The fundamental lesson that all people are equal is a child's lesson. By nature, it is something that children learn in school. It has a tendency to disappear as life continues, but its childlike innocence reminds us of how far we have strayed from where we were as children.
In using Bruno as a constant reminder of this lesson, Boyne is able to teach through the novel. Bruno never really loses his perspective, taking it with him to his eventual death. In a world where so much is contingent and so many ideals are abdicated, Boyne shows Bruno never abandoning his ethical positions. In dying for the belief that "all people are equal," Boyne is able to emphasize that adults must possess some level of childlike wonder, like Bruno, that is willing to transform what is into what can be. The child's perspective is a telling reminder that some of the lessons we learn in childhood are the ones that must continue throughout our lives in order to make the world better than when we found it.