Anti-Semitism provides a perpetual conundrum for Jews. But the thing that makes it stand out as a challenge for non-Jews is what it says about a society that indulges in it. Because a final aspect of anti-Semitism that is worth dwelling on is what it in fact means. There is enough evidence to say that anti-Semitism does not just pose a challenge to Jews. It also presents a surefire way to diagnose the health of the wider society.