Free Thoughts Blog

The socialist calculation debate is an important episode in the history of economic thought in part because it revealed some of the previously underappreciated things that markets accomplish. It did so by supposing the existence of a socialist planning agency that would have to do all of those things instead - a thing that many socialists of course wanted, but that supporters of the free market have also found very useful to examine. It turned out that the planning agency would face a large number of previously unanticipated problems. Many of them now appear insoluble.

Not that we haven’t tried. On the contrary, lots of work has been done here. That work illuminates what markets actually accomplish (not always what we thought they did!), what economic science can know about them (not as much as we’d like!), and what institutions, if any, might ever be able to improve on them.[1] There are many facets to the socialist calculation debate, and in what follows I’ll talk about only some of the more relevant ones.

One problem in talking about this fascinating episode in the history of economic thought is that each of its lines of argument is often conflated with the others, and, at times, an author raising objections to the prospect of socialist calculation will veer from one problem to another with little in the way of transition. I’ve tried hard to sort out the threads as I see them, but it’s very possible that someone more well-read in Austrian economics will come along and disagree.[2]

Anyway, let’s begin looking at objections.

I. The Math Is Too Hard.

This is by far the weakest objection to the prospect of socialist calculation. It’s also one that I still seem to find in all kinds of places, and still offered as if it mattered. It doesn’t, and it’s not a terribly important objection anymore, but it’s necessary to go through it to get to the interesting stuff.

By the early 20th century, economists had shown that in theory, a centrally directed socialist allocation of resources could match that of a market economy that was in a Walrasian general equilibrium.

What’s a Walrasian general equilibrium? The economist Léon Walras had earlier shown mathematically that, under certain not obviously problematic assumptions it was possible for the markets in many different goods to clear simultaneously – that is, a multi-good market could theoretically adjust all of its prices so that supply and demand were in balance for all goods at the same time. Producers could theoretically make the exact amounts needed to fill consumer demand, and consumers who were willing to pay the market price could always get what they wanted. Most importantly, Walras showed that nothing about the simultaneous existence of many different goods in his model would get the way of the process, and the existence money wouldn’t either.[3]

General equilibrium has obvious appeal, and yet real-world economies never seem to reach it. Walras himself emphasized that markets only approximated his theoretical equilibrium through a process he called tâtonnement–literally, “groping.” And they were therefore not terribly efficient when compared to the mathematical ideal. Which I think is true.

Scientific socialists, in part inspired by Enrico Barone, proposed to do better.[4] Solving the right system of equations would in theory give planners the optimal allocations of all capital and consumption goods, allowing them to reach Walrasian equilibrium directly, even as markets could only grope about in the dark.

In the early twentieth century, theoretical economists – even folks like Lionel Robbins and F.A. Hayek – conceded that all of the above was true. But, they said in part, the math was just too hard. It’ll take forever to solve all those equations.[5]

But forever is a very long time, and today we have computers that can most certainly crack problems like this one. Even, as some have claimed, for an economy with millions of goods.

In 1993, Allin Cottrell and W. Paul Cockshott examined the calculations needed to very closely approximate market-clearing prices for all goods in the Soviet economy circa 1983. For this economy of around 10 million goods, and using only a commercially available supercomputer of mid–1980s vintage, they determined that market-clearing prices, denominated in hours of unskilled labor, could be roughly arrived at in just 17 minutes.

That’s a pretty impressive result. So impressive, in fact, that one gets the feeling that something else must almost certainly be going on here.

And indeed, something else is going on here, but what it is will have to wait for the next post in the series.

In his post on pollution and the non-aggression principle, Matt Zwolinski begins by telling us that “Libertarians generally believe that aggression against innocent persons is morally wrong, and that the only just use of violence is to prevent aggression by others.” Somewhat less imprecisely, we might say that the only just use of coercion (using force and the threat of force against people) is to prevent or redress aggression.

He then says, “In this respect, at least, the liberal egalitarian philosopher John Rawls was on precisely the same page as his libertarian colleague, Robert Nozick” and quotes Rawls on “freedom” purportedly to that effect. However, Rawls has an understanding of “freedom” that is inherently political and which sanctions much that libertarians would rightly see as itself involving aggression. Consequently, Rawls and Nozick are certainly not “on precisely the same page”.

We are soon asked, “Suppose I aggress against you not by beating you over the head with a club, but by blowing tobacco smoke into your face? The smoke-blowing, just like the clubbing, is a physical invasion of your body. And it is a harmful invasion.” And here we should note that the physical harm itself is irrelevant to liberty. What matters is that the victim disvalues the invasion for whatever reason. If an aggression were to improve the victim’s health, then it would still flout his liberty.

After such considerations, Zwolinski concludes that “The consistent application of Rothbard’s absolutist principle of non-aggression thus seems to require a prohibition on all forms of non-consensual pollution.” And in its absolutist form I agree. However, this overlooks something crucially important: it cuts both ways. The enforcement of the prohibition would itself aggress against the people whose activities would produce the pollution (e.g., having fires for needed warmth and cooking). So such prohibitions cannot be allowed either. We have reached not one but two unacceptable conclusions and, more to the point, they amount to an inconsistency in the “absolutist” version of the theory. Hence that form of the theory is a priori refuted. (I know that Rothbardians try to introduce various points to solve such problems, but they look ad hoc and invalid to me.)

There are two main problems with the absolutist theory that lead to this result. First, while liberty itself can be interpreted as the absence of aggression, the libertarian policy must be to minimize aggression when there is such a clash as that described. Thus some sort of compromise is required, maybe with some damages being paid in one or the other direction. Second, “aggression” understood in terms of violating property rights is only a rule of thumb. “Aggression” can be more abstractly and accurately theorized as proactively imposing costs (such as both pollution and pollution prohibitions) on other people. This pre-propertarian theory is required for consistently solving such property problems, paradoxes, and inconsistencies whenever they occur.

This alternative approach should become clearer and more cogent as I reply to Zwolinski’s final essay, in which he attempts to refute the “non-aggression principle” beyond any salvation.

Just to clear up any misconceptions, I think the minimum wage is an unjust and inhumane public policy. It is morally wrong. I also believe—I hope less controversially—that rape is a serious moral wrong. And no, George, I didn’t need to study history, sociology, or empirical economics to come to that conclusion.

I suppose George Smith thinks he has snared me in some sort of philosophical trap by forcing me to admit this. After all, in my original essay on the libertarian Non-Aggression Principle (NAP), I criticized devotees of the NAP for the casually a priori approach they often take to issues like the legitimacy of public roads, public schools, and the minimum wage. But—A-ha!—if I don’t think that careful empirical study is necessary to determine the injustice of rape and child molestation, then how can I simultaneously hold that it is necessary in order to determine the injustice of the minimum wage? Gotcha!

Well, maybe it doesn’t sound quite so much like a gotcha when I put it that way. Is it really so absurd to believe that the immorality of rape is considerably easier to discern than the immorality of the minimum wage? That the latter might require a more careful study of a wider array of empirical evidence than the former? I suppose it doesn’t seem that way to me. Some acts wear their immorality on their sleeve—it is part of “what is seen,” to borrow Bastiat’s famous distinction. With others, and perhaps the minimum wage is one of them, most of the wrongness derives from facts that are “unseen,” and require a bit of careful digging to unearth. Is there really an inconsistency here?

Of course, if you think as I do that coercion is bad, then you’ll think that minimum wage laws are prima facie objectionable even before engaging in this digging. But notice that even in the case of rape, we wouldn’t want to end our analysis here. Rape is coercive, yes. And it involves a violation of one’s property in one’s body. But if this is all we understood about rape, then we wouldn’t have come anywhere close to understanding the full weight or significance of its injustice. We wouldn’t understand the devastating psychological effect that rape can have on a woman. We wouldn’t understand that women are often blamed for their own rape, or the ways our entrenched institutions protect rapists while shaming and silencing their victims. We wouldn’t understand, in other words, why a lot of people think rape is an especially serious injustice, or one that calls for more attention and more action to effectively combat.

Rape is aggressive and a violation of property rights, just like stealing someone’s car radio or imposing a minimum wage law on them. But rape is not just like a minimum wage law. And that is because aggression and property rights are, by themselves, not the only categories relevant to moral or juridical evaluation.

This is a rather obvious point, as far as moral philosophy goes. But it does seem to pose a challenge to those who believe that all the thorny questions of justice can be resolved by the application of a neat and tidy principle like the NAP. If not all aggression is on a par—if some, like rape, is very seriously wrong, while some, like shining a flashlight at your house, is not wrong at all—then why should we believe that the non-aggressiveness or aggressiveness of conduct is anything like a sufficient indicator of its justice or injustice? And why should we believe that aggression (no matter how small) must never be permitted in order to produce any kind of social or individual benefit (no matter how large)?

Smith raises a number of other points in his essay, most of which I won’t be able to address here. Which is just as well, I suppose, since he hasn’t yet managed to develop many of those points himself. He stresses (contra Rothbard) that the NAP is about “force,” not “violence,” but doesn’t bother to explain what he takes the difference between those two concepts to be. He asserts that the NAP is about justice, not about moral permissibility, but again he leaves the difference almost entirely unexplained. Since these distinctions appear to play an important role in Smith’s argument, I assume that he will explain them at some point in his series. But until he does, there is little I can do to respond to them.

Smith concludes his essay by accusing me, somewhat uncharitably, of having engaged in a “hit-and-run” against the NAP. I’m not sure what he was expecting from a 1,200 word blog post. Apparently, criticizing the NAP on a number of grounds isn’t enough—I should have developed and articulated my own alternative theory of libertarianism too. Well, I’m happy to do that, and to discuss in more detail the various topics I raised in my initial post. There is certainly more to say about each of them. So I must object to Smith’s characterization. It’s only a hit-and-run if you hit and then run. And I’m not going anywhere.

There has been much buzz lately in libertarian Internet circles concerning the Non-Aggression Principle (NAP), a favorite ethical maxim adopted by many libertarians in defense of anarcho-capitalism. This increased attention to the NAP is due in large part to Matt Zwolinski’s excellent article articulating many of its counterintuitive implications. Zwolinski recommends that instead of radically editing the principle as stated – that is, instead of adding epicycles to our original understanding of the orbital paths of celestial bodies – libertarians ought to undergo a “Copernican Revolution” by developing a new ethical system to justify our preferred socio-political order. Like any good controversy, there has been much response, most notably by Jason Kuznicki in his equally-excellent essay “Non-Aggression and Billiards.” In this essay I examine Kuznicki’s defense of the NAP, not necessarily as an absolute and inviolable axiom, but at the very least as a strong though rebuttable presumption.

We are all taught that certain things are true when in actuality they are false. We are taught, for instance, that there are three inviolable laws of motion governing all moving bodies in our universe, when in reality things work a bit differently when we start dealing with very small particles. We are also fed exaltations concerning the immutable axioms of Euclidean geometry when such an axiomatic system remains contingent upon a series of assumptions that may or may not hold true. Even so, these kind-of-true-but-strictly-speaking-false principles of physics and mathematics are very useful to us: they can allow us to understand how billiard balls interact with one another, or perhaps they help us find out how much manure we need to help fertilize a 16 foot by 24 foot field.  The NAP, so Kuznicki argues, is of similar value: it gives us a good starting point to help determine when actions are morally right and morally wrong, though some refinement, or “engineering,” might be required for more advanced situations.

But many times Newtonian mechanics and Euclidean geometry are insufficient. Surely the rocket scientist and quantum cryptologist need to go beyond high school mathematics and physics classes in order to do their jobs properly. This, of course, does not change the fact that most people need only an elementary understanding of physics and mathematics to get through their day-to-day lives. But in comparing the NAP to something like Newtonian mechanics and Euclidean geometry, we need to see if the analogy carries over to this corollary: do practical agents, trying to navigate through life, require only the NAP to help guide most of their decisions, or do they need a more robust version of the NAP – or perhaps a new moral system altogether – in order to navigate life’s imbroglios? As practical agents, are we high school students or rocket scientists? 

I contend that we are rocket scientists. We are rockets scientists not because life is that hard a thing to navigate through (though it certainly has its harsh contentions), but rather because the high school math many libertarians want us to adopt – the NAP – is so insufficient as a moral theory that it cannot stand up to the basic experiences we all, as practical agents, face. For example, most of us, it seems reasonable to suggest, will end up having and raising kids. Will the NAP (Newtonian physics) tell us how to raise them right? As Zwolinski points out, it will not only not tell us how to raise our kids correctly, it will, in actuality, approbate actions that any sane person would think constitutes morally impermissible methods of child rearing. Thus, quantum mechanics is required. Many of us also frequently engage in behavior that yields some sort of environmental pollution. Will the NAP (Euclidean geometry) gives us the right answer as to what we ought to do? Again, no. It will tell us that we cannot, as Zwolinski once again points out, drive an automobile or light a campfire, conclusions that are surely absurd. Thus, non-Euclidean geometry is required. Several people are confronted every day with the chance to commit some kind of fraud to make a quick buck or reap some benefit. Will the NAP tell these individuals how they ought to act? As Zwolinski shows, it will not. Our high school physics and mathematics has failed; we need a more sophisticated theory.

Since the adoption of the NAP results in rocket scientists trying to make their way with Newtonian mechanics, we need to beef up the NAP, rendering it capable of handling the sorts of problems we as rocket-scientist-like practical agents face. In editing the NAP, there seems to me to be two paths we can take. First, we can radically alter or add to our definition of “aggression,” in hopes of reproaching the sorts of actions our original NAP failed to delimit as off-limits. Kuznicki offers an attempt at doing this in hopes of rendering fraud impermissible; namely, he advocates we classify as morally impermissible actions that are “impediments to reflective self-rule” to go along with our ban on brute physical aggression. This may work, but it is certainly not enough. What do we add to physical aggression and impediments to self-rule if we are to outlaw a parent starving their child? What do we add to allow for reasonable amounts but not too much pollution? Moreover, we also run the risk of our amendments yielding results we find unacceptable. Would my neighbor playing loud heavy metal music several hours throughout the day impede my ability to reflectively self-rule? Maybe, if it sufficiently hindered my concentration. Yet most libertarians would find it acceptable to do something on one’s property as benign as playing loud music. So now we need to further edit what is meant by “reflective self-rule” to account for this result. Epicycles upon epicycles.

The second way we can strengthen the NAP proceeds as follows: we can keep our original understanding of what constitutes aggression, but then add a list of exemptions we consider to be legitimate instances of when the NAP may be transgressed. We then get something like this: it is morally obligatory to follow the dictates of the NAP except in cases x­₁, x_2­, x₃,…, x_n, in which case it is morally permissible (or perhaps obligatory) to disobey the dictates of the NAP_­. The problem, though, remains that variable n can be a high – indeed very high – number, to the point at which listing all exemptions becomes difficult, if not impossible. In fact, there is probably a case to be made that, given the tremendously narrow scope of the NAP and the ingenious ability of philosophers to dream up counterfactuals, the list of exemptions might be un-codifiable, presenting a problem for this approach to amending the NAP. Instead, it might be argued that rather than listing each and every exemption to the principle, we might simply develop a secondary rule determining when some situation constitutes a legitimate instance of when the NAP may be permissibly violated. But this project also seems rather hopeless, for any rule that concretely adjudicates exemptions from non-exemptions will have to contain excruciating detail – perhaps an un-enumerable amount of detail (we could not, for example, simply say that situation s constitutes an instance permitting exemption from the dictates of the NAP just in case situation s yields a severe reduction in an agent’s autonomy, because it is not clear what constitutes a “severe reduction in an agent’s autonomy”). Once again, epicycles upon epicycles.

It is not the case that every ethical system yielding implausible implications through counterfactual analysis must be abandoned for another ethical system. It might be that an ethical theory is polished to the point that it can be revised to such a miniscule extent that it remains worth holding on to – after all, one or two epicycles does not grossly detract from the elegance of an otherwise perfectly elliptical orbital path. But there comes a point when the amount of revision borders on the absurd – after we have drawn the fifteenth, sixteenth, seventeenth epicycle. At this point, it makes sense to start anew in hopes of developing a better theory that does not require such extensive revision, allowing for maintained elegance. I think the NAP is in this latter category. As such, it is high time we, as libertarians, do as Zwolinski bids by undergoing our own Copernican Revolution in search of a better moral and political philosophy.

During his recent diatribe against libertarians Bill Maher said, “Libertarians also hate Medicare and Social Security and there are problems with those programs but here’s the thing: It beats stepping over lepers and watching human skeletons shit in the river and I also like not seeing those things.”

Libertarians hear this sort of thing a lot. “You don’t think there should be limits on campaign spending? Then you must want corporations to buy elections!” Or, “You’re opposed to public schooling? What, you think all our children should just stay ignorant?”

We call this a false dilemma, a well-known logical fallacy. A person commits it when he limits the available choices in an argument too much. You can pick between A or B, he says, when in fact there’s an option C (and D, E, and F), as well. For Maher, either we keep Medicare and Society Security or we allow horrific poverty.

The false dilemma’s a logical fallacy for good reason and so by itself is never a good argument against, well, anything. But that doesn’t mean we should just ignore it. Instead, once we’ve noticed how many people employ false dilemmas against libertarian proposals, we should take a moment to ask why.

I submit that the false dilemma’s prevalence results in part from the way many libertarians talk about, and argue for, their political views.

If you have no reason to think options exist beyond just A and B, then if you hear someone arguing strongly against A, it’s not stupid to assume he’s either in favor of B or at least prefers B to A. So if you aren’t aware of any ways to prevent destitution besides Social Security, and you hear a libertarian arguing strongly against the morality of Society Security, then it’s rather likely you’ll conclude that he either wants destitution for the poor or at least would rather see the poor destitute than suffer the moral harm of Social Security.

Libertarians bear some of the blame for this. Quite often when choosing our rhetoric, we have a tendency to focus on “not A” instead of saying, “B’s not good either, so let’s instead do C.” For example, folks on the left are less likely to attack us with false dilemmas if we focus not so exclusively on the rights violations inherent in paying for Social Security, but instead point out that Social Security doesn’t work all that well or efficiently if the goal is to prevent destitution, and then offer better alternatives.

This “not A” tendency could result from the simple fact that offering alternatives means having persuasive alternatives in mind. And while they’re myriad, not all of us have the time or inclination to learn them. Call it a kind of rational ignorance in political debate. Far easier to just apply a single principle, a “universal acid” as Daniel Dennett calls it.

But we’re often also motivated by a desire to maintain our principles. Principles are good, of course. That libertarians say we value freedom and mean it is a crucial difference between us and conservatives and progressives. On the other hand, we need to recognize that non-libertarians don’t accept our core principles. If they did, they wouldn’t be non-libertarians. So if our goal is not just to be right, but to be persuasive, then starting with common ground can be rather more effective. Yes, we take a principled stand against the state coercion behind Social Security, but we also don’t want people to suffer from rampant poverty. In fact, much of what’s appealing about libertarianism is that it’s a genuine path to both: we can be free and prosperous. We shouldn’t water down our libertarianism but we should pay attention to when leading with the argument from prosperity—and using it as a way to then persuade on the issue of freedom—can be more effective than making only the argument from freedom.

Bill Maher’s fulmination just shows that the way we express our ideas is often as important for their persuasiveness as the ideas themselves.

Jason Kuznicki makes a game attempt to salvage the “Non-Aggression Principle” from Matt Zwolinski’s six-pronged assault, essentially arguing that the NAP is something like Euclidian geometry or high school physics—a simplified model that may be, strictly speaking, false in its pure form, but serves as a good enough rough rule for most circumstances. And this may seem promising if we think about other moral principles and rules about which something similar can be said. Parents typically teach their children that one ought always to tell the truth, but most will acknowledge that there are many exceptions—cases where some degree of deviation from the general rule is either permissible (to spare someone’s feelings or protect a confidence, if the subject is trivial) or even obligatory (the canonical “murderer at the door” asking where his prospective victim may be found). I doubt this will work for the NAP, however, for several reasons.

First, the viability of a principle has to be judged in the context of what role it is meant to be playing in your ethical thinking. If the NAP is understood as akin to “tell the truth”—one among many rules of thumb that establish rebuttable presumptions for guiding your daily conduct—then it is perfectly servicable. May I respond to an insulting remark by throwing a punch? I may not. But that is not really how libertarians usually want to use the NAP: Rather, it is meant to serve as a kind of master principle from which other more concrete rules may be derived, and against which competing forms of social order may be evaluated. And for that purpose it is not particularly useful. When we are not looking for rough guides to our day-to-day conduct, but engaged in the rather more leisurely activity of theory-building, there is less practical reason to rely on simplified models because “the math is easier,” and more to the point, we are most likely to be wrestling with precisely the kind of hard cases that arguably constitute exceptions to the rough rule, or deciding between variant forms of the very concepts on which the NAP relies.

If the NAP were truly a universal, exceptionless master principle—if the apparent counterexamples were either bullets we could bite or cases where the principle would yield the right answer after all once properly understood—then we could employ it directly even at the highest theoretical level. But if, as Jason seems to concede, we are allowing that the exceptions are really exceptions, then we are implicitly relying on some other higher-level principles—respect for autonomy or hedonic utility or Kantian universalization or contractualist agreement—to limn the boundaries. But at the theory building level, the appropriate thing to do is to refer directly to those deeper principles. To extend the initial metaphor, it is precisely when you are trying to do fundamental physics that you end up needing to step back from the approximate truths of classical mechanics. The NAP is no help deciding the questions you’re attempting to answer at this level, because as Zwolinski notes, it’s parasitic on theories of property and coercion that reside at this same level of abstraction. You can’t resolve a philosophical debate between a classical liberal and a socialist by appealing to the NAP, because each can claim their view is consistent with that principle given their theories of property: The state is not “aggressing” on an individual “property owner” if in fact The People ultimately own (or have some kind of share right in) all property, given the normatively loaded way “aggression” is used here. The appeal of the NAP lies in its apparent simplicity and intuitive plausibility (tautologies tend to be intuitively plausible), but it’s typically deployed in a way that amounts to a kind of shell game: I argue that socialism must be rejected on the grounds that it violates this one simple moral principle, and hope my interlocutor doesn’t notice that I’ve essentially begged the question by baking a theory of strong property rights incompatible with socialism into my conception of “aggression,” when of course libertarian property rights are ultimately backed by the threat of (individual or state) violence as well.   

This gets us to the deeper problem with the Non-Aggression Principle: It is not really a principle at all, but a tautology gesturing in the direction of a theory. Suppose I tell you that I have, at long last, discovered the simple principle from which all morality derives. Assuming you suppress your initial skepticism about this bold claim, you are likely to be disappointed if I then reveal that my principle is something like “One ought not to commit wrong actions,” or “Never violate the rights of others.” The latter is not completely content free—it specifies that it is the moral claims of individuals that matter, rather than compliance with some natural or divine law unmoored from human consequences—but neither principle really gives us the concrete guidance we had expected, even at a highly abstract level: These are formaltruths given the meaning of the normative terms “right,” “wrong,” and “ought,” not substantive guides to which actions or social orders satisfy these conditions. This is slightly less obvious in the case of the NAP because the partly-descriptive term “aggression” seems to add a substantive component. Yet this amounts to little more than the recognition that we are creatures made of matter whose moral entitlements are ultimately guaranteed or made effective by the application or (more often) implicit background threat of physical force in the last resort. A “right” is a claim that you are justified in ultimately resorting to (direct or indirect) force to make effective; whether or not a particular act counts as “aggression” or “initiation” of force depends on whether the right enforced is a genuine one. 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.

Now, it is surely true, as Jason suggests, that any simple principle is going to be highly incomplete and tied to a larger theoretical apparatus. The utilitarian principle of “the greatest good for the greatest number” does not tell us whether to maximize aggregate or average utility, or whether to concieve of utility in purely hedonic and subjective terms, as a measure of preference satisfaction, or something else. The Rawlsian Difference Principle, which stipulates that social inequalities are justified only to the extent they benefit the worst off group in society, does not in itself tell us how to understand “worst off”: For Rawls, it is determined by a laundry list of “primary goods,” but one could just as easily apply a variant difference principle that used hedonic utility instead. The Millian Harm Principle—individuals may be restrained only to prevent harms to others, not to themselves—notoriously runs into a thicket when we try to specify precisely what counts as a “harm.” It is no objection to a principle that it depends on theory. But it is an objection if the principle is being made to do load-bearing work—treated as a fundamental “axiom” rather than a presumptive rule derived from higher-order principles—that conceals those dependencies. The utilitarian principle—though “gappy” and therefore susceptible to a wide array of variant interpretations—really is “axiomatic” in some sense: The basic idea that one ought to weigh the interests of all equally—and then act in the way that (or follow the rule that) generates the greatest net of benefits minus burdens—really is fundamental in utilitarian theory. It is not quite that there is nothing further to say about why it might be plausible or not, but we are pretty close to the core intuition at the heart of any moral theory that one ultimately either shares or doesn’t. The Harms Principle and Difference Principle, by contrast, are transparently derivative rules, the upshot or result of a lengthy preceding argument in light of which they are to be interpreted, fleshed out, and applied to particular circumstances.

The NAP as deployed in much libertarian rhetoric tends to trade on an ambiguity between these two types: It often masquerades as the former, even though it only really has content if understood as the latter. We then often end up being misled into thinking we can defend a particular form of sociopolitical order just by appealing to the simple and intuitively plausible NAP, without noticing that the highly intuitive formal NAP only gets substantive content by choosing a specific cluster of contestable conceptions of “aggression,” “property,” “coercion,” “consent,” and so on. Yet the choice between these conceptions ultimately just is the choice between competing sociopolitical orders—so arguments of this form are circular.

None of this is to deny that the NAP may be a perfectly servicable way to sum up what libertarianism is all about to the fellow on the next stool at the bar who’s never heard of it. But if we are doing political philosophy, we are probably better off leaving it behind: It is a principle that does no independent work, but tends to muddy the waters by appearing to. If we are interested in building sound theories, rather than winning quick debates against inattentive opponents, we should hope to do more than that.