This is part of a series

Apr 16, 2013


George H. Smith examines the claim that the non-aggression principle should be viewed as a defeasible presumption.

In his recent article, “Six Reasons Libertarians Should Reject the Non-Aggression Principle,” Matt Zwolinski criticizes the libertarian non-aggression principle (NAP) and calls for a “radical paradigm shift in which we put aside the idea that non-aggression is the sole, immovable center of the moral universe. Libertarianism needs it own Copernican Revolution.”

In a follow-up piece (“More on Non-Aggression”), Zwolinski explains that he doesn’t wish to jettison the NAP altogether. Rather, he objects to “the NAP as the sole and absolute criterion of libertarian justice.” He continues:


It would have been easier to comment on Zwolinski’s paper if he had confined himself specifically to Murray Rothbard’s interpretation of the NAP instead of choosing the diffuse and elusive target called what “many libertarians believe.” Many libertarians, including those who regard themselves as Rothbardians in a fundamental sense, as I do, have criticized Rothbard on a number of significant issues. (For my criticism of Rothbard’s position on war, see “Thinking About War,” published in Liberty, May 2008.)

But let’s put all this aside and deal only with Zwolinski’s objections to the non-aggression principle as he understands it. In most cases I will quote from his article directly rather than attempt to paraphrase. I do this because I don’t want to run the risk of misrepresenting Zwolinski’s objections. But the quotations will take some space, so my response will require at least two parts.

Much of this essay (and probably some of Part 2) will focus on Zwolinski’s claim that we should view the NAP as a defeasible presumption, not as an inflexible rule. My criticisms of this view will be presented a little later, but for now I want to consider his call for a “radical paradigm shift,” a “Copernican Revolution,” in how we think about the NAP.

A “paradigm shift,” as explained by Thomas Kuhn, requires a competing paradigm. So what alternative paradigm does Zwolinski have in mind? Well, he doesn’t say, but I assume it is related to treating the NAP as a defeasible presumption. But if this is the case, then we are not dealing with a radical paradigm shift at all, much less with a Copernican Revolution. The notion that liberty should be treated as a defeasible presumption was standard fare among many classical liberals throughout the eighteenth and nineteenth centuries. (I discuss this topic in considerable detail in my forthcoming book from Cambridge University Press, The System of Liberty: Themes in the History of Classical Liberalism.) Here are just two examples among many.

The presumption of liberty was defended by James Madison, who stated that he approved of some exceptions to “the rule of laissez-faire” but opposed “converting the exceptions into the rule.” As Madison saw the matter, treating liberty as a defeasible presumption provided a reasonable alternative to “the extremes of doing nothing and providing everything.”

In 1893, J. Shield Nicholson (Professor of Political Economy at the University of Edinburgh) explained how the presumption of liberty informed the thinking of those classical economists who generally favored a policy of laissez-faire.

[The classical economists] considered the presumption against State interference to be established. The rule, it is true, was never absolute and unqualified. Adam Smith himself indicated some of the most important of these exceptions, and the list has been extended by his successors.

As I said before, the presumption of liberty (which can easily be converted into the presumption of non-aggression) was a mainstay of classical liberalism, so if Zwolinski’s notion of a “radical paradigm shift” is to return to a variant of this tenet of classical liberalism, then I suggest that his Copernican Revolution is akin to shifting back to the Ptolemaic system. I say this because treating liberty as a defeasible presumption led to so many exceptions among classical liberals as to eventually render the presumption itself virtually meaningless. This erosion of the basic principle (liberty) was inevitable, since it was ultimately up to government to decide when the presumption of liberty should be overridden. Thus we had a classic case of the fox guarding the chicken coop.

I will return to this issue later. Now I wish to backtrack to the beginning of Zwolinski’s article and consider his points one by one. His objections are quite sketchy, so I don’t regard myself as obligated to write a mini-essay in response to each one. In some cases I will state my disagreement briefly and then move on. Zwolinski begins:


There are two problems here. First, the NAP usually is (and should be) expressed in terms of physical force, not violence. This is largely owing to the influence of Ayn Rand, who made the non-initiation of force (commonly abbreviated NIOF) the fundamental principle of her theory of justice. “Force,” as I shall explain in Part 2, covers a lot more ground than does “violence.”

Second, Zwolinski fails to distinguish between acts that are unjust and acts that are morally wrong. This confusion recurs throughout his paper, as when he says that, according to the NAP, “No amount of aggression, no matter how small, is morally permissible.” This conclusion does not follow from the NAP. Libertarianism is a political theory that deals with the concept of justice. It does not deal per se with establishing what is and is not “morally permissible.” That is the realm of ethics, or moral theory, which is a much broader discipline than political theory.

Libertarians frequently discuss emergency situations in which aggression (such as stealing food to survive) might be morally justifiable, even if it is unjust. If Zwolinski insists that unjust actions must also be immoral in all cases whatsoever, then he is embracing the kind of absolutism that he supposedly rejects. (I will also return to this problem in Part 2.)

Moving on:

From this principle, many libertarians believe, the rest of libertarianism can be deduced as a matter of mere logic. What is the proper libertarian stance on minimum wage laws? Aggression, and therefore wrong. What about anti-discrimination laws? Aggression, and therefore wrong. Public schools? Same answer. Public roads? Same answer. The libertarian armed with the NAP has little need for the close study of history, sociology, or empirical economics. With a little logic and a lot of faith in this basic axiom of morality, virtually any political problem can be neatly solved from the armchair.

I know of no libertarian, including Rothbard, who claims that the “rest of libertarianism” can be deduced from the NAP. The original acquisition of property titles, such as in land, is only one counterexample among many. Even if we accept a homesteading approach to land titles, which involves “mixing” one’s labor with the land, this will not tell us the specifics, such as how much labor is required and for what amount of time, what qualifies as “labor,” etc. Issues like this will depend a good deal on conventions, and they could vary from region to region. There are also problems pertaining to ownership rights in bodies of water or in the atmosphere. Moreover, the specifics of contract theory—verbal versus written contracts, specific performance, remedies for contract violations, and so forth— cannot be strictly deduced from the NAP. Nor can a theory of punishment for criminal acts. The list goes on and on. Zwolinski’s notion of a purely deductive libertarian theory is a myth. The only requirement is that subsidiary libertarian principles be consistent with the NAP, which is not to say that they can be deduced from the NAP.

Let’s consider the list that Zwolinski gave us. If his examples, such as minimum wage laws, are cases of aggression, then they are indeed unjust according to the NAP. This reasoning is the simple application of a general principle to specific cases. If all violations of the NAP are unjust, and if x, y, and z qualify as violations, then it follows that x, y, and z are unjust. But these particular applications of a general principle to concrete cases are much different than formulating subsidiary libertarian principles, many of which cannot be arrived at by deductive reasoning.

I could throw a similar list back to Zwolinski. What is his stance on murder, rape, kidnapping, child molestation, and so forth? Does he need to study “history, sociology, or empirical economics” before he can tell us whether or not these things are unjust? Let us hope not; but if he does, I would like to know what information he might glean from history or sociology or economics that would make it just (or morally permissible) for him to engage in, say, rape. But if Zwolinski doesn’t need to consult those disciplines, if he is able to deduce from a general moral principle that particular instances of rape are wrong, then may we accuse him of adopting a simplistic, absolutist approach? Would he say instead that the prohibition of rape is only a defeasible presumption? If so, then I would like to know some of the exceptions and the principle he used to identify those exceptions. Again, moving on:

On its face, the NAP’s prohibition of aggression falls nicely in line with common sense. After all, who doesn’t think it’s wrong to steal someone else’s property, to club some innocent person over the head, or to force others to labor for one’s own private benefit? And if it’s wrong for us to do these things as individuals, why would it be any less wrong for us to do it as a group—as a club, a gang, or…a state?

The latter is an excellent question. Too bad Zwolinski didn’t attempt to answer it. He continues:

But the NAP’s plausibility is superficial. It is, of course, common sense to think that aggression is a bad thing. But it is far from common sense to think that its badness is absolute, such that the wrongness of aggression always trumps any other possible consideration of justice or political morality. There is a vast difference between a strong but defeasible presumption against the justice of aggression, and an absolute, universal prohibition.

Let us now take a look at the idea of a defeasible presumption in more detail.

A defeasible presumption establishes a default position, so to speak, and it also places the burden of proof on the person who wishes to override (“defeat”) the presumption.

To say that the NAP is a defeasible presumption is to say that aggression is presumed to be unjust (or wrong, in Zwolinski’s terms) in the absence of overriding arguments to the contrary. Consider one of Zwolinski’s examples: Minimum wage laws entail using coercion, via the instrumentality of law, against innocent (nonaggressive) employers. They also prohibit voluntary agreements, as when employer and employee both agree to a lesser wage. Thus, as libertarians view the matter, minimum wage laws violate the property rights of employers and the contractual rights of employees, so they are unjust.

If Zwolinski, working from the NAP qua defeasible presumption, wishes to defeat his own presumption and maintain that a government should enact and enforce minimum wage laws, then he assumes the burden to give compelling reasons for treating this case as an exception to the general rule. There are basically two ways to do this. (If, as I discuss below, Zwolinski did not intend to defend minimum wage laws, then the following should be applied to any exceptions to the NAP that he would defend.)

First, Zwolinski could argue that minimum wage laws, though an instance of real aggression, are also an instance of good aggression. This method requires that he explain the criterion (or criteria) by which we can distinguish between good and bad aggression. And since Zwolinski can (or thinks he can) justify nonaggression as a presumption, he needs to show why his exceptions do not violate his own justification for that presumption. Thus he might say that we should presume aggression is bad except when aggression serves the common or public good, or when it maximizes social utility, or when it promotes the greatest happiness for the greatest number, etc.

Second, Zwolinski could argue that a minimum wage law is not an authentic case of aggression at all, but only appears to be such to hidebound advocates of the NAP. This was the preferred method of those classical liberals who wished to justify what seemed obvious violations of their own presumption of liberty. They frequently justified (apparent) exceptions by introducing an intermediate principle between the general presumption and a particular case. In most cases this intermediate principle was the principle of tacit consent, as manifested in a “social contract” of some sort. According to this line of reasoning, citizens have tacitly agreed to abide by majority rule when dealing with laws that do not violate inalienable rights. They have, in other words, agreed beforehand to respect certain laws regarding the disposition of property (which involve alienable rights) when enacted by a legitimate government. This element of “consent” would mean that a minimum wage law is not a real case of “aggression” at all.

There is a significant difference between these two escape routes from the strictures of the NAP. Only the first method attempts to establish exceptions to the NAP, strictly speaking, so only in that approach do we find the NAP treated as a defeasible presumption. The second route, in contrast, professes to respect the NAP unconditionally, while arguing that apparent exceptions, such as minimum wage laws, are not truly exceptions at all; rather, they have been rendered “voluntary” through the mechanism of tacit consent.

Given the manner in which Zwolinski breezes through complex problems, I cannot say which approach he wishes to defend. It is possible that he doesn’t mean to defend his own examples at all, but merely wishes to illustrate the supposedly simplistic manner in which absolutist defenders of the NAP oppose various laws. If that is the case, if Zwolinski himself opposes minimum wage laws (and possibly similar examples), then we need to know why they do not qualify as legitimate exceptions to his own presumption and, moreover, what would be needed for them to so qualify. In short, Zwolinski needs to explain the criterion of defeasibility that he uses to identify legitimate exceptions to the NAP, and how he justifies that criterion.

If, as Zwolinski suggests, he can justify a “very strong presumption against coercion,” then we will need very strong reasons for why that presumption should not apply to particular cases. Unfortunately, Zwolinski doesn’t provide so much as a hint as to how he would go about this.

It is frustrating when a philosopher engages in hit-and-run raids against a position without lingering long enough to explain what he would put in its place, but it is also hazardous to speculate on what his alternative might be. Therefore, in my next installment I will cease guessing what Zwolinski may have had in mind and proceed to examine his comments in more detail.

This is part of a series