The harm threshold and Mill's harm principle

The Harm Threshold (HT) holds that the state may interfere in medical decisions parents make on their children's behalf only when those decisions are likely to cause serious harm to the child. Such a high bar for intervention seems incompatible with both parental obligations and the state's role in protecting children's well-being. In this paper, I assess the theoretical underpinnings for the HT, focusing on John Stuart Mill's Harm Principle as its most plausible conceptual foundation. I offer (i) a novel, text-based argument showing that Mill's Harm Principle does not give justificatory force to the HT; and (ii) a positive account of some considerations which, beyond significant harm, would comprise an intervention principle normatively grounded in Mill's ethical theory. I find that substantive recommendations derived from Mill's socio-political texts are less laissez-faire than they have been interpreted by HT proponents. Justification for state intervention owes not to the severity of a harm, but to whether that harm arises from the failure to satisfy one's duty. Thus, a pediatric intervention principle derived from Mill ought not to be oriented around the degree of harm caused by a parent's healthcare decision, but rather, the kind of harm-specifically, whether the harm arises from violation of parental obligation. These findings challenge the interpretation of Mill adopted by HT proponents, eliminating a critical source of justification for a protected domain of parental liberty and reorienting the debate to focus on parental duties.