"If economic theory is worth anything at all, it should illuminate economic history. The most usual attempts to interpret history in terms of mainstream economic theory have tended to leave out the specifics and, in particular, the influence of past events and structures on later ones. Avner Greif's work demonstrates the power of using economic theory, especially game theory, to illuminate both structural patterns and change, while still respecting historical specificity. The evolution of medieval trade is used as a case to show how the problems raised by economic theorists (e.g., the need for enforcement of contracts ) are resolved by the creation of institutions which are constrained to be self-enforcing equilibria. I believe Greif's approach will lead to a revolution in the study of other eras and even the changes in present regimes." -Kenneth Arrow, 1972 Nobel Laureate in Economics, and Professor Emeritus, Stanford University.