Can Christian sin-talk be retrieved within the public sphere? In this contribution to ecotheology, Ernst M. Conradie argues that, amid ecological destruction, discourse on sin can contribute to a multidisciplinary depth diagnosis of what has gone wrong in the world. He confronts some major obstacles related to the plausibility of sin-talk in conversation with evolutionary biology, the cognitive sciences, and animal ethology. He defends an Augustinian insistence that social evil, rather than natural evil, is our primary predicament. If the root cause of social evil is sin, then a Christian confession of sin may yet yield good news for the whole earth.