According to J. S. Mill’s liberty principle, the only legitimate justification for restricting the freedom of competent adults is to prevent harm to others. However, this is ambiguous between two interpretations. The harm causation version (Brown, 1972) has it that only conduct that is itself harmful is liable to interference. In contrast, the general prevention of harm version (Lyons, 1979) allows interference with conduct that does not itself cause harm, such as refusals to assist others, so long as this interference prevents harm from occurring.
Mark Tunick (2024) has recently offered new arguments for the harm causation interpretation, suggesting that only this can explain Mill’s resistance to legal interference with prostitutes. This paper challenges Tunick’s arguments. First, I show that Mill does not clearly restrict interference to the proximate causes of harm. While he prefers interference to focus on the clients, rather than singling out the prostitutes, he is prepared to countenance interference with the prostitutes as well. Further, his preference for focusing on the clients is explicable, even if not required by the liberty principle.