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.