An introduction to a vast but uncompleted survey of world history, this article argues that the study of the changing relationships among cities, states and trust networks can help us understand key elements of the emergence of our modern world. Beginning in ancient Uruk in modern-day Iraq, roughly five thousand years ago, the essay defines each of its central categories: city, state and trust network. It poses four questions to be pursued throughout the rest of the study. What determines the degree of segregation or integration of cities and states? What determines the relative dominance of cities and states? What determines the extent of separation or integration between cities or states, on one side, and trust networks on the other? What difference do these variable configurations make to the quality of ordinary people’s lives?