A Closer Look at the Non-Aggression Principle

The non-aggression principle (NAP) or axiom is considered foundational to libertarianism. In For a New Liberty: The Libertarian Manifesto, Murray Rothbard says:

The libertarian creed rests upon one central axiom: that no man or group of men may aggress against the person or property of anyone else. This may be called the “nonaggression axiom.” “Aggression” is defined as the initiation of the use or threat of physical violence against the person or property of anyone else. Aggression is therefore synonymous with invasion.

Many terms and concepts in common use suffer from ambiguity or contradictions and the NAP is no different. I hope to show that great caution is needed to avoid circular reasoning and that the NAP’s strength is more narrow than commonly assumed.

Appeals to the NAP are always appeals to rights or entitlements because rights must first be defined before we can determine if a right is being violated or protected. This is why any discussion you’ve seen involving the NAP immediately jumps to justifications for property or other rights.

A theory of entitlement is sufficient on its own. The purpose of defining rights is to have a guide for when force is justified, so adding the NAP amounts to “force is not justified in those cases where force is not justified.” Julian Sanchez goes through this in greater detail in The Non‐​Aggression Principle Can’t Be Salvaged—And Isn’t Even A Principle:

But all the real action is in the definition of rights; invoking the NAP adds nothing. It is tantamount to saying “only enforce rights that are really rights.” To establish your right over (say) your car just is to establish that I ought not to take or use it without your permission (perhaps barring extraordinary circumstances, the parameters of which will tend to be implicit in the argument establishing the right). It is neither necessary nor illuminating to add the additional premises that taking what you have a right to counts as “aggression,” and that one ought not to aggress.

It is futile arguing the NAP if the other party has a different theory of entitlement since the discussion lacks a shared understanding of rights and thus what is meant by aggression. Consider the following from Matt Bruenig in Non-aggression never does any argumentative work at any time:

Let’s use another example. Suppose I go to tax you. My claim is simple. You are not, under my theory of distributive justice, entitled to the amount I am taxing you. It does not belong to you. It belongs to the retired person it is headed to. You then resist. So I use force where necessary to extract the tax.

Now there are two moves you can make here, one makes sense and the other doesn’t. The one that makes sense is to say: this is an unjust tax because the amount being taxed belongs to me, and I am entitled to it. The one that doesn’t make sense and does no argumentative work whatsoever is to say: this is aggression.

The reason it makes no sense is because it does what philosophers call begging the question. Why is taxing you aggression rather than defense? Well it’s aggression because you are entitled to what is being taxed from you (you claim). Fine, I hear that you believe it belongs to you. But I don’t believe it belongs to you. So really when you say it is aggression, you are just assuming as an unstated premise exactly what we are disagreeing about: whether the thing actually belongs to you or not. If I am right about the thing not belonging to you, it’s not aggression. If you are right about it belonging to you, it is.

These are certainly devastating critiques, but we aren’t finished just yet because David Gordon is here to save the day. In Is the NAP a Useless Tautology?, he argues that adherence to the NAP prevents force in the absence of an identifiable claim:

Here Sanchez has focused on the wrong word. He says, in effect, “Of course you should only enforce an enforceable claim. What else do you propose to enforce — a non-enforceable claim?” He is certainly correct that you shouldn’t enforce a non-enforceable claim, but he has missed something. He has not paid enough attention to “claim.” If you have a moral claim, then something is owed to you. Moral claims are personal. But some moral theories don’t tie the use of force to claims.

As an example, someone might favor transfers of wealth from billionaires to the poor on the ground that this will increase utility. The person might further hold that force can properly be used to do this. In taking this view, the person need not have rights in mind at all. The argument isn’t that the poor have a right to the transfers of wealth, so that if the transfers aren’t made, the poor have been deprived of what is morally owed to them. Rather, the theory holds that transferring wealth in this circumstance is a good thing to do and that’s all you need to justify using force.

In brief, there are non-rights based moral theories. The NAP, by tying the use of force to rights-violations, rules out using force to achieve moral goals not founded on persons’ claims. It is thus not a tautology.

In other words, while others may attempt to justify the use of force on utilitarian or some other non-rights grounds, the NAP informs libertarians that any use of force should be backed up with a theory of entitlement.

The same logic applies to moral theories that do include rights considerations but sometimes override them with justifications for the use of force not based in rights. David continues:

Sanchez might answer that the NAP adds nothing to “People have rights” or a list of these rights. These already exclude moral theories not based on rights. This answer is also not correct. Someone who favored the wealth transfer might say that enough of an increase in utility overrides the billionaires’ property rights; the billionaires can be forced to transfer their wealth if they don’t want to do it. Again, this isn’t to say that the poor have a right to the transfer. Some moral theories include both rights and other considerations as well that justify using force. The NAP blocks using force that doesn’t respond to a rights violation, so it does add to “People have rights.”

Sanchez is correct that the NAP doesn’t by itself block a theory that includes non-libertarian rights, but this doesn’t make it useless for libertarians. The NAP doesn’t do everything, but it does do some things.

A restatement of the NAP can clarify our thinking here. Something like “All justifications for the use of force should derive from some theory of entitlement.” From here we can more easily see that an argument based primarily on, for example, utility maximization cannot be compatible with NAP libertarianism.

The NAP should be used with caution to avoid tautological reasoning or talking past your discussion partner. But the NAP does have some benefit for those who choose to adopt it, namely, as a reminder that the use of force should be preceded by reflection on the rights of those involved and ruling out ethical theories for the justifications of force where rights are not the centerpiece.