Principle of non-aggression

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The non-aggression principle (also called the non-aggression axiom, or the anti-coercion or zero aggression principle or non-initiation of force) is an ethical stance which asserts that "aggression" is inherently illegitimate. "Aggression" is defined as the "initiation" of physical force against persons or property, the threat of such, or fraud upon persons or their property. In contrast to pacifism, the non-aggression principle does not preclude violent self-defense. The principle is a deontological (or rule-based) ethical stance.


The principle has a long tradition but has been mostly popularized by market anarchists and other schools of libertarianism (consequentialist libertarians do not base their libertarianism on it).[1] It is an axiom of some forms of anarchism, and traces of it can be found in Judaism, Christianity, and Islam, as well as in Eastern philosophies such as Taoism.[2]


Libertarians typically claim that the non-aggression principle includes property and freedom of contract as a part of self-ownership. The basis for this extension of self-ownership to one's property is John Locke's argument (also called the homestead principle) that mixing of labor with an unowned resource makes that resource part of one's self. Subsequent exchange of such property (e.g. sale, rental) simply transfers this right. Hence, to aggress against someone's property is to aggress against the individual. As for freedom of contract, the right of self-ownership is held to imply freedom of action in the absence of aggression (e.g. in the absence of false or duress contracts, and the absence of contracts stipulating aggression against third-parties).


If these two rights to private property and to freedom of contract are taken as given, then the non-aggression principle is held by its supporters to lead to the rejection of theft, vandalism, assault, fraud, pollution and the concept of victimless crimes.

When applied to the state, it has been taken to prohibit many policies including taxation, the military draft, regulation of voluntary exchange and individual participation in non-defensive state wars. When taken to the logical conclusion, anarchists argue that it calls for abolition of the state itself, asserting that individuals would be protected from aggression by what amount to insurance contracts with private organizations, through a militia union, or completely by self-defense. This proposed system resembles fire protection services in colonial Philadelphia.

The United States Libertarian Party and others view it as an essential tenet of all libertarian thought.


The principle has been derived by various philosophical approaches, including:

Historical formulations and background

Historical formulations of the non-aggression principle
Year Formulated by Formulation
300's BC Epicurus "Natural justice is a symbol or expression of usefullness, to prevent one person from harming or being harmed by another."[4]
900's Abu Mansur Al Maturidi, Ibn Qayyim Al-Jawziyya, Averroes These Islamic theologians and philosopher wrote that man could rationally know that man had a right to life and property.
early 1200's Ibn Tufayl In Hayy ibn Yaqzan the Islamic philosopher discussed the life story of a baby living alone without prior knowledge who discovered natural law, and natural rights, which obliged man not to coerce against another's life or property. Ibn Tufayl influenced Locke's notion of Tabula Rasa.[5]
1689 John Locke In Second Treatise on Government he wrote "Being all equal and independent, no one ought to harm another in his life, health, liberty, or possessions."[6]
1682 Samuel von Pufendorf In On the Duty of Man and Citizen he wrote "Among the absolute duties, i.e., of anybody to anybody, the first place belongs to this one: let no one injure another. For this is the broadest of all duties, embracing all men as such."[7]
1722 William Wollaston In The Religion of Nature Delineated he formulated "No man can have a right to begin to interrupt the happiness of another." This formulation emphasized "begin" to distinguish aggressive disturbances from those in self-defense ("...yet every man has a right to defend himself and his against violence, to recover what is taken by force from him, and even to make reprisals, by all the means that truth and prudence permit.")
1790 Mary Wollstonecraft ("Vindication of the Rights of Men") "The birthright of man ... is such a degree of liberty, civil and religious, as is compatible with the liberty of every other individual with whom he is united in a social compact, and the continued existence of that compact."[8]
1816 Thomas Jefferson "Rightful liberty is unobstructed action according to our will within limits drawn around us by the equal rights of others. I do not add 'within the limits of the law', because law is often but the tyrant's will, and always so when it violates the rights of the individual." and "No man has a natural right to commit aggression on the equal rights of another, and this is all from which the laws ought to restrain him." (Thomas Jefferson to Francis Gilmer, 1816)
1851 Herbert Spencer The law of equal freedom: "Every man is free to do that which he wills, provided he infringes not the equal freedom of any other man." This notion of equal freedom goes back to earlier liberal thought.
1859 John Stuart Mill The harm principle formulated in On Liberty, states that "the only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others".
1961 Ayn Rand In an essay called "Man's Rights" in the book "The Virtue of Selfishness" she formulated "The precondition of a civilized society is the barring of physical force from social relationships. ... In a civilized society, force may be used only in retaliation and only against those who initiate its use."[9][10][11] Note that she stipulated the context - civilized society.
1963 Murray Rothbard "No one may threaten or commit violence ('aggress') against another man's person or property. Violence may be employed only against the man who commits such violence; that is, only defensively against the aggressive violence of another. In short, no violence may be employed against a nonaggressor. Here is the fundamental rule from which can be deduced the entire corpus of libertarian theory." Cited from "War, Peace, and the State" (1963) which appeared Egalitarianism as a Revolt Against Nature and Other Essays[12]
L. Neil Smith The libertarian science fiction writer claims, "No one has the right, under any circumstances, to initiate force against another human being, nor to delegate its initiation." This is considered an imprecise formulation, since it explicitly ignores context.
Walter Block "It shall be legal for anyone to do anything he wants, provided only that he not initiate (or threaten) violence against the person or legitimately owned property of another."[13]

Natural law theorist Murray Rothbard traces the non-aggression principle to natural law theorist St. Thomas Aquinas and the early Thomist scholastics of the Salamanca school [3].

Early formulations that use terms such as "harm" or "injury," such as those of Epicurus and Mill above, are today generally considered imprecise. "Harm" and "injury" are too subjective; one man's harm may be another man's benefit. For example, a squatter may make "improvements" that the owner considers detrimental. Modern formulations avoid such subjectivity by formulating the NAP in terms of individual rights or observable conduct (initiation of force/violence).


The non-aggression principle faces three kinds of criticism: the first holds that the principle is immoral, the second argues that it is impossible to apply consistently in practice, while the third holds that the interpretation of the principle is too ambiguous to be useful; respectively, the consequentialist criticism, the inconsistency criticism, and the ambiguity criticism.

Consequentialist criticism

This moral criticism is based on consequentialist ethics, usually utilitarianism. It holds that the non-aggression principle is unethical because it opposes the initiation of force even when the results of such initiation would be better than the results of any other course of action. Suppose, for instance, that you could save a million lives by killing one innocent man. The non-aggression principle holds that you should not kill that man. But this leads to a million deaths. While such extreme situations are unlikely, opponents of the non-aggression principle argue that milder forms of the same dilemma (for example the choice between taking away part of a wealthy man's property or allowing a poor person to starve) are very common. Of course, many formulations, such as Rothbard's and Block's, avoid this objection by either specifying that the NAP only applies to a civilized context (and not 'lifeboat situations')[14] or that it applies only to legal rights (as opposed to general morality.) Thus a starving man may, in consonance with general morality, break into a hunting cabin and steal food, but nevertheless he is aggressing, i.e. violating the NAP, and (by most rectification theories) should pay compensation.

Some consequentialist libertarians promote the non-aggression principle by basing its advocacy on forms of consequentialism such as rule utilitarianism and rule egoism. These utilitarians do not believe that it is categorically immoral to engage in aggression, but because they believe situations where aggression would lead to the best consequences are rare, they promote the non-aggression principle with the justification that if others accept it as a rule it would lead to better consequences than if they did not accept it as a rule. They believe the consequences of advocating the rule are superior to advocating that other individuals attempt to calculate each of their own actions to determine whether aggression or non-aggression would lead to better consequences. Other consequentialist libertarians do not promote the non-aggression principle at all; they simply believe that allowing a very large scope of political and economic liberty results in the maximum well-being or efficiency for a society, even if securing this liberty involves some governmental actions that would be considered violations of the non-aggression principle. It just so happens that these actions are limited in the free society they envision. This type of libertarianism is associated with Ludwig von Mises and Friedrich Hayek.[15]

Inconsistency criticism

The second type of criticism focuses on the difficulty of determining who exactly initiated force in many real-life conflicts. As a general rule, each side in a conflict claims that the other "started it". Sometimes it is plainly clear who initiated force - for example, when a mugger demands a person's wallet. Other times, however, the situation is more complicated. For example, one side may have been the first to threaten force and the other side may have been the first to actually use force, or the conflict began such a long time in the past that no one remembers who started it. Wars are a particularly difficult case, because very few of them begin with a country openly declaring that it wants to initiate force on another.

Libertarians usually respond by stating that such pragmatic issues are well dealt with already in today's legal systems. For instance, an example of a dissipative game is a situation where a person starts insulting another in a bar, the other person responds by shoving, the other throws a punch, and the situation dissipates into a fight. In such cases, both parties are simply guilty of aggression toward the other because the aggression clearly went beyond self defense.[citation needed]

A version of this second criticism is often upheld by libertarian socialists and others, who claim that almost every patch of land on Earth was stolen (i.e. obtained through initiation of force) at some point in its history. The stolen land was later inherited or sold until it reached its present owners. Thus, property over land and natural resources is based on the initiation of force. Among those who make this argument, some (such as followers of Henry George) claim that private property over natural resources is unique in being based on the initiation of force, while others hold that, by extension, private property over all goods derives from violence, because natural resources are required in the production of all goods.

Libertarians often reply to the "who started it?" problem by contending that the difficulty in determining who is the transgressor should not dissuade us from engaging in that process.

Furthermore, libertarians often reply to either variant of this last point with the "water under the bridge" argument: that transgressions of the past cannot all be rectified, and that an act of theft which happened very long ago can reasonably be ignored - since it is irrelevant to people living today. This, however, can generate more charges of inconsistency, because it implies that peaceful possession of property in the present legitimizes theft and/or trespass in the past – the principle known in some contexts as "squatters' rights" and in other contexts as "the right of adverse possession". This requires a "cutoff" point: a point in time when illegitimate property becomes legitimate property. Opponents argue that any such point is arbitrary.

One prominent anarcho-capitalist theorist, Murray Rothbard, argued that much private property in the U.S. southwest ought to be taken from its present private owners, and given to the lawful heirs of those who had claim to it under Mexican law before the Mexican–American War, although he also regarded this case as historically unique.

Another reply can be made on the basis of the existence of proof of possession and individuality of owners. That is: if current heirs of long dead property owners can identify the property that has been stolen and prove that the owner has passed down to him or her his initial right of property - then those persons must be recognized as the rightful owners. This is similar to the "innocent until proven guilty" proposition of modern law, that owners should be regarded as legitimate until proven differently.

Chris Cantwell argues, "[T]he NAP is quickly becoming as meaningless as the nihilists say it is. A meaningless term, subject to an infinite number of different interpretations. Building societies around it is completely hopeless, because based on how many negative messages a Facebook page gets, so does the interpretation of the NAP change."[16]

Ambiguity criticism

In addition to the above two kinds of criticism, there is also a debate around the manner in which libertarians typically interpret the non-aggression principle. Specifically, some libertarians see taxes as a form of government aggression. However, unless their libertarianism is of such an absolute degree that it opposes any kind of state, some consider taxation as a "necessary evil." They may argue that because of the free-rider problem, enough funds would not be obtainable by voluntary means to protect individuals from aggression of a greater severity. Hence, they will accept taxation as long as no more is levied than is necessary to optimise protection of individuals against aggression (from other individuals and from government itself). On the other hand, many libertarian anarchists, as strict adherents to the non-aggression principle, argue that security should be maintained by voluntary payment to private defense forces, rather than taxation. Both anarchists and opponents of libertarianism in general have made the argument that the non-aggression principle, if embraced in a pure or absolute sense, forbids the existence of states. Anarchists use this argument in their attempts to convert other libertarians to their views, while opponents of libertarianism use it to support the claim that consistent application of libertarian principles would result in the complete abolition of the state - which, in their view, is an extremist and absurd position to hold.

Some radical libertarians argue that minarchism stemming from the non-aggression principle is logically inconsistent, and consider anarchism to be the natural-rights doctrine applied in full. Others feel that minarchism from a consequentialist libertarian perspective is more cogent and a better alternative to rights-libertarian minarchism.

Social contract

There are many who oppose the libertarian idea that taxation is a form of aggression on social contract grounds. Specifically, advocates of most social contract theories see taxes as analogous to contract fees, and tax-collecting governments as agents of an (implicit) agreement among the members of a society to share certain common burdens. However, Herbert Spencer argues that: "If every man has freedom to do all that he wills, provided he infringes not the equal freedom of any other man, then he is free to drop connection with the state - to relinquish its protection and to refuse paying toward its support. It is self-evident that in so behaving he in no way trenches upon the liberty of others, for his position is a passive one, and while passive he cannot become an aggressor. It is equally self-evident that he cannot be compelled to continue one of a political corporation without a breach of the moral law, seeing that citizenship involves payment of taxes; and the taking away of a man's property against his will is an infringement of his rights" [4]. Some social contract supporters argue that a person is obliged to adhere to the "social contract" by staying within the confines of a state. Rebuttals to this view often turn on whether there is a genuine choice, whether there is a possibility to "opt out." One possible obstacle is that leaving a country can be difficult and require sacrifice, especially in the case of state-controlled borders (e.g. through the use of border guards, dogs, and walls). Another take on the issue might be that a contract implies willful adherence. Laws of the state are, by their definition, imposed. A state can be compared to the Mafia, from this perspective; meaning that people are 'free' to pay protection tax, but they are still coerced. Other libertarians point out that, as long as all the land on Earth is administered by states, a person may not exit a state without entering another state and, hence, opting out of a social contract would be impossible unless one decides to live in the ocean. Supporters of social contract theories, on the other hand, argue that opting out of many contracts that libertarians do not oppose is also difficult. For example, if a private corporation owned the water supply in a region (see "Monopoly"), and disgruntled residents of the region found it impossible to establish a new entrant in that market, then the revocation of one's contract with that corporation would mean that one would have to move out of the region. Thus, the argument goes, one's contract with the water corporation is very similar to a social contract.

Inspired by such considerations, some minarchists have suggested establishing social contracts (and taxes or "fees") only at local or regional levels, the smaller the better, since leaving a neighborhood, for example, is less burdensome and is much better at preserving freedom of choice, than having to leave an entire country. Such a system also introduces an element of competition among the various taxing entities to which a monopolistic central government does not have to answer. On the other hand, this system also makes it difficult to undertake any sort of large-scale public project, since an agreement between different regional governments would be needed. The additional challenges would limit the implementation of large-scale public projects to only those with widespread support, perhaps consolidated through an umbrella organization of smaller governments (e.g., the United Nations, European Union, North American Free Trade Agreement, North Atlantic Treaty Organization). Furthermore, lacking a centralized point of taxation control, this system also allows for the creation of "tax havens": if a certain region has little or no local taxes, many of the rich people from neighboring regions may move to it, thus depriving their original home regions of tax revenue. Whether this is good or bad depends on one's political views.

Of course, the existence of a social contract, much like the non-aggression principle, is itself a matter of dispute among the advocates of different political ideologies and views. Many libertarians argue that no contract can exist without conscious and voluntary assent by all participants. American individualist anarchist Lysander Spooner is a noted proponent of this view, while espousing the non-aggression principle as natural law. Spooner holds that the fact that governments hold the threat of force over the heads of those who would not pay taxes, any supposed social contract to pay taxes would not be legitimate since legitimate contracts can only be made in the absence of coercion (i.e., they must be voluntary).

Others argue that a social contract can indeed exist, but that it is an implicit contract between individuals to adhere to the non-aggression principle; these argue that taxation is therefore a violation of the social contract. For example, anarchist Pierre-Joseph Proudhon maintains that rather than being a contract between man and government, the "social contract is an agreement of man with man; an agreement from which must result what we call society" to "abdicate all pretension to govern each other."


  1. What's Right vs. What Works (pdf, p. 31). Charles Murray, David Friedman, David Boaz, and R.W. Bradford. Liberty. January 2005, Vol 15, No 1
  2. Libertarianism in Ancient China Murray N. Rothbard Libertarianism in Ancient China
  3. A Positive Account of Property Rights. David Friedman. Originally published in Social Philosophy & Policy, volume 11, number 2 (Summer 1994), published by Cambridge University Press.
  4. [1]
  5. G. A. Russell (1994), The 'Arabick' Interest of the Natural Philosophers in Seventeenth-Century England, pp. 224-239, Brill Publishers, ISBN 9004094598.
  8. [2]
  14. Rothbard, Murray. "Lifeboat Situations". Retrieved 2010-05-13. 
  15. Barry, Norman P. Review Article:The New Liberalism. B.J. Pol. S. 13, p. 93

Notes and references

  1. ^ Source: (Walter Block 2003)
  2. ^ Source: (Walter Block 2001)
  3. ^ Murray N. Rothbard, in "War, Peace, and the State"
  4. ^ Libertarian Party Membership Form

See also