are apt to collapse the freedom of expression into simply another aspect of one’s property rights—albeit perhaps a psychologically important one—for Kant, the ability to exercise one’s reason publicly as it regarded current affairs and government was more than a special use of one’s property. It was also a key part of living in a civil society. The capacity was vital for two reasons. First, Kant believed that it was the citizens’ only substantial defense against the sovereign power in cases where the sovereign acted wrongly. And second, good government itself could arise only through a process of deliberation, in which all views were heard, candidly and without fear of punishment.

Now, we need not hold, as Kant did, that individuals have no proper right of revolution against a sovereign in order to believe that the right to air our grievances commands a special status in a governed society, as opposed to a stateless one. Even a slight regard for consequence will allow us to reach that conclusion anyway. This regard for consequence may not form any part of the groundwork of the moral law. But it is also not forbidden by the moral law, and entrance into civil society may require it in the manner of a hypothetical imperative.

Much work remains to be done in grounding libertarian social thought in Kantian ethics, but it is clearly a viable and ongoing project, one that already promises to free libertarian social thought from many of the problems that have beset it in certain of its other formulations.

1. See Julie Lund Hughes, “The Role of Happiness in Kant’s Ethics,” Aporia 14 (2004): 61–72. As Kant wrote, equating good with pleasure “is opposed even to the usage of language, which distinguishes the pleasant from the good, the unpleasant from the evil, and requires that good and evil shall always be judged by reason, and, therefore, by concepts which can be communicated to everyone, and not by mere sensation, which is limited to individual subjects.” Immanuel Kant, “Critique of Practical Reason,” in Kant’s Critique of Practical Reason and Other Works on the Theory of Ethics, 4th rev. ed., trans. Thomas Kingsmill Abbott (London: Longmans, Green and Co., 1889), p. 111, http://files.libertyfund.org/pll/pdf/Kant_0212_EBk_v7.0.pdf. Note also that I have preferred online, public domain translations because of their easy availability. ↩
2. Immanuel Kant, “Fundamental Principles of the Metaphysic of Morals,” in Kant’s Critique, p. 29. Note that the title of the Groundwork is here translated as “Fundamental Principles … .” ↩
3. This appeal to a transhuman form of reason is entertained more or less explicitly in “Fundamental Principles of the Metaphysic of Morals,” in Kant’s Critique, p. 51. ↩
4. Immanuel Kant, The Metaphysics of Ethics, 3rd ed., Henry Calderwood, trans. J. W. Semple (Edinburgh: T. & T. Clark, 1886 [1796]), p.34, http://oll.libertyfund.org/titles/1443#kant_0332_338. ↩
5. Ayn Rand famously despised Kant. It may be that her quarrel with Kant arose not from his ethics or politics, but from his metaphysics and epistemology. This analysis, although plausible, would sit badly with the few relatively clear places in which Rand attempted to critique Kant; in them, she makes primarily ethical objections. Metaphysical and epistemological concerns, meanwhile, are beyond the scope of our inquiry. ↩
6. Kant, “Critique of Practical Reason,” p. 199; just previously, on p. 198, Kant insisted that our own perfection was a duty of a similar type. A field opens up for the practice of virtue, one that is governed neither by pure altruism nor by pure egoism, for both of those extremes are logically untenable. ↩
7. Kant’s Critique, p. 68. ↩
8. Kant’s Critique, p. 75. ↩
9. Robert Nozick, Anarchy, States, and Utopia (New York: Basic Books, 1974). ↩
10. See Thomas Nagel, “Libertarianism without Foundations,” Yale Law Journal 85 (1975): 136–49, http://www.jstor.org/stable/795521?seq=1#page_scan_tab_contents. ↩
11. Nozick, Anarchy, p. 32. ↩
12. Ibid., pp. 33–34 [emphasis in original]. ↩
13. Ibid., p. 30. ↩
14. John Selden, cited in F. A. Hayek, The Constitution of Liberty (Chicago: University of Chicago Press, 1960), p. 205. ↩
15. Kant writes, “Hence it follows that the imperatives of prudence do not, strictly speaking, command at all, that is, they cannot present actions objectively as practically necessary; that they are rather to be regarded as counsels (consilia) than precepts (præcepta) of reason, that the problem to determine certainly and universally what action would promote the happiness of a rational being is completely insoluble, and consequently no imperative respecting it is possible which should, in the strict sense, command to do what makes happy.” We may pursue happiness, but we must not understand this pursuit to be based on a categorical command. Kant, Fundamental Principles of the Metaphysic of Morals, p. 47. ↩
16. Robert Nozick, Philosophical Explanations (Cambridge, MA: Harvard University Press, 1981), p. 354. But he had qualms upon qualms; the imperative that Nozick settles on, some hundred pages later, nonetheless has an admitted “kinship” to Kant’s, and it’s a fair question whether Nozick did not in fact slouch back to a restatement of the categorical imperative. See p. 462. ↩
17. Immanuel Kant, The Metaphysics of Ethics, 3rd ed., ed. Henry Calderwood, trans. J. W. Semple (Edinburgh: T. & T. Clark, 1886 [1796]), http://oll.libertyfund.org/titles/1443#Kant_0332_338. ↩
18. Ibid., p. 179. ↩
19. Ibid., p. 180. ↩
20. Immanuel Kant, “Idea for a Universal History from a Cosmopolitan Point of View,” 4th proposition, in Kant’s Principles of Politics, Including His Essay on Perpetual Peace: A Contribution to Political Science, trans. William Hastie (Edinburgh: T. & T. Clark, 1891 [1784]), http://oll.libertyfund.org/titles/358#Kant_0056_39. ↩
21. Competition is indeed possible under socialism, albeit outside the market process. Competitions in the arts, athletics, and the like certainly have existed under socialist regimes. Whether they are preferable to their capitalist counterparts is a question we need not explore, though I suspect that socialists may be thankful for our silence. ↩
22. This summary closely follows Marcus Verhaegh, “Kant and Property Rights,” Journal of Libertarian Studies 18 (Summer 2004): 11–32. ↩
23. See Kevin E. Dodson, “Autonomy and Authority in Kant’s Rechtslehre,” Political Theory 25 (February 1997): 93–111. ↩
24. Verhaegh, “Kant and Property Rights,” p. 20. ↩
25. Ibid., p. 21. ↩
26. Kant’s vision of a gradual transition—from violent appropriation defended violently toward a cosmopolitan civil society defended by reason alone—anticipates much of subsequent German liberalism, particularly the anarcho-capitalist vision of the early 20th-century sociologist Franz Oppenheimer. Oppenheimer’s “free citizenship” bears a strong resemblance to—and would seem to share all the essential qualities of—Kant’s cosmopolitan law, with the sole exception that Oppenheimer believed in the eventual obsolescence of government itself. Thus, although it is not often appreciated today, a significant strain of market anarchism was directly inspired by Kantian social theory. See Franz Oppenheimer, The State: Its History and Development Viewed Sociologically, trans. John M. Gitterman (Indianapolis, IN: Bobbs-Merrill, 1914; repr., London: Forgotten Books, 2012). ↩
27. That is, Kant did not really think that external conformity to the moral law was completely valueless. Although it could not be called ethically foundational, external conformity did have a didactic and instrumental value. In the second section of the Critique of Practical Reason, Kant described a method of teaching ethics that began with commonsense intuitions about ethical actions and motivations and proceeded socratically toward the categorical imperative. Along the way, the student would learn to distinguish merely outward conformity from the goodness that inheres in the good will. It is evident that properly formulated laws could aid considerably in following this method. Kant, “Methodology of Pure Practical Reason,” in Critique of Practical Reason, pp. 209–17. ↩
28. Immanuel Kant, “What Is Enlightenment?” trans. Mary C. Smith [1784], http://www.columbia.edu/acis/ets/CCREAD/etscc/kant.html. ↩
29. See Mark D. White, “Adam Smith and Immanuel Kant: On Markets, Duties, and Moral Sentiments,” Forum for Social Economics 39 (April 2010): 53–60. See also Mark D. White, Kantian Ethics and Economics: Autonomy, Dignity, and Character (Stanford, CA: Stanford University Press, 2011). ↩
30. The signal figure for this interpretation of Kant is Hermann Cohen, though it must be conceded that it seems to suggest itself almost immediately to all libertarian skeptics of Kantianism. Hermann Cohen, Ethik des Reinen Willens (Berlin: Bruno Cassirer, 1904; repr. Charleston, SC: Nabu Press, 2010). ↩
31. Ludwig von Mises, Socialism (Indianapolis, IN: Liberty Fund, 1981), p. 388. Mises’s analysis of the Kantian socialist Hermann Cohen is insightful and correct, I believe, but I do not agree that Kant should share the blame, for reasons that will soon become clear. ↩