Contemporary persons are daily confronted with enormous quantities of information, some of which reveal causal connections between their actions and harm that is visited upon distant others. Given their limited cognitive and information processing capacities, persons cannot reasonably be expected to respond to every cry for help or call to action, but neither can they defensibly refuse to hear and reflect upon any of them. Persons have a limited obligation to know, I argue, which requires that they inform themselves and others about their role in harmful social practices, with a view toward challenging the norms that sustain such practices. In this paper, I explore this obligation to know, and the related idea of excusable ignorance, offering accounts of the epistemic burden that it entails for persons in their capacities as citizens and in the context of global climate change and of reproach as a potentially effective tool for rectifying rather than excusing ignorance. © 2015, Springer Science+Business Media Dordrecht.