The harm principle holds that the actions of individuals should be limited only to prevent harm to other individuals. John Stuart Mill articulated the principle in the 1859 essay On Liberty, where he argued 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." An equivalent was earlier stated in France's Declaration of the Rights of Man and of the Citizen of 1789 as, "Liberty consists in the freedom to do everything which injures no one else; hence the exercise of the natural rights of each man has no limits except those which assure to the other members of the society the enjoyment of the same rights. These limits can only be determined by law." It finds earlier expression in Thomas Jefferson's 1785 "Notes on the State of Virginia," Query 17 (Religion) in which he writes, "The legitimate powers of government extend to such acts only as are injurious to others."
Definition
The belief "that no one should be forcibly prevented from acting in any way he chooses provided his acts are not invasive of the free acts of others" has become one of the basic principles of libertarian politics.
In R v Malmo-Levine, the Supreme Court of Canada claimed that there was no such thing as the harm principle even though it had been found to be a principle of fundamental justice in the courts below and had been found in all the key documents in the formulation of the concept of justice in Western society, including but not limited to the English and French Constitutions, John Stuart Mill’s On Liberty, and modern case law.
The Harm Principle is found in article 5 of the first English-language constitution from 1647: "An Agreement of the People for a firme and present Peace, upon grounds of common right and freedome....", presented to the Army Council, E. 412, 21. October 28, 1647:
The Harm Principle is found in Articles 4 and 5 of the first French constitution (and first nationally-adopted constitution) from 1789: Declaration of Human and Civic Rights of 26 August 1789:
The harm principle was first fully articulated by the English philosopher John Stuart Mill [JSM] (1806–1873) in the first chapter of On Liberty (1859), where he argued that:
Mill also put the harm principle within his list of rights that sprung from liberty. It was found within his list of political rights (political activities that did not involve harm to others) - but also within his non-political liberty rights - his "tastes and pursuits" - activities which did not involve politics and did not involve harm to others:
One might rightly argue that the "pursuit of Happiness" mentioned in the 1776 US Declaration of Independence was one of the "tastes and pursuits" that Mill had in mind:
The Harm Principle is also found in recent US case law - in the case of the People v Alvarez, from the Supreme Court of California, in May, 2002:
The Harm Principle even found its way into the drug laws of Columbia, in 1994, and again in 2009:
In their decision in R v Malmo-Levine, the Supreme Court did not explain how the Harm Principle was both 1) not a principle of fundamental justice, and 2) found in all these sources of fundamental justice.
Even if a self-regarding action results in harm to oneself, it is still beyond the sphere of justifiable state coercion.
Harm itself is not a non-moral concept. The infliction of harm upon another person is what makes an action wrong.
Harm can also result from a failure to meet an obligation. Morality generates obligations. Duty may be exacted from a person in the same way as a debt, and it is part of the notion of duty that a person may be rightfully compelled to fulfill it.
Restrictions
In On Liberty, J. S. Mill writes that his principle does not apply to persons judged as mentally ill, "barbarians" (which he assimilated to minors) and minors while the Declaration of the Rights of Man and of the Citizen did not concern women, slaves, foreigners and minors, as they were not citizens.
Modern interpretation of the principle often does not make distinction of race or sex.
Broader definitions of harm
In the same essay, Mill further explains the principle as a function of two maxims:
The second of these maxims has become known as the social authority principle.
However, the second maxim also opens the question of broader definitions of harm, up to and including harm to the society. The concept of harm is not limited to harm to another individual but can be harm to individuals plurally, without specific definition of those individuals.