Walter Block* defines the non-aggression axiom (sometimes called the non-aggression principle, or NAP for short) as follows:

It states, simply, that it shall be legal for anyone to do anything he wants, provided only that he not initiate (or threaten) violence against the person or legitimately owned property of another.

Suppose for the sake of argument that the NAP is true. Suppose it’s not just a prima facie obligation, either. Instead, suppose that it is an absolute principle–no contrary consideration can ever outweigh it. In a previous post, I pointed out that even if so, this doesn’t give libertarians a knock-down argument for libertarianism.

The reason is that socialists, statists, and others can, and some do, accept the NAP. The difference between libertarians and non-libertarians is not about whether aggression is permissible. Instead, it’s about what counts as aggression, or about just who has a right to what.

A statist might say the following, “I believe in the NAP. That’s why it’s imperative that you pay your taxes to your legitimate government. After all, since the government and those taxes are legitimate, the government has a right to that money. It’s not yours. If you kept it, you would be stealing it from its rightful owner, the government.”

A socialist might say the following, “I believe in the NAP. That’s why it’s imperative that capitalist factory-owners and land-owners relinquish control to the proper owners of capital, all the people as a whole. The people have a right to those goods. Those goods do not belong to the capitalists. If the capitalists keep the factories and land to themselves, they steal from the rightful owners, which are the people.”

This is why the NAP is itself impotent in an argument. It does no work. Everyone can just agree to the NAP without that resolving anything. What the socialist, the statist, and the libertarian dispute is not necessarily the NAP, but rather who owns what and why they own it.

Consider Tom Christiano, a left-leaning democratic theorist at the University of Arizona. Christiano is one of the best political philosophers alive today. His response to the NAP argument could be, “Sure, it’s wrong to violate people’s rights by taking away their stuff, but that’s not what I’m advocating. For, as I explain here, while people have private property rights, the government also has rights of control over property within certain limits. I’m not saying everything belongs to the government, of course. But some governments do have rightful claims to tax their citizens, and the money they tax actually belongs to the government, not to those citizens.”

Now, how could Bl0ck argue against Christiano? Two ways:

1. Block could produce a good argument for Block’s favored understanding of property rights. Here, the NAP would play no role in justifying those rights, because the NAP instead references those rights. What the NAP requires depends on what our rights are, and that’s determined independently.
2. Block could poke a hole in Christiano’s argument, showing that is has a serious flaw.

But Block can’t argue against Christiano by invoking the NAP. Christiano can just say he accepts the NAP.

*Note: I’m not criticizing Block here. I’m not familiar with his stuff other than his Defending the Undefendable book, so I don’t know if he commits the error that I’m discussing here.