A negative and hostile attitude to Jews and the Jewish religion. As a migrant people, the Jews have experienced anti-Semitism within many societies and throughout much of recorded history. The most extreme expression of anti-Semitism was the Holocaust, when six million Jews were murdered in German concentration camps during World War II. This mass killing, carried out in an advanced and intellectually sophisticated society, traumatised Western societies and called into question the then dominant idea that historical development was marked by an increasingly rational commitment to the creation of an enlightened, progressive and humane society.