Here is my response that finally got approved. After rereading it, the best way for me to explain Kinsella’s point:
In a title-transfer, one person relinquishes ownership of some property so that another specific person may claim ownership. So I do consider both your example to be analogous, with the one exception being that there is an intent by the first owner in a transfer to relinquish ownership so that another specific person may claim it, whereas in abandonment, the owner relinquishes ownership so that any person may claim it.
I like Kinsella’s explanation, but I think that mine is better. I’m going to try to explain it again in a more ordered fashion.
Libertarians take the NAP to be the founding principle of libertarianism. The non-aggression principle is the golden rule, the ethic of reciprocity, applied to law. Libertarians also take the concept of homesteading to be a very important principle, but it is often taken as a premise separate from the NAP. What I am going to show is that this is not the case. I am also going to show how three other essential principles to libertarianism are derived from the ethic of reciprocity.
When the golden rule is applied to the realm of law, the result is the NAP. It is the negative form of the golden rule, “Do not aggress against others”, and another way of stating it would be, “If you respect me and my property, then I will respect you and your property”. The realm of law is tied to disputes that would otherwise turn to violence. If you and I have a dispute as to what movie to watch at the theater, this is not in the realm of law, as this would not turn to violence. But if one of us were to aggress against the other, this is in the realm of law, and now we apply the NAP to the situation. So libertarians do find the golden rule to be very important, but at the same time, libertarians are more concerned with its applications to law than to human interaction in general. But we do talk about its application to human interaction in general. People who lie and break promises soon find that other people choose not to associate with them. Shunning is a powerful tool.
So it is quite easy to see how we derive the libertarian principle of proportionality. Whether we take Rothbard’s principle of double reciprocation, “two teeth for a tooth”, or if we just stick to equal reciprocation, we can see that some sense of proportion is embedded in libertarianism. And this is precisely because of reciprocation.
The theory of estoppel can be derived from the golden rule, even though its origins are not libertarian, but then again, neither is the golden rule. Essentially, with estoppel, one cannot claim something contrary to what has been established as truth by his own actions. There is more to it, but this is the most important part to libertarianism. So, if I hit you, I would be estopped if I were to say that one ought not hit another. You would be able to hit me back. Estoppel is a legal principle that allows for reciprocation.
The libertarian theory of just property is derived from the golden rule. Property and ownership are legal terms and ideas. They require people to agree to them. So, if I agree to not violate your property, you agree to not violate mine. This applies to our homes, food, clothes, etc. It applies to first use. You make a claim to own this unowned apple tree, and I make a claim to own this unowned blueberry plant. We agree to respect our claims. This is how we also derive homesteading from the golden rule.
And we can see how the title-transfer theory of contracts is derived from the golden rule. Title is a legal term regarding the rights over property. To go with our previous example, you have title to your apple tree, and I have title to my blueberry plant. So, if we were to exchange our property, what we are really exchanging is our title to these properties, as you may not necessarily dig up your apple tree when you give it to me. You are giving me the title, the rights, to the apple tree. Rothbard insisted upon title-transfer instead of honoring contracts for the sake of honoring contracts. When you give me title to your apple tree, you are saying that you will respect the apple tree as my property. If you break from this, what you are saying is that you do not respect the apple tree as my property. Reciprocation would be that I do not respect a similar claim of yours over property.
But some libertarians, such as Rothbard and Kinsella, make an exception regarding the body. They have different reasons, but they both say that title to the body is the one exception to the rule of title-transfer theory of contracts. One way or the other, the title is inalienable, even if you want it to be. So now that we have looked at how reciprocity applies to all these other main principles of libertarianism, let’s look at how reciprocity applies to the body.
First, let us examine this statement: If I don’t respect your house, then you won’t respect mine. This is reciprocation. You make a claim to your house, and I make a claim to mine. If I violate your claim, equal reciprocation would mean that you could violate mine. But how does this apply to a voluntary slave contract? A voluntary slave contract would state something along the lines of, “I agree to be your slave, even if I disagree with this at a later date.” So what happens when I decide later that I don’t want to be a slave anymore? I cease to respect your claim to own my body. So let’s apply reciprocity: If I don’t respect your claim to own my body, then you won’t respect my claim to own yours.
Let’s look at it one more time. I give you a car. Later, I decide that I don’t like this so much, so I violate this gift and take the car back. If we follow reciprocity, we see that if I don’t respect your claim to own your car, then you won’t respect a similar claim I make. That is reciprocity. So, if I don’t respect your claim to own my body, then you won’t respect my claim to own your body. This is reciprocity. Even if we were to use Rothbard’s standard of double reciprocation, it doesn’t change the principle of the matter. To reciprocate with the claims would be that we each do not respect the other’s claim over our respective bodies.
I believe this is why it is so intuitive for most libertarians to be against “voluntary” slavery. The others want to respect contracts for the sake of contracts. But even if we were to apply reciprocity to that, we can see that in the end we must be against “voluntary” slavery, as if I don’t respect a contract stating you own me, then you won’t respect a contract stating I own you. This is reciprocal. It does not mean that any other contract need to be called into question.
And Kinsella has pointed out that honoring a “voluntary” slave contract because it is a contract is question begging - assuming it is a valid contract because it is a valid contract. We must look at why contracts are considered valid, and they are valid only in that people respect them. And why do people respect them? Because of an expectation of reciprocity. But the only reciprocation in a “voluntary” slave contract is: If I don’t respect your claim to own my body, then you won’t respect my claim to own yours.
Reciprocity is the heart of libertarianism. When we look at all of the main principles of libertarianism, we see that they all come from reciprocity. This is why “voluntary” slavery is incompatible with libertarianism. Enforcing a “voluntary” slave contract is not reciprocal. It is aggression. It violates the NAP.