Both more and less than what its title promises, Thomas Cahill‘s How the Irish Saved Civilization: The Untold Story of Ireland’s Historic Role From the Fall of Rome to the Rise of Medieval Europe includes among its wide-ranging subjects Plato, Augustine, the fall of Rome, the Gaelic epic Tain Bo Cuailnge, Lindow Man, and St. Patrick—the Romanized British Celt who, after escaping from the Irish raiders who had enslaved him, returned to Ireland to be one of the most successful missionaries in recorded history. It was Patrick who led Ireland to Christianity just as Rome was collapsing, thus ensuring (in the words of Kenneth Clark) that “for quite a long time—almost a hundred years—western Christianity survived by clinging to places like Skellig Michael, a pinnacle of rock 18 miles from the Irish coast.” Cahill discusses his book at 7 p.m. at Olsson’s, 1200 F St. NW. FREE. (202) 347-3686; at 8 p.m. tomorrow at the S. Dillon Ripley Center Lecture Hall, 1100 Jefferson Dr. SW. $15. (202) 357-3030. (MJ)