The major themes of Nation by Terry Pratchett include cultural interactions, the role of myth in shaping society, the nature of leadership, and the question of conflict resolution. In many ways, Nation is an updated version of Robinson Crusoe, but one which invokes a universe in which the "primitive" beliefs about the gods turn out to be true, and in which the gods affect the outcomes of human life. One major religious theme is the responsibility of humans to perfect themselves  in their own contexts -- thus Daphne and Mau, rather than becoming a typical romantic couple, go on to become leaders of their respective nations.