The chapter opens on the roof of a building, where the two men meet face to face for the first time. The two men discuss the possibility of a fight between the two, but they are interrupted by the sound of a child's voice. The narrator explains that it is not unusual for humans to sacrifice themselves in order to help others, but that this sacrifice is not exclusive to humans. He also explains that the killing of humans is one of the most common forms of animal self-sacrifice, and that this is why it is so popular among scientists and philosophers. He explains that killing children is the most important aspect of this phenomenon, as it also explains the formation of families, the mating of animals for life, and protection of children.