This is an open access title available under the terms of a CC BY-NC-ND 4.0 International licence. It is free to read at Oxford Scholarship Online and offered as a free PDF download from OUP and selected open access locations. Very often we're uncertain about what we ought, morally, to do. We don't know how to weigh the interests of animals against humans, how strong our duties are to improve the lives of distant strangers, or how to think...