THE historian Walter Russell Mead recently noted that after the 1990s revolution that collapsed the Soviet Union, Russians had a saying that seems particularly apt today: “It’s easier to turn an aquarium into fish soup than to turn fish soup into an aquarium.” Indeed, from Europe to the Middle East, and maybe soon even to Russia and Asia, a lot of aquariums are being turned into fish soup all at once. But turning them back into stable societies and communities will be one of the great challenges of our time.