Introductory

Mill opens by tracing the oldest theme in history: the struggle between liberty and authority. But its form has changed. Where once the fight was against rulers imposed from above, in a self-governing society the danger shifts — the people may oppress a part of themselves, and opinion may coerce more deeply than law. Borrowing the phrase from Tocqueville, he names this the tyranny of the majority, and insists it deserves as much vigilance as any exercise of formal power.

Against this pressure he sets the harm principle: the only legitimate ground for compulsion is the prevention of harm to others. A person's own good — bodily or mental — does not justify coercion. He may be argued with, entreated, or avoided; he may not be forced. Within the sphere of self-regarding conduct, society has no rightful authority, however strongly it disapproves of what it finds there.

Mill then marks out the inner sphere that the book will defend: liberty of conscience, of thought and expression, of tastes and pursuits, and of voluntary association among consenting adults. These, he argues, are the conditions under which character forms and self-determination is possible. Any society that invades them — even with the best intentions — diminishes the very persons it claims to be protecting.