TÜBINGEN, Germany, April 23 - For all Pope Benedict XVI's decades as a Vatican insider, it may have been the crucible of a university town swept by student radicalism in the late 1960's that definitively shaped the man who now leads the Roman Catholic Church. During his Bavarian childhood under the Nazis, Joseph Ratzinger became convinced that the moral authority based in Catholic teachings was the sole reliable bulwark against human barbarism, according to friends, associates, and his biographer, John L. Allen Jr. But while his deep reading and thinking in theology, philosophy, and history were fundamental to development as...