QuestionsWhat is a just society?Force may be used only to prevent harm to others
What is a just society?Liberties

Force may be used only to prevent harm to others

The harm principle

John Stuart Mill 1806 · 1873An action is right if it increases happiness, but not all pleasures are equal.
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What it claims

The only legitimate reason to use force against a member of society is to prevent harm to others. His own good, physical or moral, is not a sufficient reason.

Why

When society imposes its way of life on a minority, it is as likely to be wrong as right.

The same idea through history
John Locke1689Locke limits the state's power to civil goods (life, liberty, property) and denies it the care of souls. Mill extends this limit to the whole private life, not just religion.Benjamin Constant1819Constant defends the peaceful enjoyment of private independence as the liberty of the Moderns. Mill turns it into a precise principle saying where the power of society stops.
John Stuart Mill1859In chapter I of On Liberty, Mill states the principle, then defends it in the following chapters (freedom of thought, individuality, limits of the authority of society).
John Stuart Mill1861Mill does not found liberty on an abstract right, but on utility "in the largest sense": it is the same Mill and the same utilitarianism as in his theory of higher pleasures.
In short

"Force may be used only to prevent harm to others" is an argument by John Stuart Mill (On Liberty, 1859, chap. I and IV, 1859) on the question "What is a just society?" (answer: liberties). Its claim: The only legitimate reason to use force against a member of society is to prevent harm to others. His own good, physical or moral, is not a sufficient reason. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P4). AskPhilosophy presents 4 objections, 3 of them with a documented reply, and the original text behind each premise, checked word for word.

On Liberty, 1859, chap. I and IV
Valid with an implicit premise

Should we stop someone from harming himself? Ban drugs, make seat belts compulsory, punish what the majority judges immoral? In On Liberty (1859), John Stuart Mill answers with a simple rule. Society may compel an adult in only one case: to prevent him from harming others. His own good, physical or moral, is not a sufficient reason. One may talk to him, reason with him, plead with him, but not force him. Mill does not rest this rule on an abstract right but on the utility of all. The principle has become the reference point of debates on individual liberty.

P1The ultimate standard in ethics is utility, understood in the largest sense: grounded on the permanent interests of man as a progressive being.
P2When society imposes on a minority its view of how to conduct one's personal life, it is as likely to be wrong as right: public opinion there is, at best, some people's opinion of what is good for others.
P3So, in the name of utility, external compulsion is authorised only for acts that concern the interests of other people.
P4 · implicit premiseA person's own good (health, virtue, happiness) belongs to the part of his conduct that concerns only himself.
Therefore the only legitimate reason to use force against a member of society is to prevent harm to others. His own good, physical or moral, is not a sufficient reason.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P4, the computer finds a world where compulsion is authorised only for acts that concern others, but where a person's own good counts among those acts (because his health or virtue concerns the whole society): he could then legitimately be compelled for his own good.
Valid with P4. P1 to P3 give: we may compel only for acts that concern others. To conclude that a person's own good is not a reason, we need P4: the individual alone is concerned by his own good. Mill writes it ("over himself, over his own body and mind, the individual is sovereign"), but this is exactly the point critics attack: does what I do to myself never fall back on others? Note also step P2: Mill does not prove that the state is always wrong, only that it is as often wrong as right in this domain.
Analogy. Think of your phone. Your parents may tell you you use it too much, show you figures, plead with you to stop. Mill says that is fine. But if they confiscate it for your own good, they cross the line. They would be entitled to step in if you used it to harass someone.

Objections

4

Each objection is a conversation: click to see who replies and where the debate stands.

James Fitzjames Stephen 1873 · attacks premise 3

Mill states his principle but hardly proves it: the following chapters repeat it more than they argue for it. A principle this important needs to be demonstrated, and Stephen holds that it is not.

no reply
No reply possible: objection raised in 1873, after the author's death (1873).
Where the debate stands (our summary)Stephen grants that chapters II to IV may be read as proofs of separate parts of the principle (free discussion is good, individuality is an element of well-being), but not of the whole principle. The disagreement is about what counts as proof in ethics. Our summary.
James Fitzjames Stephen 1873 · attacks the conclusion

Mill accepts that the disapproval of others weighs on those who behave badly. Why then would it always be wrong to punish drunkenness with a fine, and always right to punish it with contempt? Stephen cannot see what the difference rests on: in both cases society makes someone suffer because it disapproves of his conduct.

Mill replies
Mill What Mill writes (he does not answer Stephen, but he draws this distinction)
Mill holds that the only inconveniences one should suffer for the part of one's conduct that concerns only oneself are those strictly inseparable from the unfavourable judgment of others. Acts injurious to others require a totally different treatment.
Where the debate stands (our summary)Stephen asks for a difference of principle between social and legal sanction; Mill places it in the spontaneous character of others' reactions, as opposed to organised punishment. The basic disagreement is whether this line is sharp enough to carry the whole principle. Our summary.
P
Patrick Devlin 1959 · attacks the conclusion

A society is held together by a shared morality, as it is by a government. If acts that almost everyone judges immoral spread, society risks coming apart, as under the effect of treason. It is therefore entitled to use the law to defend itself against immorality as such, even when nobody is directly harmed.

a defender replies
No reply possible: objection raised in 1959, after the author's death (1873).
H
H. L. A. Hart defender of the argument · 1963
Summary: Hart argues that Devlin offers no evidence that departing from the common morality destroys a society. He distinguishes the existence of a shared morality, which is necessary, from its precise content, which changes without society disappearing. He keeps Mill's principle: immorality alone is not a reason to punish.
Where the debate stands (our summary)The basic disagreement is both factual and moral: can a society survive a change in its customs (Hart: yes, it changes) or does it threaten it (Devlin: yes, like treason)? And does common indignation suffice to justify a law? Our summary.
B
Bernard E. Harcourt 1999 · attacks premise 4

The word "harm" draws no clear border. Each side claims that what it fights harms someone: pornography, drugs, what some call immoral. Once anything can be described as a harm, the principle settles nothing; it serves both sides.

Mill replies
John Stuart Mill What Mill writes (long before the objection)
Mill answers in advance by distinguishing real injury from mere disgust: the feeling of one person shocked by another's belief has nothing to do with the damage suffered by someone whose purse is taken. He also sets a limit for relatives: harm counts when a distinct obligation to someone is breached, not for the mere sorrow his conduct causes.
J
Joel Feinberg 1984
Summary: Feinberg refines the principle. To harm is to set back a person's interests in a way that violates his rights. He treats offence (what shocks or disgusts) separately: it may, in some cases, justify a limit, but it is a principle distinct from harm.
Where the debate stands (our summary)Defenders of the principle (Feinberg) give a more precise definition of harm and separate offence; Harcourt judges that these definitions are themselves disputed and do not settle hard cases. The basic disagreement is whether the principle can exist without a moral theory of harm. Our summary.
What today's voices say
Defend it
Martha NussbaumShe argues that the harm principle is the proper limit on individual liberty, and that law should not rest on disgust or shame.