As readers of this blog are no doubt aware, our maestro, Matt Zwolinski, has raised some hackles for his claim that the much beloved libertarian non-aggression principle is both a poor foundation for libertarianism, and, more importantly, false. I agree with pretty much everything Matt says, but I want to add some detail and support.

When I was seventeen, I read Rothbard’s For a New Liberty. It revolutionized my thinking and anchored me in the libertarian political community. As readers of FANL know, Rothbard bases the case for libertarianism on the “non-aggression axiom” which he in turn rests on principles of self-ownership, homesteading and free transfer. The central libertarian idea, Rothbard argues, is that “no man or group of men may aggress against the person or property of anyone else.”

Despite my previous status as a card-carrying Rothbardian, I abandoned the NAP. I abandoned it in part because I came to believe that the NAP is not a foundational principle of justice. To see why one might agree with me, let’s consider why one should accept any normative principle as foundational.

A normative principle is foundational just when it provides an ultimate or non-derivative explanation of the normative force of a suitably broad range of considered normative judgments. A foundational principle should therefore have at least two theoretical virtues: it should be (i) comprehensive and (ii) ultimate or basic. A principle should be comprehensive in virtue of explaining the force of a wide range of our moral and political intuitive judgments. A principle is ultimate or basic if it’s normative force is non-derivative. In other words, its normative force is not derived from some more basic principle but is compelling in itself.

On this score, consider consequentialism, which loosely holds that all moral facts are made true solely by facts about consequences. The principle is simple and elegant, and also plausibly basic. Caring about consequences just seems morally relevant. However, the common worry about consequentialism is that it fails to ratify many of our core moral judgments. This is why historically consequentialists have had moral views at significant variance with the societies they lived in (from Bentham to Peter Singer). Some consider this radical stance a virtue, but accepting a moral principle with radically revisionary implications for morality has a theoretical cost because it is not suitably comprehensive.

To have good reason to endorse the NAP, we need reason to think that its explanation of our intuitions about justice is comprehensive and ultimate or basic, that is, compelling in itself. Matt has argued that the NAP lacks comprehensiveness: it cannot explain a wide range of our intuitions about justice. But we should also reject the NAP as a foundational principle because it lacks ultimacy.

Here’s why. Even Rothbard acknowledges that the real foundations of libertarianism are the twin ideas of self-ownership and initial acquisition. Rothbard thinks (wrongly) once you give him these two ideas, the rest of libertarianism follows. It doesn’t, simply because the principle of free exchange and contract doesn’t follow from the simpler, intuitive ideas of self-ownership and homesteading he relies on.

In the end, libertarianism actually relies on four principles (as Nozick saw): a principle of bodily ownership, a principle of acquisition of external property, a principle of transfer of external property (and perhaps some parts of the body) and a principle of rectification for when the first three principles are violated. Let’s call these the principles of self-ownership, acquisition, transfer and rectification.

Already we can see that the NAP is not a foundational principle of justice. At best, it is a useful rule of thumb for generating specific libertarian commitments for those who already buy the four basic libertarian principles. So the NAP just isn’t ultimate. And if Matt is right, it’s not comprehensive either.

The natural reply to these considerations is to inquire about alternatives. How are we to justify libertarianism if not by appeal to the NAP? Well, plenty of libertarians have answered this question in different ways: there are eudaemonist justifications (Long, Den Uyl, Rasmussen, Rand), natural law justifications (Chartier), other natural rights justifications (Mack), Hobbesian contractarian justifications (Narveson, Gauthier), Kantian contractualist justifications (Gaus and, I think, Hayek), rule-utilitarian justifications (most economist libertarians, Friedman, Mises), institutional-consequentialist justifications (Schmidtz), and Rossian pluralist justifications (I think MZ counts here, and maybe Huemer). In other words, there are probably decent arguments for libertarianism on just about any moral foundation.

For my part, I go for a Kantian contractualist foundation suitably chastened by political liberal concerns about reasonable pluralism. But if you read the blog, you know that already.