Why study history?

The question "Why study history?" finds a ready answer on an almost daily basis on Jerry Pournelle's site. An example, built from one of the most fascinating periods of European history, the Thirty Years War: "... the world is in much the same condition now as it was during the Thirty Years War. Calvinists in that time used the notion of Sovereignty to imprison or execute people like Grotius who believed in free expression. Sovereignty allowed repressive regimes, and gave them a legal status, which both Catholics and Protestants were quick to make use of. The year 1648 is one of those dates to remember: not only did the Treaty of Westphalia change Europe forever (one of Hitler's avowed goals was to reverse that treaty) but the English killed their king and brought in Puritan rule to abolish Christmas and make Merrie England somber and pure. (Charles I was executed in January of what we now consider the year 1649, but in those times the year did not end on 31 December). The world is now larger than Europe, and the United Nations isn't united as the Papacy had been. There is no universal agreement on anything including the status of women. The United States has explicitly repudiated the notion of sovereignty as regards nations that sponsor terrorism and harbor terrorist enemies of the West. The United Nations doesn't recognize that right." Just read the whole thing. Besides evoking Gustavus Adolphus, one of the most fascinating and frustrating, truly pivotal persons of European history—and a good argument for the "great man" view of history, too—the model Pournelle extracts and applies to current events is provocative at the very least.