Book excerpt: Humans are unique in their ability to create systematic accounts of the world – theories based on guiding cosmological principles. This book is about the role of cognition in creating cosmologies, and explores this through the ethnography and history of Yijing divination in China. Diviners explain the cosmos in terms of a single substance, qi, unfolding across scales of increasing complexity to create natural phenomena and human experience. Combined with an understanding of human cognition, it shows how this conception of scale offers a new way for anthropologists and other social scientists to think about cosmology, comparison and cultural difference.