Amerindian myths dealing with the related themes of incest, eclipse, and the origin of the moon's spots reveal glimpses of an elaborate cosmological system, widespread across the Americas, that presents nature in terms of darkness, chaos, corruption, and mortality—in opposition to culture, which is identified with light, order, immortality, and the sacred. This opposition takes diverse manifestations and the mediation of these opposites is achieved, in both myth and ritual, in complex ways. This article uses a comparative approach to analyze myths and motifs documented by Claude Lévi-Strauss. The notorious abuse of comparative mythology in the past to vindicate colonialist and racist agendas has cast a dark shadow over this discipline. Instead of reducing the material to generalized functions of the mind or of human society, the ideas expressed are treated as manifestations of an intellectual tradition. Starting with the structural links that Lévi-Strauss makes between a large body of Amerindian myths, this article will reveal the richness and intellectual depth with which the relevant mythic ideas are elaborated in different cultures. The variations of an idea or motif are approached with the understanding that they are manifestations of a dynamic process of tradition and creation.