This article analyzes structure and function in the network design of historical regimes of China and Western Europe to build a theory for the development of societies and states from endogenous mechanisms of social change. It shows how their respective network structures evolved independently but share a global property: both are small worlds, meaning that any node in the network can reach any other node by a small number of steps. Probing the variations in network topologies and their role in diffusion and scaling, the author accounts for differences in formal institutions, interpersonal trust, cultural norms, and moral protocols. Network structure as an independent variable moves the discussion of the divergence of East and West beyond the conventional, centralized China versus decentralized Europe debate. It allows us to identify an overlooked driver of structural change in the polity, helping to discern better what sets the development of world civilizations apart.