Struggles over drinking water, new outbreaks of mass violence, ethnic cleansing, civil wars in the earth's poorest countries, endless flows of refugees: these are the new conflicts and forces shaping the world of the 21st century. They no longer hinge on ideological rivalries between great powers but rather on issues of class, religion and resources. The genocides of the last century have taught us how quickly social problems can spill over into radical and deadly solutions. Rich countries are...