Economics of Hereness examines the east-central European origins of development concepts that came to dominate the postwar world. It treats social science as a situated phenomenon, shaped by the twentieth century’s violent politics, and explains why and how developmental thought became the key instrument of defining, building and contesting new nation-states in Europe after World War I—and then globally after World War II. The book reconstructs how Polish economists––mostly Jewish––converted Poland’s intermediary position between the industrialized West and the “underdeveloped” colonial territories into an epistemic advantage. Dubbed “Polish Keynesians,” these activist scholars developed a way of a transforming a small, poor, multiethnic state into a self-expanding economy, and thus an ethnically inclusive polity. They acted against the trend of separating nationalities and ethnic groups in new states with large minority populations. Economics of Hereness recasts the genealogy of development theory from the perspective of the blood-and-guts history of Poland and east-central Europe.