Natural Law and the Non-Aggression Principle

Gary Chartier


The strand of libertarian thinking anchored in the work of Murray Rothbard and Ayn Rand gives pride of place, as far as political ethics are concerned, to the non-aggression principle (NAP), which holds that no one may initiate force against another person. As commonly read in libertarian circles, the principle precludes the initiation of force against someone else’s property as well as her person. (For convenience, we can call these the person-aspect and the property-aspect of the NAP.) Leonard Read (who did not, perhaps, take it quite seriously enough) famously summed up this principle by observing that it was compatible with “anything that’s peaceful.” In this post, I want to ask whether an important expositions of the natural law tradition in which Rothbard and Rand were both rooted can ground something like the NAP.

Rothbard emphasized in The Ethics of Liberty that the natural law theory he offered there was a theory of politics, that is, as he put it, of “the just use of force.” He did not intend to propose a general theory of ethics, and he stressed that serious moral questions extended well beyond questions about when force was appropriate. At the same time, he seems plausibly to have believed, it’s most important to get clear on the moral limits of violence. As long as rejecting aggression was accepted as a ground-rule, people could get along satisfactorily even if their views on other moral questions differed. That didn’t mean that all moral stances compatible with a commitment to non-aggression were equally good.

By rooting his position in the natural law tradition, Rothbard plausibly implied that political ethics was a subset of natural law ethics more broadly construed. On this view, natural law political ethics wouldn’t be seen as free-standing; rather, natural law convictions about proper limits on the use of force would flow from natural law ethics more generally. This way of thinking about the relationship between political ethics and general ethics doesn’t follow strictly, of course; perhaps there are moral principles that are concerned exclusively with the use of force and don’t depend on more general principles. But it seems more economical and elegant to suppose that, if there are more general natural law principles of ethics, principles of political ethics are intelligible and justifiable in light of those more general principles.

There are obviously multiple strands in the natural law tradition. Rothbard was especially fond of the Spanish Scholastics, whom he saw as in many ways the precursors of the Austro-libertarians. But their own thought was grounded in the earlier work of Aquinas and Aristotle. And subsequent descendants of Aquinas have reworked the Aristotelian tradition to which he was a major contributor in ways quite different from those of the Scholastics so dear to Rothbard.

The position of the contemporary “new classical natural law” theorists is an obvious example. It reflects the influence of the post-World War II analytic tradition in English-language philosophy, and is particularly dependent on the work of the late G. E. M. Anscombe. My purpose here is not to consider all of its intricacies but to consider how closely the conclusions supported by this particular variety of natural law thinking can be brought to resemble Rothbard’s in one specific way. My question is: to what extent can a plausible version of NCNL theory support something like a Rothbardian version of the non-aggression principle?

NCNL theory features two key components: basic goods and basic practical principles.

The goods are aspects of human welfare. They include life, speculative knowledge, practical reasonableness, friendship, religion, self-integration, æsthetic experience, and play. (Some heterodox NCNL thinkers—I’m one—have been inclined to include more subjective aspects of welfare, like sensory pleasure and peace of mind [thanks to Mark Murphy for the latter] on the list, and I’ve argued, too briefly, that there is good reason not to include self-integration. The details aren’t crucial.) What matters, in general, is not just what counts as a basic aspect or dimension of welfare or well being. What’s significant, instead, is that these aspects of welfare aren’t reducible to anything else (either a substantive good like pleasure or felt satisfaction, or a formal good like preference-satisfaction) and that each category and each instance of each category is incommensurable and non-fungible.

It is possible, the NCNL theorists emphasize, to choose among instances of various aspects of welfare in various combinations. And our choices are constrained by reason in two ways—to be reasonable, they must be for real goods rather than illusory ones (like emotional satisfaction untethered to objectively satisfactory states of affairs in the real world) and they must be consistent with the principles of practical reasonableness (about which more anon). But provided a choice is a choice for a real good and is otherwise consistent with the demands of practical reasonableness, there will be no objective way to rank one choice as “better” or “worse” than another (except in terms of the actor’s own prior commitments).

This basic fact of incommensurability and non-fungibility renders consequentialism a non-starter. For standard consequentialism, at least, depends on the ability to rank-order states of affairs incorporating many different aspects of welfare. And if there is no rationally inescapable way to combine all of the goods realized in a given state of affairs—as one cannot if the assignment of weights to different instances of different goods must be a matter of choice rather than of rational necessity—then there will be, can be, no objectively required ranking of states of affairs in the standard consequentialism demands. (Classical utilitarianism offers the possibility of objective ranking by focusing on the amount of pleasure embodied each possibility to be ranked; but as early as Mill it was becoming apparent that this sort of Benthamite project was inattentive to crucial aspects of the human experiences of valuation and moral judgment.)

This same fact of incommensurability grounds what we might see as a first approximation of the NAP framed in terms of NCNL theory: the Pauline Principle. The term “Pauline Principle” reflects St. Paul’s exasperated rejection (in Romans 3:8) of the notion that we might reasonably do evil to bring about good. The twist in the NCNL version of this principle, though, is that the principle is not seen as dependent on previously specified deontic norms. The idea behind the principle is often cashed in something like this way: a set of rules (say, the Ten Commandments) is treated as given; and the Pauline Principle is understood as stipulating that the rules should be treated as exceptionless, so that they may not be violated even in pursuit of particularly good consequences.

Framed this way, the principle appears unavoidably arbitrary. Why should I accept the relevant moral rules in the first place? And what reason, exactly, does the Pauline Principle give me to treat them as exceptionless?

Thus the strength of the NCNL version. The NCNL theorists don’t offer a version of the Pauline Principle that begins with a set of specific moral rules treated as givens. Rather, they derive it in large part simply from the idea that there are objective aspects of human welfare.

Their version of the Principle can be framed like this: don’t purposefully or instrumentally cause harm to any basic aspect of a moral subject’s welfare

Now, consider someone contemplating an attack on someone else’s welfare. How might the attacker reason? If her action is to be reasonable, she will need to act in order to participate in some aspect of well being or in order to foster someone else’s participation in some dimension of welfare. Presuming she correctly understands what she is doing as an attack on some aspect of someone else’s good, then she needs to see her attack as justified in virtue of the good she seeks to realize or pursue. It can’t, ex hypothesi, be because the good she’s attacking is valueless. But the good she’s attempting to realize doesn’t, couldn’t, outweigh the good she’s attacking: it’s not commensurable with it. So any purposeful attack on an acknowledged basic good in the service of another acknowledged basic good will be unreasonable, because it will involve treating a genuine good as if it weren’t a genuine good, or as if it could be rationally subordinated to another genuine good when it can’t.

Another way the point is sometimes made by NCNL theorists is to say that attacking a basic good directly amounts to the choice to make being an attacker of basic goods part of one’s identity. Thus, Grisez talks about treating oneself as giver of life and death when one chooses to attack someone’s life.

There’s obviously more to be said about this argument, and my purpose here is not to spell out all of its ramifications or to defend it against all possible objections. The point of this post is to talk about the degree to which the NCNL approach to natural law theory might be able to justify something similar to a Rothbardian NAP. But I wanted to outline the basis an NCNL theorist might offer for the Pauline Principle so it would be clear how the NCNL version differs from other versions of “Don’t do evil to bring about good.” No detailed moral principles are presupposed: all the argument needs to get off the ground is the recognition that certain aspects of welfare are, indeed, aspects of welfare and that they’re incommensurable and non-fungible.

There are multiple princples of practical reasonableness, according to the NCNL theorists. The other one that matters most for our purposes here is the Golden Rule. As the NCNLs formulate it, it amounts to: don’t make arbitrary distinctions among persons. In particular, (a) one shouldn’t make distinctions among persons except when in reasonable pursuit of intelligible aspects of human flourishing (friendship, for instance, requires distinctions between friends and non-friends) and (b) one shouldn’t, in any case, treat others—even when in otherwise reasonable pursuit of an intelligible aspect of welfare—in a way such that one would be resentful if one were treated that way oneself.

This principle, and the other practical principles that needn’t concern us here, are all, on the NCNL view, absolute and exceptionless. That is, there is never a time when it is reasonable to ignore the Golden Rule or the Pauline Principle. But there’s one fairly obvious difference between the two. The Pauline Principle rules out certain generically specifiable action-types absolutely. For example: any instance of targeting noncombatants in war-time is fairly clearly going to be an instance of purposefully causing harm to one or more basic aspects of well being. So it’s possible to be quite clear in general terms about various sorts of conduct that will always be inconsistent with the Pauline Principle. And this means, in turn, that someone potentially on the receiving end of such conduct will have an absolute right not to be subjected to the ill effects of that conduct.

Note that the Pauline Principle is quite compatible with causing unintended but foreseen harm, harm as an anticipated but unsought by-product or side-effect of action intended to realize or pursue a genuine good. (Thus, it can allow for the use of force to defend oneself or others: one’s purpose in this case needn’t be to cause harm, but simply to repel or resist an attack.) But the fact that the harm isn’t purposeful or instrumental doesn’t mean it’s automatically permissible. There will be multiple constraints on bringing about unintended harms. But the most important will be the Golden Rule (to which I’ll come in a moment): one may not impose a risk of unintended but anticipated harm on someone else if one would resent the imposition of a similar risk, in comparable circumstances, on oneself or one’s loved ones.

It’s clear that the Pauline Principle provides very solid grounding for the person-aspect of the NAP. Any purposeful or instrumental violence against a person’s body, mental health, or peace of mind will clearly be ruled out by the Pauline Principle; using force to defend oneself or others will be permissible, but imposing unreasonable risks of harm on others won’t.

It’s not as clear, though, that NCNL theory can ground the property-aspect of the NAP. That’s because property rights, from the NCNL perspective, are rooted in the Golden Rule.

Just as there’s an absolute right not to be treated in a manner inconsistent with the Pauline Principle, while there’s also an absolute right not to be treated in a manner inconsistent with the Golden Rule. But what the Golden Rule requires will vary far more from situation to situation than what the Pauline Principle requires. Thus, mid-level general norms that flow from the Golden Rule—like Keep promises or Avoid rudeness—may admit of a variety of exceptions.

The NCNL theorists begin from what they see as essentially Aristotle’s point of view: everything in principle belongs to everyone, but there are good reasons to give responsibility for each thing to someone or some group of people in particular, for the benefit of all. Their view, in effect, is that property rights flow primarily from the Golden Rule. This basic principle fairness, along with some contingent but persisten facts about human nature and the human situation, impose some limits on what might count as a just property regime. Finnis focuses primarily on three (the labels are mine):

  1. incentivization: in general, a just property system will be one that facilitates people’s contribution to the productivity of a community’s economy through the use of incentives; someone can sometimes reasonably offer the fact that a property rule would incentivize people to engage in productive activity as a reason for others to support the rule and so in support of her claim to a piece of property that would be hers under the rule.
  2. stewardship: in general, a just property system will facilitate stewardship—taking good care of property, cultivating and developing it responsibly, and preventing it from falling into disrepair; someone can sometimes reasonably offer the fact that a property rule would likely foster the effective stewardship of property as a reason for others to support the rule and so in support of her claim to a piece of property that would be hers under the rule.
  3. autonomy: in general, a just property system will be one that facilitates people’s autonomy—their freedom to determine the contours of their own lives and major life choices without intrusion by others; someone can sometimes reasonably offer the fact that a property rule would help people to be autonomous as a reason for others to support the rule and so in support of her claim to a piece of property that would be hers under the rule.

Each of these rationales is plausible and persuasive, but I suggest that several others might also be relevant, too (thanks to a variety of philosophers and social theorists for suggesting these to me):

  1. generosity: in general, a just property system will be one that makes it possible for people to be generous; someone can sometimes reasonably offer the fact that a property rule would enable people to be generous as a reason for others to support the rule and so in support of her claim to a piece of property that would be hers under the rule.
  2. reliability: in general, a just property system will enable people to rely on their expectations that otherwise just property rules will continue in force, that decisions made about individual claims in light of such rules will be respected, and that otherwise just property titles will be respected; someone can sometimes reasonably offer the fact that a property rule would honor people’s past expectations or enable them to depend on their expectations in the future as a reason for others to support the rule and so in support of her claim to a piece of property that would be hers under the rule.
  3. productivity: in general, a just property system will be one that ensures that property is put to its most productive use; someone can sometimes reasonably offer the fact that a property rule would ensure that property was put to its most productive use as a reason for others to support the rule and so in support of her claim to a piece of property that would be hers under the rule.
  4. compensation: in general, a just property system will be one that makes it possible for people to receive, and likely that they will receive, compensation for the goods and services they provide to others; someone can sometimes reasonably offer the fact that a property rule would enable people to be compensated for providing goods and services as a reason for others to support the rule, and so in support of her claim to a piece of property that would be hers under the rule.
  5. identity: in general, a just property system will take reasonable account of people’s identity-constitutive attachments to pieces of property; someone can sometimes reasonably offer the fact that a property rule would protect people’s identity-constitutive attachment to pieces of property as a reason for others to support the rule, and so in support of her claim to a piece of property that would be hers under the rule.
  6. simplicity: in general, a just property system will be one that features rules that are simple—that are easy to formulate, articulate, learn, and apply; someone can sometimes reasonably offer the fact that a property rule is simple as a reason for others to support the rule, and so in support of her claim to a piece of property that would be hers under the rule.
  7. peacemaking: in general, a just property system will be one that features rules that minimize conflict—notably by clearly allocating responsibility for particular things to particular people; someone can sometimes reasonably offer the fact that a property rule would be conflict-minimizing as a reason for others to support the rule, and so in support of her claim to a piece of property that would be hers under the rule.
  8. coordination: in general, a just property system will be one that coordinates people’s interactions by making possible the aggregation of information about their interests and needs and the determination of appropriate production patterns and distribution levels for goods and services; someone can sometimes reasonably offer the fact that a property rule would foster this kind of coordination as a reason for others to support the rule, and so in support of her claim to a piece of property that would be hers under the rule.

These additional concerns (1) add to the support for a system of private property provided by the considerations adduced by the NCNL theorists and (2) further constrain the kind of systems that could reasonably count as just.

But notice what they don’t do:

  1. They don’t, I think, leave reasonable people with a single option as regards property rules as regards either (a) acquisition or (b) the extent of control. (Thus, to take an obvious example, while I think they do count against at least radical versions of Georgism, they don’t seem to provide one for a definitive basis for deciding between Lockean and occupancy-and-use views, and they certainly leave open, say, the length of time property might need to be abandoned before title might pass to a homesteader.) They point to considerations that ought to matter when, say, a defense association or agency in a stateless society is determining which property rules to enforce, but they leave open the question just what option is finally chosen. (And this seems perfectly reasonable to me: first, some empirical facts and some implications of particular ideas are unclear and need still to be discovered or understood more fully, and experimentation among different property rules, within the constraints of justice, will facilitate greater understanding; second, different people’s personalities will obviously vary, and some people will simply be more comfortable with some rules than other people will be—and there seems no reason why they shouldn’t be able to proceed accordingly.)
  2. Then, there’s the separate point that, whatever general rules are compatible with the Golden Rule in light of these considerations, these rules won’t be exceptionless. To take an obvious example: both Aquinas and Locke explicitly acknowledged that emergencies justified violating otherwise stable, reliable property rights. Aquinas maintains that when a need is “so manifest and urgent, that it is evident that the present need must be remedied by whatever means be at hand (for instance when a person is in some imminent danger, and there is no other possible remedy) then it is lawful for a man to succor his own need by means of another’s property by taking it either openly or secretly, not is this properly speaking theft or robbery.” Aquinas fairly clearly has in mind here primarily cases like the impending avalanche example David Friedman floats inThe Machinery of Freedom. But Locke, so far from being the exemplar of “possessive individualism” Macpherson and others claimed him to be, is if anything more expansive in this regard. He writes: “charity gives every man a title to so much out of another’s plenty, as will keep him from extreme want, where he has no means to subsist otherwise” (his focus isn’t on the casuistry of emergencies, and it’s not clear to me whether he thought this norm ought to be enforceable via self-help). Locke and Aquinas both seem to see property rules as fuzzy in just the way one might expect them to be if they were rooted in a general principle of fairness like the Golden Rule.

Despite these qualifiers, it’s clear that a given legal system (say, the set of legal rules articulated and enforced by a given protective association or defense agency) could and should provide for just the sort of space for individual freedom Rothbard and others want. It’s also clear, though, that a set of property rights grounded in the Golden Rule wouldn’t yield the property-aspect of the NAP, at least if the property-aspect is understood to require acceptance of Lockean rules regarding the acquisition and maintenance of property title and to preclude any violation of an owner’s right to exercise unqualified exclusive dominion over her justly acquired property.

To put it another way: the NAP seems to imply that a person’s property in material realities external to her person should be treated as equivalent to her person, as an extension of her body. Just as it would be wrong to attack a person’s body, on this view, it would be equally wrong, and wrong for the same basic reason, to attack her property.

This is often defended by noting that justly acquired and maintained property is acquired either through the owner’s labor or as a gift from someone with ownership rights rooted in acquisition through labor. Thus, to commandeer someone’s property is in effect to commandeer her labor, and thus to make her a slave.

There’s something intuitively appealing about this equation of person and property, but it also leads to some implausible conclusions. I would be unlikely to judge that breaking into my mountain cottage to escape an avalanche was equivalent to enslaving me. I am inclined to suspect, though I won’t argue the point here, that this is because, while some objects are integrated into our identities, most are not.

In any event, the NCNL theorists clearly demarcate body and property quite clearly. They would be inclined, I think, to treat regarding one’s property as an extension of oneself as an instance of fetishization. That doesn’t mean, though, that they couldn’t come to endorsing something like the property-aspect of the NAP. Several aspects of the NCNL view are relevant to this conclusion.

  1. The basic fairness considerations embodied in the Golden Rule will count against the cost shifting represented by many of the property regulations the NAP is rightly seen as attacking. Most people will resent being asked to pay for the realization of other people’s æsthetic or cultural preferences or to pay for services they could obtain more inexpensively on the market; and, if they do, they will be unreasonable if they ask other people to to do so. More generally, whatever judgments people tend to make about their own property rights will be judgments fairness will demand that they accept when reaching conclusions about others’.
  2. Our participation in basic goods will characteristically involve the use of property. Attacks on someone’s property will sometimes be ruled out precisely because they are also purposeful or instrumental attacks on basic goods.
  3. Similarly, people often protect their property using their bodies, and attacks on their property will thus sometimes be inappropriate precisely because it involves using force purposefully or instrumentally in ways that harm people’s bodies.
  4. Acting out of hostility toward someone by harming her or his property will obviously be ruled out.
  5. As I have suggested, the overlapping considerations I have adduced in support of a property rights regime tend to tilt in the same direction, and so to provide strong justification for largely undisturbed property rights. Someone who may quite reasonably not resent one sort of imposition on her property may well resent another, and so be precluded from engaging in or supporting a similar sort of imposition on someone else’s.

These considerations seem clearly to support a set of robust property rights, even if they are likely to prove consistent with a broader range of rights than those characteristically defended by Rothbardians. Adding strength to the protections they seem likely to afford is the fact that, as I’ve already noted, the NCNL theorists offer a set of rock-solid arguments against classical utilitarianism and its various consequentialist cousins: global consequentialism is, they show persuasively, incoherent. That doesn’t mean, of course, that expected consequences are never relevant to deliberation about reasonable action; but their reasonableness is to be guaged in light of the Golden Rule rather than in terms of a putatively objective metric that allows a “best overall state of affairs” to be identified. Lots of different options are consistent with the demands of reason.

For the NCNLs, however, this very open-endedness provides a justification for the existence of the state, and so for some restraints on property. The coordination of the actions of people in a situation in which there is no single best choice requires, they maintain, that someone articulate and enforce ground-rules, and people are obligated to obey whoever seems most likely to be able to do this effectively. Because—according to the NCNLs—people are responsible for contributing to worthwhile causes and helping others, the state is free to make them do so when they do not seem inclined to do so themselves.

In effect, the NCNLs seem to argue, the Golden Rule that justifies respect for property also justifies its limitation by the state (since it is largely the Golden Rule that is seen as lying behind the state’s claim to authority).

The NCNLs are very clear that there is no natural right to rule. No one is inherently in charge of anyone else. However, their concern for order leads them to believe that it is reasonable for some people to accept the authority of others, and so for some people to assert authority over others, to ensure that social interaction is stable and appropriately structured.

The rejection of a natural right to rule places a very large question mark against the claims of any authority figure. So, too, does the Golden Rule, insofar as most people do not relish subjection to others’ authority, and so act unreasonably when they assert authority over others, and insofar as state-made law would seem frequently to interfere with the property rights that flow from the operation of rules reasonably reflective of the considerations I adduced earlier in support of a property system, rules the Golden Rule would give most people in most situations good reason to endorse.

The success of the NCNLs’ argument for state authority depends, in short, on the implicit view that the state is needed to preserve social order and coordinate social interaction. But there is ample evidence that people can organize themselves peacefully without the state’s supervision, and ample theoretical support from economists and biologists for the view that we should expect them to be able to do so. So it is difficult to see why endorsing the Golden Rule should require support for the existence and operation of any state.

In addition, there is also ample evidence that states are profoundly wasteful—costing far more than non-state actors performing similar tasks would cost—and destructive—causing enormous human loss through war and repression. There are also excellent reasons to expect generally bad behavior on the part of states in light of the probability that those most likely to come to occupy leadership positions in states will be ambitious and power-hungry; that even decent people will readily be corrupted both by the opportunities power presents and by special interests able to concentrate on wooing them; and that even those who lack their integrity will be unable to match the distributed intelligence of free people engaged in voluntary cooperation.

Finally, the NCNLs’ argument for the state seems limited insofar as it presumes that the state is well-equipped to determine how much people ought to give to worthwhile projects, and to which projects they ought to give. Since the relevant duty is, in the Kantian sense, imperfect—that is, it is precise neither as to quantity nor as to recipient—there is something deeply arbitrary about the state’s presuming to enforce particular ways of fulfilling it. And attempts to enforce particular ways of fulfilling seem unavoidably likely to prompt a struggle for the largesse the state proposes to dispense that will only increase the odds of corruption.

In short, the Golden Rule need not be seen as providing any support for the authority of the state, once it is apparent that alternatives to the state are readily conceivable and that the state is a source of enormous mischief.

My own heterodox version of NCNL theory, as articulated here in contrast to the version defended by the orthodox NCNL theorists, does not yield a simple, straightforward version of the NAP or a simple, straightforward argument for anarchism. NCNL theory gives pride of place to an account of human flourishing and a set of basic practical principles. Taking human welfare seriously and acting on the practical principles does lead to respect for a robust, if not fully determinate, set of property rights and provides, contrary to the NCNL theorists’ own evident view, little reason to approve of the existence and operation of an entity with the authority to attack people’s bodies or take their property.

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