 Here, the Xici authors link the popularity of hexagram divination to the momentous transition when the mandate of heaven (tianming)—the power to rule China—was abruptly passed from the Shang family to the Zhou family. To highlight the importance of divination in assuaging human fear, the Xici authors coin two terms—fear (you) and anxiety (huan)—to describe the different states of human apprehension of uncertainty. To further clarify what fear and anxiety mean, the Xici authors write: