J.S. Mill argues against licensing or forced medical examinations of prostitutes even if these would reduce harm, for two reasons: the state should not legitimize immoral conduct; and coercing prostitutes would violate Mill's harm principle as they do not risk causing non-consensual harm to others, their clients do. There is nothing puzzling about Mill opposing coercive restrictions on self-regarding immoral conduct while also opposing state support of that conduct. But why does Mill oppose restrictions on prostitutes’ liberty if those restrictions could prevent harm to third parties? Mill's position is not puzzling once we recognize that his harm principle is not a harm-prevention principle that warrants restrictions on liberty to prevent harm no matter who caused it (as David Lyons famously argued) but instead warrants restrictions on liberty only of individuals who are the morally relevant cause of that harm. Mill's discussion of prostitution shows he prioritizes both individuality and moral progress over harm reduction.

J.S.米尔反对对妓女进行许可或强制体检，即使这会减少伤害，原因有两个：国家不应该使不道德行为合法化；强迫妓女将违反米尔的伤害原则，因为他们不会冒对他人造成非自愿伤害的风险，但他们的客户却会这样做。穆勒反对对利己的不道德行为进行强制限制，同时也反对国家支持这种行为，这并不令人费解。但如果这些限制可以防止对第三方的伤害，穆勒为什么反对限制妓女的自由呢？一旦我们认识到穆勒的伤害原则不是一种伤害预防原则，即保证限制自由以防止伤害，无论伤害是谁造成的（正如大卫·莱昂斯著名的主张），米尔的立场就不再令人费解了，而是只保证限制那些受到伤害的个人的自由。该伤害的道德相关原因。密尔对卖淫的讨论表明，他将个性和道德进步置于减少伤害之上。