Humans use natural and supernatural explanations for phenomena such as illness, death, and human origins. These explanations are available not just to different individuals within a society, but to the same individual, coexisting within a single mind. This chapter proposes that understanding the coexistence of qualitatively different explanations is fundamentally a cognitive–developmental endeavor, speaking to general questions of knowledge acquisition, socialization, and the interaction of cognition and culture. The chapter first reviews research demonstrating that coexistence of natural and supernatural explanations is not a short-lived, transitional phenomenon that wanes in the course of development, but is instead evident (and widespread) among adults. It then speculates on the psychological origins of coexistence and discusses implications for metacognition. Finally, directions are proposed for future research to inform understanding of how individuals incorporate natural and supernatural explanations across content domains, development, and cultures.