Persson and Savulescu are advocates for moral bioenhancement—i.e., using drug treatments and genetic engineering to enhance our core moral dispositions. Among other things, they suggest that moral bioenhancement would improve how we treat animals. My goal here is to argue that we have little reason to think that moral bioenhancement will help in this regard. What’s more, it may make things worse. This is because there are cognitive mechanisms that lead us to discount animal interests relative to human interests—mechanisms not (...) overridden by increased altruism and a stronger sense of justice—and there are deep tensions between the interests of humans and animals that moral bioenhancement may well exacerbate. (shrink)