With the publication of the final report of the WHO Commission on the Social Determinants of Health, it becomes clear that there is considerable convergence between a policy agenda rooted on social epidemiology and one rooted in a concern for human rights. As commentators like Jonathan Mann have argued, concern for human rights and the achievement of social justice can inform and improve public health. In this article, we ask a different question: what does a health perspective adds to the enduring fight for a more just world? We consider three possibilities: (1) that public health, in an inversion of Mann's argument, actually provides useful tools for specifying social injustice; (2) that, contrary to the usual critical stance and assumption of weakness, the institutions of public health bring powerful capacities to the practical promotion of social justice; and (3) that health as a banner mobilizes people who would not be mobilized to act in the name of social justice.