Whenever advocates work to spare the lives of animals, there are invariably those who criticize them by arguing that animals are less important than people and we should ignore one in deference to the other. It is a tragically commonplace argument, but no less indefensible because of it. In effect, they are arguing that compassion is zero-sum, that it ought to be doled out in a miserly fashion, and that unless and until we end all human suffering, we should ignore the harm to every other earthling who shares our planet —