On LibertyJohn Stuart Mill

Mill's On Liberty has a single thesis: the only legitimate reason for society to coerce an individual is to prevent harm to others. A person's own good, whether physical or moral, is not sufficient warrant. This "harm principle" is the spine of the book, and everything else serves it.

Chapter II defends freedom of thought and expression with arguments that have never been surpassed in force. Silencing an opinion assumes infallibility. If the opinion is true, we lose the truth. If it is false, we lose the living comprehension that comes from having to defend the truth against challenge. If partly true (as most opinions are), we lose the portion of truth it contains. Even a wholly false opinion keeps received doctrine from hardening into dead dogma.

Chapter III extends the argument to individuality of action. Experiments in living are the source of social progress. Custom, left unchallenged, calcifies into tyranny, and the pressure of mass opinion can be as oppressive as any law. Mill worries specifically about democratic societies, where the majority's moral sentiments tend to enforce conformity without anyone issuing an explicit command.

Chapter IV draws the line between self-regarding and other-regarding conduct, and Chapter V applies the principle to concrete cases: trade regulation, education, marriage, public decency. Mill concedes that the boundary is never perfectly clean, but he insists that the burden of justification always falls on the one who would restrict liberty.