George H. Smith discusses various formulations of the non‐​aggression principle and concludes with some remarks about the problem of pollution.

George H. Smith was formerly Senior Research Fellow for the Institute for Humane Studies, a lecturer on American History for Cato Summer Seminars, and Executive Editor of Knowledge Products. Smith’s fourth and most recent book, The System of Liberty, was published by Cambridge University Press in 2013.

Most of this final part of my series is a general commentary on the non‐​aggression principle (NAP) rather than responses to specific points raised by Matt Zwolinski in “Six Reasons to Reject the Non‐​Aggression Principle.” At the end I briefly consider the problem of pollution.

According to Zwolinski, the non‐​aggression principle (NAP) “holds that aggression against the person or property of others is always wrong, where aggression is defined narrowly in terms of the use or threat of physical violence.”

As I noted in Part 1 of this series, “the NAP usually is (and should be) expressed in terms of physical force, not violence.” A possible distinction between these two terms may be illustrated as follows: Suppose a large man physically blocks the doorway of an old lady’s house and will not allow her to enter. We might say that this is not literally a violent act, since the man never comes into contact with the lady. And even if we agree that his action should reasonably be interpreted as an intent, or threat, to use violence should she attempt to enter her own house, it is the blocking of the entrance by physical means that qualifies as a violation of her property rights. Thus, in this as in many other cases, it seems more appropriate to speak of physical force rather than of violence per se.

Given that Murray Rothbard often framed the NAP in terms of “violence,” Zwolinski cannot be faulted for following his lead. But it should be kept in mind that many (and perhaps most) libertarians follow Ayn Rand in framing their fundamental political principle as the non‐​initiation of physical force (often abbreviated NIOF), rather than speaking of violence. As Rand wrote in “Man’s Rights”:

To violate man’s rights means to compel him to act against his own judgment, or to expropriate his values. Basically, there is only one way to do it: by the use of physical force.

Similarly, in “The Nature of Government,” we find this formulation:

Man’s rights can be violated only by the use of physical force. It is only by means of physical force that one man can deprive another of his life, or enslave him, or rob him, or compel him to act against his own judgment.

In Part 3, I discussed how Rothbard applied the NAP to the issue of fraud. That Rand applied her NIOF principle in essentially the same manner–as well as to other problems, such as breach of contract–is clearly indicated in this passage from “The Nature of Government.”

A unilateral breach of contract involves an indirect use of physical force: it consists, in essence, of one man receiving the material values, goods or services of another, then refusing to pay for them and thus keeping them by force (by mere physical possession), not by right–i.e., keeping them without the consent of the owner. Fraud involves a similarly indirect use of force: it consists of obtaining material values without their owner’s consent, under false pretenses or false promises. Extortion is another variant of an indirect use of force: it consists of obtaining material values, not in exchange for values, but by the threat of force, violence or injury.

Thus, as Rand put it in “Galt’s Speech”: “So long as men desire to live together, no man may initiate – do you hear me? no man may start–the use of physical force against others.”

Although Rothbard’s usage may be confusing at times, three things should be noted. First, his use of “violence” is consistent with a legalistic meaning, according to which violence is regarded as the unjust or unlawful use of physical force. The entry on “violence” in Black’s Law Dictionary reads, in part: “Force, physical force, force unlawfully exercised, the abuse of force, that force which is employed against common right, against the laws, and against public liberty.”

Second, that Rothbard intended his non‐​aggression principle to be identical with prohibiting the initiation of physical force may be seen in the fact that he sometimes used the latter phrasing–as we see in his article “Law, Property Rights, and Air Pollution, in which he depicts “the basic axiom of libertarianism” as “no initiation of force against person or property.”

Third, throughout the history of classical liberalism we sometimes see the terms “force” and violence” used more‐​or‐​less interchangeably. For example, in The Constitution of Liberty F.A. Hayek wrote that “the threat of force or violence is the most important form of coercion.”

At times, Rothbard used neither “violence” nor “force” when formulating the fundamental libertarian principle. In Man, Economy, and State, for instance, he focused on the libertarian prohibition of “invasive action,” which he defined as follows:

Invasive action may be defined as any action–violence, theft, or fraud–taking away another’s personal freedom or property without his consent.

While conceding that Rothbard formulated the NAP in various and sometimes imprecise ways, I think it is clear what he meant. Another potential source of confusion is Rothbard’s use of “axiom” in regard to the NAP. Since Rothbard attempted to provide a moral justification for the NAP (especially in The Ethics of Liberty), by “axiom” he obviously did not mean a fundamental moral principle, much less a self‐​evident moral principle. Rather, he used “axiom” to signify the fundamental political principle of a free society. Whether this was a judicious use of “axiom” is something I will leave for readers to decide.

As with many earlier libertarian thinkers, regardless of the terms they used, both Rothbard and Rand attempted to justify a theory of rights, and they then used that foundation to distinguish between voluntary and coercive interaction. As Rothbard wrote in Power and Market, “liberty is defined as freedom to control what one owns without molestation by others.” (This notion of “freedom” was squarely in the Lockean tradition, as I discussed in an earlier essay.)

Rothbard, who was well‐​versed in the history of libertarian ideas, often used “property” in the older, classical sense to mean moral jurisdiction over something. It was with this meaning in mind that James Madison spoke of property in one’s time, and an earlier Lockean, William Wollaston, spoke of property in one’s happiness. This was what Rothbard meant when, following the lead of the nineteenth‐​century libertarian Auberon Herbert, he defended “self‐​ownership” as the fundamental human right.

Rand, in contrast, preferred to speak of “the right to life” instead of “self‐​ownership,” while reserving the word “property” to denote external goods. Nevertheless, she occasionally reverted to the classical meaning of “property,” according to which to own x, or to have property in x, means to have sovereign jurisdiction over x, i.e., the right to use and dispose of x as one sees fit. In “What is Capitalism?” Rand put it this way:

Is man a sovereign individual who owns his person, his mind, his life, his work and its products—or is he the property of the tribe (the state, the society, the collective) that may dispose of him in any way it pleases, that may dictate his convictions, prescribe the course of his life, control his work and expropriate his products?

Despite the linguistic differences between Rothbard and Rand, both emphasized consent as a fundamental condition of justice in human relationships. As Rothbard put it in The Ethics of Liberty, after explaining the nature of “the free society, the society of peaceful cooperation and voluntary interpersonal relations”:

There is, however, another and contrasting type of interpersonal relation: the use of aggressive violence by one man against another. What such aggressive violence means is that one man invades the property of another without the victim’s consent. The invasion may be against a man’s property in his person–as in the case of bodily assault, and/​or against his property in tangible goods, as in robbery or trespass. In either case, the aggressor imposes his will over the natural property of another–he deprives the other man of his freedom of action and of the full exercise of his natural self‐​ownership.

Disagreements over how certain key words should be used are nothing new; we find similar discussions throughout the history of classical liberalism. An interesting and useful analysis appears in an unpublished manuscript by Jeremy Bentham (1748–1832). After dividing coercive laws into two broad categories, commands and prohibitions. Bentham continued:

In either of the two cases of command and prohibition, the person whose act it is that is in question, may be said (on account of such act) to be coerced: to be under coercion.

In the case of command he may be said to be constrained: to be under constraint.

In the case of prohibition he may be said to be restrained: to be under restraint.

When a person is neither constrained nor restrained with respect to an act, neither constrained to do it nor restrained from doing it, he is said with respect to that act to be free, to be at liberty.

Bentham concluded:

Liberty then is neither more nor less than the absence of coercion. This is the genuine, original and proper sense of the word liberty. The idea of it is an idea purely negative. . (Quoted in Douglas G. Long, Bentham on Liberty, University of Toronto Press, 1977, pp. 73–74.)

F.A. Hayek, among other classical liberals, agreed that “to be precise, we should probably define liberty as the absence of restraint and constraint”–so long as it is understood that these terms refer to the actions of human beings rather than to natural phenomena.

We now arrive, at long last, to the only point by Zwolinski that I have not yet considered, viz., pollution. Zwolinski writes:

As I noted in my last post, Rothbard himself recognized that industrial pollution violates the NAP and must therefore be prohibited. But Rothbard did not draw the full implications of his principle. Not just industrial pollution, but personal pollution produced by driving, burning wood in one’s fireplace, smoking, etc., runs afoul of NAP. The NAP implies that all of these activities must be prohibited, no matter how beneficial they may be in other respects, and no matter how essential they our to daily life in the modern industrialized world. And this is deeply implausible.

In an earlier article, “Libertarianism and Pollution,” Zwolinski explores in greater detail the possible implications of the NAP for pollution, and he cites in passing Rothbard’s most complete treatment of this issue, “Law, Property Rights, and Air Pollution,” which was originally published in the Cato Journal (Spring 1982).

At the risk of ending this series with a whimper rather than a bang, I’m afraid I have little to say about pollution and the problems it creates for the NAP. For one thing, I have not given this issue much thought over the years; for another, I think Rothbard deals quite well with the problems in his article in the Cato Journal, though I might take issue with a few minor points.

I will concede that Zwolinski is justified in raising the problem of pollution. Of his six objections to the NAP, this is the only one that is credible, in my view. But I see no justification for rejecting a strict interpretation of the NAP on the basis of one difficulty.

All general theories, including those in the hard sciences, confront unresolved problems and unanswered questions. Libertarian theory is no exception. But to call for a radical paradigm shift because of such problems, as Zwolinski does with the NAP, cannot be justified unless the dominant paradigm (to use Thomas Kuhn’s expression) experiences drastic failures in a number of areas, and unless a more satisfactory paradigm is offered in its place.

Should Zwolinski ever decide to explain his own paradigm, then we may examine its strengths and weaknesses and thereby compare it to a strict interpretation of the NAP. But no such comparative analysis is possible in a theoretical vacuum. Merely to claim that there are exceptions to the NAP does not come close to telling us what we need to know. Unless we accept Zwolinski and his fellow Bleeding Hearts as the final arbiters in this matter, we will need clearly defined criteria by which we can identify legitimate exceptions to the NAP, and distinguish them from purported exceptions that cannot be justified. Again, it will not do for Zwolinski (or anyone else) to proclaim that is an exception to the NAP unless he also explains and justifies the criteria we should use to distinguish between legitimate and illegitimate exceptions.

Meanwhile, until this groundwork has been laid and justified, I will continue to view pollution as merely one among numerous problems in libertarian theory that requires additional work.