Kant's most successful attempt to solve these two problems appears not in the Foundations but in the Metaphysics o f Morals for which the earlier work is intended as a foundation or groundwork. Before turning to that text, however, it might be worth pausing for a moment to observe the relationship between the unresolved problems just stated and the work of the most prominent contemporary political theorist, John Rawls. In his widely read work, A Theory of Justice, Rawls undertakes to demonstrate that rationally self-interested individuals, placed in a situation designed to mimic that of noumenal agents, will necessarily choose to commit themselves to a set of general principles regulating the basic structure of any society of which they may be members. By virtue of the conditions of deliberation - characterized fancifully by Rawls as consisting in a "veil of ignorance" - the choices made by these individuals will be universal and necessary, hence objective, and will at the same time be sufficiently specific to yield substantive social imperatives.
Rawls' treatment differs fundamentally from that of Kant, of course, inasmuch as Rawls posits rationally self-interested, which is to say in Kant's language heteronymous, individuals. Nevertheless, as Rawls has refined and revised his theory, he has moved more and more in the direction of a Kantian reinterpretation of his central ideas. Rawls' theory is a good deal more technically sophisticated than Kant's, involving as it does notions drawn from modern neo-classical economic theory and the branch of mathematics known as Game Theory. But, not surprisingly, Kant's theory is a great deal more profound than Rawls', for whereas Rawls posits a society of rationally self-interested agents, thereby giving up entirely any attempt to identify unconditional principles of morality, Kant holds firm to the idea of rational agents as such, abstracting even from their self-interest, and appealing only to what can be derived from their character as agents, which is to say from the fact that they possess practical reason.
II. The Resolution of the Problem in the Rechtslehre
It is in Part I of the Metaphysics o f Morals, the "Theory of Right" or "Theory of Justice" [Rechtslehre] that Kant finally mounts a full-scale frontal assault on the problems left unresolved at the end of the Foundations. This fact - assuming for a moment that my reading of the situation is correct - has a very interesting significance. Contrary to Karat's own conception of the relationship between his moral and political theory, it would appear that they are not separate and co-equal branches of the Metaphysics of Morals. Rather, they are a single integrated theory, in which the central thesis of the political theory is required to complete the argument of the moral theory. In this regard, it is suggestive to compare Kant both with Rousseau, who influenced him, and with Rawls, whom he in turn influenced.
Kant begins the Rechtslehre by introducing the concept of justice. In a section entitled "What is Justice?" he writes:
The concept of justice, insofar as it relates to an obligation corresponding to it (that is, the moral concept of justice), applies [only under the following conditions]. First, it applies only to the external and - what is more - practical relationship of one person to another in which their actions can exert an influence on each other (directly or indirectly). Second, the concept applies only to the relationship of a will to another person's will, not to his wishes or desires (or even just his needs), which are the concern of acts of benevolence and charity. Third, the concept of justice does not take into consideration the matter of the will, that is, the end that a person intends to accomplish by means of the object that he wills; for example, we do not ask whether someone who buys wares from me for his own business will profit from the transaction. Instead, in applying the concept of justice we take into consideration only the form of the relationship between the wills insofar as they are regarded as free, and whether the action of one of them can be conjoined with the freedom of the other in accordance with a universal law.
Justice is therefore the aggregate of those conditions under which the will of one person can be conjoined with the will of another in accordance with a universal law of freedom.
Thus, as Kant states two paragraphs later, "the universal law of justice is: act externally in such a way that the free use of your will is compatible with the freedom of everyone according to a universal law."
Kant glosses this, almost immediately, as follows:
[T]he concept of justice can be held to consist immediately of the possibility of the conjunction of universal reciprocal coercion with the freedom of everyone. Just as justice in general has as its object only what is external in actions, so strict justice, inasmuch as it contains no ethical elements, requires no determining grounds of the will besides those that are purely external, for only then is it pure and not confused with any prescriptions of virtue.
There are a number of problems in Kant's doctrine here, arising principally from his insistence on speaking as though the distinction between the noumenal and the phenomenal [or the internal and the external, as he puts it here] can actually be drawn within experience. All such claims, implicit or otherwise, are, of course, strictly incompatible with the teaching of the First Critique. The real difficulty for my present purposes is the fact that this conception of justice as justified universal reciprocal coercion does not provide the unconditional a priori substantive content for moral principles for which we are searching.
The problem, very simply, is that despite the appearance of Kant's formulation, which is cast in categorical language, the injunction is still hypothetical. IF you choose to coerce others, THEN you yourself must submit to a like coercion. Note, by the way, that it is as yet unclear how narrowly this injunction constrains us, even should we choose to coerce. It would appear that there is a very wide range of reciprocal coercions compatible with the injunction, including some that Kant would presumably not find attractive. For example, would his principle be compatible with a system of laws that authorizes blood feuds and duels?
But even if Kant can demonstrate that a group of individuals, by committing themselves to the fundamental principle of justice, thereby so severely constrain their subsequent legislative choices that only a single system of laws is compatible with that principle, that system will still have a merely hypothetical status, for it will command only those who have chosen to enter into the social contract. What Kant needs - what he has needed from the very start - is an argument designed to show that failure to enter a social contract can only issue from an internal contradiction in willing. In short, Kant must show that a rational agent as such necessarily seeks to enter into a social contract, and does so as soon as possible.
To return for a moment to the failed example of false promising from the Foundations, if Kant could show that the institution of promising is required by the fundamental principle of justice [not, one would imagine, too difficult a task], and if Kant could also show that a rational agent as such necessarily enters a social contract, then he could conclude that rational agents as such are not only, in all consistency, required by mere reason alone to keep such promises as they make, but that they are also required, by the dictates of a priori reason, to adopt the practice of promise-making. He then really could conclude, as he wishes to, that false promising is an example of contradictory willing all the way down.
I do not believe that Kant accomplishes these extraordinary tasks. If I did, I would, in all consistency, forthwith embrace his ethical theory. But I think I can show that he makes an extremely imaginative stab at the second of them in the Rechtslehre, where, as I shall suggest, he advances an argument designed to show that we have an unconditional obligation to enter a social contract.
The key to his argument is the concept of property.
An object is mine de jure (meum juris) if I am so bound to it that anyone else who uses it without my consent thereby injures me. The subjective condition of the possibility of the use of an object is possession.
An external thing is mine, however, only if I can assume that it is still possible for me to be injured by someone else's use of the thing even when it is not in my possession. Consequently, there would be a self-contradiction in the concept of possession if it did not have two meanings, namely sensible possession and intelligible possession- Sensible possession means the physical possession of an object, whereas intelligible possession means the purely de jure possession of the same object.
Kant goes on to discuss the distinction between sensible and intelligible possession in ways that are thoroughly problematic, involving as they seem to the legitimacy of a distinction between the phenomenal and the noumenal within experience. We can leave that difficulty aside for our purposes, for it is of course the concept of intelligible possession, or possession de jure, that is relevant. Almost immediately, Kant states what he calls the Juridical Postulate of Practical Reason, which asserts that "it must be possible to have any and every external object of my will as my property." In other words, as Kant explains, "a maxim according to which, if it were made into a law, an object of will would have to be in itself (objectively) ownerless (res nullius) conflicts with Law and justice.”
Before analyzing how Kant justifies this postulate, and uses it to accomplish his fundamental aim in his moral theory, it is worth pausing to remind ourselves just what is being claimed here, for a great deal of contemporary importance is at stake. It is not too much to say that Kant is here laying the groundwork for the refutation of all manner of environmentalist and ecological doctrines, as well as a number of nationalist doctrines based upon a conception of the objectively privileged territory, homeland, or place of a people. Kant himself, of course, is looking backward, not forward. His intention is to destroy the last vestiges of feudalism, and lay the groundwork for a thoroughly rational commodification of natural objects.
What the principle says is that anything can, in principle, be someone's possession. There is nothing unownable. It does not follow, needless to say, that everything is actually owned; only that there is nothing - no tree, no river, no plot of land, no species of animal or plant, no planet, no solar system - that by its nature resists ownership, that is such that it cannot be the rightful possession of some individual or group of individuals. And possession here implies rightful use of the possessed thing, by the owner, in pursuit of the owner's purposes, and also alienation or legal transfer of the possession of the possessed thing to another rational agent.
Needless to say, this conception flies in the face of the pre-capitalist traditions against which Kant is arguing. To suggest that the Earl of Northumberland owns Northumberland, and can sell it to the King of France, should he choose, is fundamentally to undermine the notion of hereditary family possession implied in the familiar allusion to the Earl as simply "Northumberland," as in one of Shakespeare's plays. Donald Trump, on the other hand, can perfectly well sell the Trump Shuttle to Delta, should he find himself a bit short of cash.
In a more modern vein, any suggestion that the human race stands in a symbiotic, or fiduciary, or other moral relationship to nature is completely incompatible with Kant's Postulate. Equally incompatible, of course, is any form of religious or quasi-religious privileging of species or things other than the human species or other species of rational agents, should they exist. In the coin of Kant's Realm of Ends, the principle "Treat humanity always as an end, and never simply as a means" is inscribed on the obverse. On the reverse, however, is found the correlative principle, "Anything else may be treated as a means only."
Kant now offers an extremely strong interpretation of the concept of intelligible possession. "A thing is externally mine," he says, "if it is such that any prevention of my use of it would constitute an injury to me even if it is not in my possession (that is, I am not the holder of the object)." What Kant is speaking of here, as he indicates immediately, is intelligible possession, or de jure possession. The language might lead us to conclude that Kant is deliberately trying to construct a justification for the most thoroughgoingly unregulated period of capitalist expansion, but that would be a trifle hasty, I think. Kant's Postulate is perfectly compatible with positive legislation to constrain the ways in which property owners deal with their property - zoning laws, and so forth. What the Postulate says is that all such laws must be acts of a legislature constituted by a social contract. They cannot be deduced, independently of legitimate legislation, from the nature of the objects themselves. It is not that an owner must be allowed to do with his or her property whatever he or she wills, but that such freedom must at least be possible, in order for there to be de jure possession.