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The non-aggression principle (or NAP, also called the non-aggression axiom, the anti-coercion, zero aggression principle or non-initiation of force) is an ethical stance which asserts that "aggression" is inherently illegitimate. "Aggression", for the purposes of NAP, is defined as initiating or threatening the use of any and all forcible interference with an individual or individual's property. In contrast to pacifism, the non-aggression principle does not preclude violent self-defense. The NAP is considered to be a defining principle of libertarianism.
- 1 History
- 2 Justifications
- 3 Definitional issues
- 4 Support and criticism
- 4.1 Moral criticisms
- 4.2 Inconsistency criticisms
- 5 See also
- 6 References
- 7 External links
The non-aggression principle has existed in various forms. Although the principle has been traced back as far as antiquity, it was first formally described by this name by the Objectivist philosopher Ayn Rand, and then further popularized by libertarian thinkers.
A number of authors have created their own formulation of the non-aggression principle, as shown in the table below.
|1689||John Locke||Locke gives the following version of the NAP: "Being all equal and independent, no one ought to harm another in his life, health, liberty, or possessions."|
|1816||Thomas Jefferson||Jefferson describes the NAP in a letter to Francis Gilmer: "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."|
|1851||Herbert Spencer||Spencer formulates the NAP as: "Every man is free to do that which he wills, provided he infringes not the equal freedom of any other man."|
|1859||John Stuart Mill||In his book On Liberty Mill states the NAP as follows: "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".|
|1923||Albert Jay Nock||In the second chapter of his book, Our Enemy, the State, Nock refers to an ancient formulation of the NAP by the legendary king Pausole, who stated it as two laws. The first law was "hurt no man" and the second was "then do as you please".|
|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."|
|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 in Egalitarianism as a Revolt Against Nature and Other Essays|
The principle has been derived by various philosophical approaches, including:
- Argumentation ethics: Some modern libertarian thinkers ground the non-aggression principle by an appeal to the necessary praxeological presuppositions of any ethical discourse, an argument pioneered by libertarian scholar Hans Hermann Hoppe. They claim that the act of arguing for the initiation of aggression, as defined by the non-aggression principle is contradictory. Among these are Stephan Kinsella and Murray Rothbard.
- Consequentialism: Some advocates base the non-aggression principle on rule utilitarianism or rule egoism. These approaches hold that though violations of the non-aggression principle cannot be claimed to be objectively immoral, adherence to it almost always leads to the best possible results, and so it should be accepted as a moral rule. These scholars include David Friedman, Ludwig von Mises, and Friedrich Hayek.[not in citation given]
- Christian worldview: There is an emerging Biblical argument that the natural rights of Locke, Rothbard and others are most truly derived from the Biblical principles of self-stewardship and the image of God in man. (In contrast, some ethicists and anthropologists of religion posit that Biblical principles are merely instances of moral systems that have evolved in different places with some common features.) The rights to life, liberty and property derive from the fact that God has granted each person to be the steward of himself and none other, granting him the human authority to manage his own life and property, which morally requires him to do so according to God's Law, but civilly requires him to respect the dignity and property rights of his neighbor. The Biblical purpose of civil government is to serve on behalf of individuals who have had their life, liberty, or property violated by another.
- Natural rights: Some derive the non-aggression principle deontologically by appealing to rights that are independent of civil or social convention. Such approaches often reference self-ownership, ethical intuitionism, or the right to life. Thinkers in the natural law tradition include Lysander Spooner, Murray Rothbard, and Robert Nozick.
- Objectivism: Ayn Rand rejected natural or inborn rights theories as well as supernatural claims and instead proposed a philosophy based on observable reality along with a corresponding ethics based on the factual requirements of human life in a social context. She stressed that the political principle of non-aggression is not a primary and that it only has validity as a consequence of a more fundamental philosophy. For this reason, many of her conclusions differ from others who hold the NAP as an axiom or arrived at it differently. She proposed that man survives by identifying and using concepts in his rational mind since "no sensations, percepts, urges or instincts can do it; only a mind can." She wrote, "since reason is man's basic means of survival, that which is proper to the life of a rational being is the good; that which negates, opposes or destroys it [i.e. initiatory force or fraud] is the evil."
- Estoppel: Stephan Kinsella believes that the legal concept of estoppel implies and justifies the non-aggression principle.
Many supporters and opponents of abortion rights justify their position on NAP grounds. One important question to determine whether or not abortion is consistent with NAP is at what stage of development a fertilized human egg cell can be considered a human being with the status and rights attributed to personhood. Some supporters of NAP argue this occurs at the moment of conception. Others argue that since they believe the fetus lacks sentience until a certain stage of development, it does not qualify as a human being, and as such may be considered property of the mother. Opponents of abortion, on the other hand, state sentience is not a qualifying factor. They refer to the animal rights discussion and point out the Argument from marginal cases that concludes NAP also applies to non-sentient (i.e. mentally handicapped) humans.
Another important question is whether an unwelcome fetus should be considered to be an unauthorized trespasser in its mother's body. The non-aggression principle does not protect trespassers from the owners of the property on which they are trespassing. It can also be argued that unwelcome fetuses are themselves committing aggression against their mothers, by taking materials (oxygen, water, nutrients) from her bloodstream, by injecting toxic metabolic end-products (carbon dioxide and creatinine) into her bloodstream, and by preparing to subject her to major medical/surgical trauma in the form of full-term labor and delivery.
Objectivist philosopher Leonard Peikoff has argued that a fetus has no right to life inside the womb because it is not an "independently existing, biologically formed organism, let alone a person." Pro-choice libertarian Murray Rothbard held the same stance, maintaining that abortion is justified at any time during pregnancy if the fetus is no longer welcome inside its mother. Likewise, other pro-choice supporters base their argument on criminal trespass. In that case, they claim, NAP is not violated when the fetus is forcibly removed, with deadly force if need be, from the mother’s body, just as NAP is not violated when an owner removes from the owner’s property an unwanted visitor who is not willing to leave voluntarily. Libertarian theorist Walter Block follows this line of argument but makes a distinction between evicting the fetus prematurely so that it dies and actively killing it (see Libertarian perspectives on abortion).
Pro-life libertarians, however, argue that because the parents were actively involved in giving life to another human being and the fetus was brought inside the mother’s body without his or her consent, the fetus is in the womb by necessity and no parasitism or trespassing is involved (see also legal necessity). They state that as the parents are responsible for the fetus's position, NAP would be violated when the fetus is killed with abortive techniques.
Intellectual property rights
NAP is defined as applicable to any unauthorized actions towards a person’s physical property. Supporters of NAP disagree on whether it should apply to intellectual property (IP) rights as well as physical property rights. Some argue that because intellectual concepts are non-rivalrous, intellectual property rights are unnecessary. while others argue that intellectual property rights are as valid and important as physical ones.
Though NAP is meant to guarantee an individual’s sovereignty, libertarians greatly differ on the conditions under which NAP applies. Especially unsolicited intervention by others, either to prevent society from being harmed by the individual’s actions or to prevent an incompetent individual from being harmed by his or her own (in)actions, is an important issue. The debate centers on topics like the age of consent for children, intervention counseling (i.e. for addicted persons, or in case of domestic violence), involuntary commitment and involuntary treatment with regards to mental illness, medical assistance (i.e. prolonged life support vs euthanasia in general and for the senile or comatose in particular), human organ trade, state paternalism (including economic intervention) and foreign intervention by states. Other discussion topics on whether intervention is in line with NAP include nuclear weapons proliferation, and human trafficking and (illegal) immigration.
Supporters generally argue that NAP only applies to humans, because humans generally have a free will and a self-conscious and rational mind, as well as a moral understanding. Most humans can therefore understand NAP and can be held accountable for their actions. Some critics claim that although these abilities are common they are not universal characteristics of the species. Young children and mentally handicapped persons may not have them (e.g. a person in a coma). When NAP applies to them as well as to normal people, as supporters of NAP agree, critics state that logically NAP should apply to all life forms with similar characteristics (see the Argument from Marginal Cases). This stance would lead to similar rights for sufficiently intelligent animals.
Some libertarians justify the existence of a minimal state on the grounds that anarchism implies that the non-aggression principle is optional because the enforcement of laws is open to competition. They claim competing law enforcement would always result in war and the rule of the most powerful.
Anarcho-capitalists usually respond to this argument that this presumed outcome of coercive competition (e.g. PMCs or PDAs that enforce local law) is not likely because of the very high cost, in lives and economically, of war. They claim that war drains those involved and leaves non-combatant parties as the most powerful, economically and militarily, ready to take over. Therefore, anarcho-capitalists claim that in practice, and in more advanced societies with large institutions that have a responsibility to protect their vested interests, disputes are most likely to be settled peacefully. Anarcho-capitalists also point out that a state monopoly of law enforcement does not necessarily make NAP present throughout society as corruption and corporatism, as well as lobby group clientelism in democracies, favor only certain people or organizations. Anarcho-capitalists aligned with the Rothbardian philosophy generally contend that the state violates the non-aggression principle by its very nature because, it is argued, governments necessarily use force against those who have not stolen private property, vandalized private property, assaulted anyone, or committed fraud.
Proponents of the NAP see taxes as a violation of NAP, while critics of the NAP argue that because of the free-rider problem in case security is a public good, enough funds would not be obtainable by voluntary means to protect individuals from aggression of a greater severity. The latter therefore accept taxation, and consequently a breach of NAP with regard to any free-riders, as long as no more is levied than is necessary to optimise protection of individuals against aggression. Geolibertarians, who following the classical economists and Georgists adhere to the Lockean labor theory of property, argue that land value taxation is fully compatible with the NAP.
Anarcho-capitalists argue that the protection of individuals against aggression is self-sustaining like any other valuable service, and that it can be supplied without coercion by the free market much more effectively and efficiently than by a government monopoly. Their approach, based on proportionality in justice and damage compensation, argues that full restitution is compatible with both retributivism and a utilitarian degree of deterrence while consistently maintaining NAP in a society. They extend their argument to all public goods and services traditionally funded through taxation, like security offered by dikes.
Support and criticism
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Supporters of the NAP often appeal to it in order to argue for the immorality of theft, vandalism, assault, and fraud. Compared to nonviolence, the non-aggression principle does not preclude violence used in self-defense or defense of others. Many supporters argue that NAP opposes such policies as victimless crime laws, taxation, and military drafts. NAP is the foundation of libertarian philosophy.[unreliable source?]
NAP faces two kinds of criticism: the first holds that the principle is immoral, and the second argues that it is impossible to apply consistently in practice; respectively, consequentialist or deontological criticisms, and inconsistency criticisms. Libertarian academic philosophers have noted the implausible results consistently applying the principle yields: for example, Professor Matt Zwolinski notes that, because pollution necessarily violates the NAP by encroaching (even if slightly) on other people's property, consistently applying the NAP would prohibit driving, starting a fire, and other activities necessary to the maintenance of industrial society.
NAP does not allow for positive rights
Critics argue that the non-aggression principle is not ethical because it opposes the initiation of force even when they would consider the results of such initiation to be morally superior to the alternatives that they have identified. In arguing against the NAP, philosopher Matt Zwolinski has proposed the following scenario: "Suppose that by imposing a very, very small tax on billionaires, I could provide life-saving vaccination for tens of thousands of desperately poor children. Even if we grant that taxation is aggression, and that aggression is generally wrong, is it really so obvious that the relatively minor aggression involved in these examples is wrong, given the tremendous benefit it produces?"
Supporters of NAP state that the absolute character of NAP is essential to maintaining property rights and individual freedom, and that by breaking it, one neglects to explore alternative solutions that do not violate the NAP, and which may have not yet been considered. Supporters of this principle maintain that any digression from it would make property rights and individual freedom subjective and introduce some form of slavery or immoral compulsion. Supporters claim that at the heart of the matter is mutual consent and that this can only be achieved if NAP is upheld.
Incompatibility with driving and other civilizational necessities
Zwolinski also notes that the NAP is incompatible with any practice that produces any pollution, because pollution encroaches on the property rights of others. Therefore, the NAP prohibits both driving and starting fires. Citing Professor David Friedman, Professor Zwolinski notes that the NAP is unable to place a sensible limitation on risk-creating behavior. Writes Zwolinski,
Of course, almost everything we do imposes some risk of harm on innocent persons. We run this risk when we drive on the highway (what if we suffer a heart attack, or become distracted), or when we fly airplanes over populated areas. Most of us think that some of these risks are justifiable, while others are not, and that the difference between them has something to do with the size and likelihood of the risked harm, the importance of the risky activity, and the availability and cost of less risky activities. But considerations like this carry zero weight in the NAP’s absolute prohibition on aggression. That principle seems compatible with only two possible rules: either all risks are permissible (because they are not really aggression until they actually result in a harm), or none are (because they are). And neither of these seems sensible.
However, supporters of NAP claim that any risky activity will be regulated by the free market when NAP is upheld. I.e. driving on a highway would involve risks but all parties involved (road owner, car drivers, passengers, insurance companies, neighbours) would have agreed upon the level of these risks for the highway to be economically viable. The road owner might require drivers to have a driving license and insurance, as well as certified vehicles. People living near the highway would have been compensated for the pollution and noise. If compensation or anti-pollution measures cost too much the highway will be built elsewhere, or not at all. Similar for flying, or polluting industries. Insurance companies will put a premium on all risky activities, making them either economically viable or not possible.
Innocent persons problem
Some critics use the example of the trolley problem to invalidate NAP. In case of the runaway trolley, headed for five victims tied to the track, NAP does not allow a trolley passenger to flip the switch that diverts the trolley to a different track if there is a person tied to that track. That person would have been unharmed if nothing was done, therefore by flipping the switch NAP is violated. Another example often cited by critics is human shields.
Some supporters argue that no one initiates force if their only option for self-defense is to use force against a greater number of people as long as they were not responsible for being in the position they are in. Murray Rothbard's and Walter Block's formulations of NAP avoid these objections by either specifying that the NAP applies only to a civilized context (and not 'lifeboat situations') 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. Critics argue that the legal rights approach might allow people who can afford to pay a sufficiently large amount of compensation to get away with murder. They point out that local law, though based on NAP, may vary from proportional compensation to capital punishment to no compensation at all.
Supporters generally argue that any harm done to innocent persons or any other collateral damage in these cases is done by whoever or whatever caused this situation to occur. In this view, if the threatened party harms the innocent persons, NAP is not violated. Furthermore, some supporters argue that actions that minimize harm are consistent with NAP.
Other critics state that the NAP is unethical because it does not provide for the violent prohibition of, and thereby supposedly legitimizes, several forms of aggression that do not involve intrusion on property rights, such as verbal sexual harassment, defamation, boycotting, noninvasive striking, and noninvasive discrimination. If a victim thus provoked would turn to physical violence, according to the NAP, he would be labeled an aggressor. Supporters of the NAP, however, state that boycotting and defamation both constitute freedoms of speech and that boycotting, noninvasive striking, and noninvasive discrimination all constitute freedoms of association, and that both freedoms of association and of speech are nonaggressive. Supporters also point out that prohibiting physical retaliation against an action is not itself condonement of said action, and that generally there are other, nonphysical means by which one can combat social ills (e.g., discrimination) that do not violate the NAP. Some supporters also state that while, most of the time, individuals choose voluntarily to engage in situations that may cause some degree of mental battering, this mental battering begins, when it cannot be avoided, to constitute unauthorized physical overload of the senses (i.e., eardrum and retina) and that the NAP, at that point, does apply.
Many supporters consider verbal and written threats of imminent physical violence sufficient justification for a defensive response in a physical manner. Such threats would then constitute a legitimate limit to permissible speech. Because freedom of association entails the right of owners to choose who is permitted to enter or remain on their premises, legitimate property owners may also impose limitation on speech. For example, the owner of a theatre, wishing to avoid a stampede, may prohibit those on her property from calling ‘fire!’ without just cause. The owner of a bank, however, may not prohibit anyone from urging the general public to a bank run, except insofar as this occurs on the property of said owner.
H.L. Mencken, a writer who influenced many libertarians, puts an ethical limit on the freedom of speech:
I believe there is a limit beyond which free speech cannot go, but it's a limit that's very seldom mentioned. It's the point where free speech begins to collide with the right to privacy. I do not think there are any other conditions to free speech. I've got a right to say and believe anything I please, but I have not got a right to press it on anybody else. [...] Nobody's got a right to be a nuisance to his neighbors.
Supporters also consider physical threats of imminent physical violence (e.g., pointing a firearm at innocent people, stocking up nuclear weapons that cannot be used discriminately against specific individual aggressors) sufficient justification for a defensive response in a physical manner. Such threats would then constitute a legitimate limit to permissible action.
Natural resources and environmental pollution
Critics argue it is not possible to uphold NAP when protecting the environment as most pollution can never be traced back to the party that caused it. They therefore claim that only general broad government regulations will be able to protect the environment. Supporters cite the problem of the tragedy of the commons and argue that free-market environmentalism will be much more effective in conserving nature. Political theorist Hillel Steiner emphasizes that all things made come from natural resources and that the validity of any rights to those made things depends on the validity of the rights to the natural resources. If land was stolen then anyone buying produce from that land would not be the legitimate owner of the goods. Also, if natural resources cannot be privately owned but are, and always will be, the property of all of mankind then NAP would be violated if such a resource would be used without everybody’s consent (see the Lockean proviso and free-market anarchism). Libertarian philosopher Roderick Long points out that, as natural resources are required not only for the production of goods but for the production of the human body as well, the very concept of self-ownership can only exist if the land itself is privately owned.
Criticism of NAP as an absolute, rather than relative, concept
Consequentialist libertarian David Friedman, who believes that the NAP should be understood as a relative rather than absolute principle, defends his view by using a Sorites argument. Friedman begins by stating what he considers obvious: A neighbor aiming his flashlight at someone's property is not aggression, or if it is, it is only aggression in a trivial technical sense. However, aiming at the same property with a gigawatt laser is certainly aggression by any reasonable definition. Yet both flashlight and laser shines photons onto the property, so there must be some cutoff point of how many photons one is permitted to shine upon a property before it is considered aggression. But the cutoff point cannot be found by deduction alone, because of the Sorites paradox, so the non-aggression principle is necessarily ambiguous. Friedman points out the difficulty of undertaking any activity that poses a certain amount of risk to third parties (e.g. flying) if the permission of thousands of people that might be affected by the activity is required.
- Long, Roderick (2008). "Nonaggression axiom". In Hamowy, Ronald. The Encyclopedia of Libertarianism. Thousand Oaks, CA: SAGE; Cato Institute. pp. 357–60. doi:10.4135/9781412965811.n219. ISBN 978-1-4129-6580-4. LCCN 2008009151. OCLC 750831024.
...except in response to the initiation ... of similar forcible interference ....
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- Roderick T. Long. "Market Anarchism as Constitutionalism (Anarchism/Minarchism, 2008, Chapter 9)" (PDF). Retrieved 2011-11-16.
- Geoffrey Allen Plauché (Louisiana State University, Baton Rouge, LA). "On the Social Contract and the Persistence of Anarchy (American Political Science Association, 2006)" (PDF). Retrieved 2011-11-16.
- "Review of Kosanke's Instead of Politics – Don Stacy" Libertarian Papers VOL. 3, ART. NO. 3 (2011)
- J. C. Lester. "Why Libertarian Restitution Beats State-Retribution and State-Leniency (2005)". Retrieved 2011-11-12.
- Murray N. Rothbard. "Punishment and Proportionality (The Ethics of Liberty, 1982, Chapter 13)". Retrieved 2011-11-12.
- Philipp Bagus. "Can Dikes Be Private? : An Argument Against Public Goods Theory (Journal of Libertarian Studies, Vol. 20, No. 4, Fall 2006, pp. 21–40)". Retrieved 2011-11-17.
- Walter Block. "The Non-Aggression Axiom of Libertarianism (LewRockwell.com, February 17, 2003)". Retrieved 2011-11-12.
- Phred Barnet. "The Non-Aggression Principle (Americanly Yours, April 14, 2011)". Retrieved 2011-11-22.
- Matt Zwolinski. "Six Reasons Libertarians Should Reject the Non-Aggression Principle". Retrieved 2014-12-01.
- Murray N. Rothbard. "Lifeboat Situations (The Ethics of Liberty, 1982, Chapter 20)". Retrieved 2011-11-15.
- Murray N. Rothbard, "Freedom of Speech," §1 of "Personal Liberty," ch. 6, in "Libertarian Applications to Current Problems," pt. 2 of For a New Liberty: The Libertarian Manifesto (Auburn, AL: Ludwig von Mises Institute, 2006; orig. 1973, 1978), pp. 117–118.
- Murray N. Rothbard, "The Boycott," ch. 18, in "A Theory of Liberty," pt. 2 of The Ethics of Liberty (New York, N. Y.: New York University Press, 1998; orig. 1982), pp. 131–132. Cf., pp. 77, 79, 240.
- Murray N. Rothbard, "Freedom of Speech," §1 of "Personal Liberty," ch. 6, in "Libertarian Applications to Current Problems," pt. 2 of For a New Liberty: The Libertarian Manifesto (Auburn, AL: Ludwig von Mises Institute, 2006; orig. 1973, 1978), pp. 116–117.
- Murray N. Rothbard, "Knowledge, True and False," ch. 16, in "A Theory of Liberty," pt. 2 of The Ethics of Liberty (New York, N. Y.: New York University Press, 1998; orig. 1982), pp. 121–122, 126–128.
- Murray N. Rothbard, "Anti-Strike Laws," §4 of "Involuntary Servitude," ch. 5, in "Libertarian Applications to Current Problems," pt. 2 of For a New Liberty: The Libertarian Manifesto (Auburn, AL: Ludwig von Mises Institute, 2006; orig. 1973, 1978), pp. 102–104. Cf., pp. 93, 118. Cf., The Ethics of Liberty, pp. 77, 132.
- Murray N. Rothbard, "Street Rules," §2 of "The Public Sector, II: Streets and Roads," ch. 11, in "Libertarian Applications to Current Problems," pt. 2 of For a New Liberty: The Libertarian Manifesto (Auburn, AL: Ludwig von Mises Institute, 2006; orig. 1973, 1978), pp. 255–256. Cf., pp. 103, 128.
- Professor Murray N. Rothbard, in "Natural Law and Natural Rights," ch. 4, in "Introduction: Natural Law," pt. 1 of The Ethics of Liberty (New York, N. Y.: New York University Press, 1998; orig. 1982), p. 24, writes:
"Right" has cogently and trenchantly been defined by Professor Sadowsky:
When we say that one has the right to do certain things we mean this and only this, that it would be immoral for another, alone or in combination, to stop him from doing this by the use of physical force or the threat thereof. We do not mean that any use a man makes of his property within the limits set forth is necessarily a moral use?
- Murray N. Rothbard, "Self-Defense," ch. 12, in "A Theory of Liberty," pt. 2 of The Ethics of Liberty (New York, N. Y.: New York University Press, 1998; orig. 1982), pp. 77–78, 80. Cf., For a New Liberty, p. 27.
- Linda & Morris Tannehill, The Market for Liberty (San Francisco: Fox & Wilkes, October 1993; orig. March 1970), pp. 4, 10. Cf., pp. 77, 80
- Murray N. Rothbard, "Property Rights and 'Human Rights'," §5 of "Property and Exchange," ch. 2, in "The Libertarian Creed," pt. 1 of For a New Liberty: The Libertarian Manifesto (Auburn, AL: Ludwig von Mises Institute, 2006; orig. 1973, 1978), pp. 52–53. Cf., pp. 85–86, 115.
- Ben’s Blog. "Fred Phelps, Freedom of Speech and 'the Last Limits of the Endurable' (Ben's Blog on Infinite Monkeys, Fri, 10/08/2010)". Retrieved 2011-11-26.
- Murray N. Rothbard, "Self-Defense," ch. 12, in "A Theory of Liberty," pt. 2 of The Ethics of Liberty (New York, N. Y.: New York University Press, 1998; orig. 1982), pp. 77–78, 80. Cf., pp. 81–82, 189–191, 194.
- Murray N. Rothbard, "The Nonaggression Axiom," §1 of "Property and Exchange," ch. 2, in "The Libertarian Creed," pt. 1 of For a New Liberty: The Libertarian Manifesto (Auburn, AL: Ludwig von Mises Institute, 2006; orig. 1973, 1978), p. 27. Cf., p. 335.
- Murray N. Rothbard. "Law, Property Rights, and Air Pollution (Cato Journal, Vol. 2, No. 1, Spring 1982, pp. 55–99)" (PDF). Retrieved 2011-11-24.
- Graham Dawson. "Free Markets, Property Rights and Climate Change: How To Privatize Climate Policy (Libertarian Papers, Vol. 3, No. 10, 2011, pp. 1–29)" (PDF). Retrieved 2011-12-04.
- Hillel Steiner. "Left-Libertarianism and the Ownership of Natural Resources (Bleeding Heart Libertarians, April 24, 2012)". Retrieved 2012-07-07.
- Eric Mack. "Natural Rights and Natural Stuff (Bleeding Heart Libertarians, April 23, 2012)". Retrieved 2012-07-07.
- Roderick Long. "Self-Ownership and External Property (Bleeding Heart Libertarians, April 25, 2012)". Retrieved 2012-07-07.
- David D. Friedman. "Problems (The Machinery of Freedom, 1989, Chapter 41)". Retrieved 2013-01-03.
- The Non-Aggression Axiom of Libertarianism by Walter Block, LewRockwell.com
- The Philosophy of Liberty, an animated production, derives a libertarian philosophy from the principle of self-ownership. Central to this is the non-aggression principle.
- Antiwar.com is a website devoted to opposing aggressive war, imperialism, and assaults on freedom associated with both. The editors describe their political view as libertarian.
- Zero Aggression Project A website devoted to teaching the concepts of the Zero Aggression Principle with easy to use Heuristics – A project of DownsizeDC.org