The study unearths in European writings about chief rivals -- Islamic civilization between the first Crusade in 1095 and the final Ottoman siege of Vienna in 1683, and the United States of America from independence in 1776 until the present - persistent solicitude regarding Europe's capacity to lead the world. Intriguingly, however, this very self-doubt prompted the kind of intense introspection which helped, in the past, to forge seismic progressive...