[Protecting vulnerable persons: an ethical requirement in need of clarification]

Protecting vulnerable persons is important. But who is vulnerable and what protections are required? This article outlines versions of vulnerability found in the literature: vulnerability as human finitude, as a lesser ability to protect one's interests, as fragility, as a hindrance to health. It then proposes a definition of vulnerability as an increased risk of incurring a wrong and examines how this definition could be applied to clear-cut as well as controversial cases of vulnerability. Protecting vulnerable persons requires a diagnostic approach: identifying the wrong involved, the source of vulnerability, adequate protections, as well as the persons who participate in the duty of protection.