Diamond, like Singer and Regan, wants to argue for vegetarianism. She notes that the arguments of Singer and Regan focus on the interests and capacities of individual animals as a basis for why we should not eat meat. For Singer, eating meat is wrong because it contributes to the pain of animals. For Regan, it is this capacity to experience pain that is the basis of animal rights. Diamond says that such arguments are failing to recognize the significant issue. Such arguments usually rely on some sort of analogy between animals and non-rational human beings. E.g., because animals and non-rational humans are both capable of experiencing pain, it is wrong to eat both animals and non-rational humans. This is not the relevant analogy, Diamond says.
The proper analogy is not to talk about eating animals and people but to talk about the death rituals for animals and people. Diamond says that the reason why we don't eat dead people is because humans are not the kind of thing to be eaten. Our concept of what counts as a kind of thing to be eaten changes over time. We tend not to eat or treat badly entities that we consider to be 'fellow creatures'. Humans, Diamond says, are the kind of things that we honor in death with ceremony; they are also the kind of things to be named rather than numbered. Clearly there are many examples where humans have numbered other humans or where humans have been disrespectful towards other humans in life and in death. Again, the notion about who we count as a 'fellow' creature or 'fellow' human changes over time. Diamond says that we should extend the notion of fellow creature to non-human animals.