The argument that self-ownership entails voluntary slavery is as follows. If individuals possess the right to exclusively control the use of their person, then they also possess the right to voluntarily transfer the right of exclusive control to another person. To transfer this right would be to transfer one’s ownership of one’s self. To be owned by another is to be a slave. Therefore self-ownership entails voluntary slavery.
The standard Anarcho-Capitalist response to this argument is to deny the possibility of voluntary slavery. I shall consider two attempts at doing so. Firstly, it is argued by many Anarcho-Capitalists that slavery is by definition involuntary and so to speak of ‘voluntary slavery’ is to speak of an empty category and to utter contradictory nonsense. The problem with this line of argument is that the initial argument is not that self-ownership entails voluntary involuntary ownership of one human being by another, but rather that self-ownership entails the voluntary ownership of one human being by another. The fact that involuntary ownership of one human being by another is involuntary is entirely consistent with the possibility of one human being owned by another voluntarily. Thus to insist that slavery is by definition involuntary is to ignore the referent of the term ‘slavery’ in this instance and to respond to an obvious straw man.
Even if one grants that the proper usage of the word slavery is the involuntary ownership of one human by another, the initial argument remains problematic. This is because it has not been shown that self-ownership does not entail the voluntary ownership of humans by other humans or that the voluntary ownership of humans by other humans is not possible. All that has been asserted is that we should not call such ownership slavery. Yet the conclusion of the argument is problematic regardless of what collection of letters we choose to call this particular sort of ownership. For example, we may suppose to label ‘the voluntary ownership of one human by another’ ‘lavery’ such that the argument would state that ‘to transfer this right would be to transfer one’s ownership of one’s self. To be owned by another is to be a lave. Therefore self-ownership entails lavery.’ The conclusion remains identical, self-ownership entails the right to transfer one’s ownership of one’s self and so be owned as property by another.
A second and far stronger objection against the possibility of voluntary slavery is made by Rothbard In chapter 19 of ‘The Ethics of Liberty’, as part of a discussion of legitimate contracts. He writes: “Suppose that Smith makes the following agreement with the Jones Corporation: Smith, for the rest of his life, will obey all orders, under whatever conditions, that the Jones Corporation wishes to lay down. Now, in libertarian theory there is nothing to prevent Smith from making this agreement, and from serving the Jones Corporation and from obeying the latter’s orders indefinitely. The problem comes when, at some later date, Smith changes his mind and decides to leave. Shall he be held to his former voluntary promise? Our contention—and one that is fortunately upheld under present law—is that Smith’s promise was not a valid (i.e., not an enforceable) contract. There is no transfer of title in Smith’s agreement, because Smith’s control over his own body and will are inalienable. Since that control cannot be alienated, the agreement was not a valid contract, and therefore should not be enforceable. Smith’s agreement was a mere promise, which it might be held he is morally obligated to keep, but which should not be legally obligatory.”
In short, voluntary slavery cannot occur for two reasons. Firstly, an agent cannot alienate their free will and therefore their control over their own body to another agent. Secondly, given the first reason, another agent cannot control another agent’s free will and since control is a requirement for ownership, one agent cannot own another agent as property. Since the transfer of self-ownership cannot occur, voluntary slavery is not a legitimate contract but instead a promise to perform certain actions, and therefore ought not to be enforced by law.
The problem with this argument is that the debate over voluntary slavery is concerned with the transfer of the moral right to control permissible use, that is, the moral right to control which actions are or are not performed. Voluntary slavery is not concerned with the transfer of the internal psychological capacity to directly control a human body. Rothbard is right to insist that one cannot transfer one’s free will to another and one person cannot own another person’s free will. However, these two truths in no way demonstrate that one individual cannot possess the moral right to exclusively control the body of another. In Rothbard’s example the Jones corporation does not own or control Smith’s psychological capacity to control his body, rather they possess the moral right to determine which actions Smith performs and Smith does not possess the moral right to determine which actions that he himself performs. Therefore Smith may still exercise control over his body, such as moving his arm and mouth when eating, but it is the Jones corporation which possesses the right to determine what actions Smith performs such that were they to want Smith to stop eating they would have the right to psychically control his arm and mouth in order to control his behaviour and Smith would not have the right to not be externally controlled in this manner. In summary, Rothbard’s inability to separate the fact of psychological control from the right of legitimate control ensures that he is unable to separate the inalienability of free will from the alienability of a property right.
The irrelevance of the inalienability of free will to the alienability of a property right is further demonstrated when we consider the standard Anarcho-Capitalist position on the ownership of non-human animals. They generally believe that a human owner of an animal possesses rights of control over the animal and so have the right to (say) milk their cow, kill their pig and neuter their dog. They understand this fact despite it also being the case that the human is not in and cannot be in a position of direct psychological control over the animal. The fact that the animal does not itself possess the capacity of free will seems irrelevant because the issue at hand is whether or not an individual can have the right to own an existing animal while nonetheless not being in a position of direct psychological control over the animal’s body. The psychological capacities of the animal itself are not relevant to the answer of this specific question since regardless of whether or not the animal has the capacity for free will it is still the case that the owner is not in a position of direct psychological control.
This is not to deny that the fact of free will is of relevance when determining the exact rights of the animal and how they can come to be legitimately owned. For example, if one has the capacity for free will it makes proper sense to say that the animal has a right to self-determination. This is because to speak of such a right is to imply that the right can in fact be exercised and were an animal to not have free will they would not be able to exercise a right to self-determination. Moreover, an animal with such a right could only be come to be legitimately owned by another if they consented to the owning. However, both of these sorts of issues are distinct from whether or not the animal can be owned in principle by an owner who does not exercise direct psychological control over their body.
To conclude, both arguments against the possibility of voluntary slavery fail.