A timely look at nationalism, a phenomenon more often noted than analyzed, by Pfaff (Barbarian Sentiments, 1989, etc.), longtime political commentator for The New Yorker, The International Herald Tribune, and The Los Angeles Times. Pfaff believes that nationalism has been the most powerful force of the 20th century--and that it will probably remain so in the 21st. In his judgment, nationalism destroyed Nazism and Communism, as well as imperialism and the colonial system. Yet nationalism is a comparatively modern phenomenon; the original nations were dynastic, with no ethnic base. Indeed, Pfaff points out, the process by which nations have evolved appears almost accidental, and, while nationalism now seems almost a primordial force, it was in fact the product of the European Romanticism of the 19th century. Surprisingly, the author sees little nationalism in the conventional political sense at work in Asia, Africa, or the Middle East. In Asia, it's the continuity of non-Western civilization that dominates, while in Africa, local and tribal loyalty holds sway. Meanwhile, the nations of the Middle East lack historical roots, and Islamic fundamentalism has triumphed, at least in part, because of the very failure of secular nationalism. Pfaff sees a threat in such fundamentalism, though he does not see it as expansionist; but he's most concerned about the failure of the European Community to deal with the ethnic nationalism manifesting in the former Yugoslavia. The author regards the bloody combat there as a crucial blow to the ideals and accomplishments of liberal internationalism, including the UN. Throughout, Pfaff is persuasive, with the lone and curious exception of his consideration of the US itself--where, he says, the South has ``now mostly gone Snopes, to beer and a money-making vulgar patriotism.'' Urbane and intelligent: a useful analysis of a rapidly changing phenomenon.