A standard worry about Hume’s account of justice is that it leaves those who are most vulnerable outside the circumstances of justice. An equally standard reply is that those who are so vulnerable as to fall outside the scope of justice need not thereby fall outside the scope of morality altogether, because on Hume’s account we will often have duties of humanity to treat vulnerable creatures decently. It is not clear that this reply is adequate, for given the apparent priority of justice over natural virtues like those of humanity, it is not clear that duties of humanity provide enough protection for the weak. This paper identifies another problem with Hume’s reply: if those who are extremely vulnerable are nonetheless rational and fully capable of autonomous judgment about how to live, then Hume’s theory still delivers the wrong sorts of protections for them. In particular, it is very plausible to suppose that it would be immoral to engage in paternalistic interference with the decisions of such weak but rational agents about how to live, as long as they are not thereby harming or wronging anyone else. Treating such rational but vulnerable agents paternalistically seems unjust, but Hume’s account cannot vindicate this intuition. Indeed, Hume not only cannot explain why such paternalism is unjust, he seems forced to conclude that we will often be obligated by duties of humanity to engage in such paternalism. For Hume seems committed to the unpalatable conclusion that morality speaks unambiguously in favour of paternalistic interference in such cases as long as we can be reasonably sure that the intended beneficiaries really will be made better off. In this paper, I develop and press this new objection from paternalism against Hume’s account of the circumstances of justice.