igidity and adaptation, stiffness and flexibility: these are ways we characterize structures in our built environment as well as psychological dispositions. Political institutions and agents also vary along a continuum between the rigid and the adaptable-some may be stiff to the point of brittleness, while others are flexible to the point of fluidity. Somewhere between these poles may lie the right balance of structure and pliability. Machiavelli's prince must have the flexibility to be both a lion and a fox, strong and sly. Modern political institutions that look like rigid hierarchies may contain elements of slack, such as the often extensive discretion possessed by front-line workers in bureaucracies. Other institutions adapt because they are porous, open to reshaping by external ideologies and insurgent actors.When states fail to adapt to new grievances and movements, events such as the Arab Spring may occur, as analyzed by Tansa George Massoud, John Doces, and Christopher Magee in this issue's first article, "The Arab Spring: An Empirical Investigation." 1 Their analysis of protests in nineteen Arab League states in the 1990-2011 period concludes that protests were more intense in partial democracies with factional politics, corruption, repression, inflation, and a high use of the Internet and cell phones, and not due to a demographic youth bulge. In "State Building through Mediation: The U.S. Anti-Submarine Warfare Operations Research Group in World War II," Gerald Berk focuses on what would appear to be a very rigidly hierarchal institution-the U.S. military in wartime-and reveals the surprising degree of creative adaptation on the ground (or rather, at sea), as soldiers and scientists experimented with ways to confront German U-Boat attacks. 2 Next, Inder S. Marwah examines the flexible career of developmentalism. In "Provincial-