AP Photo

While slouching against a wall in a former cigarette factory in the industrial outskirts of The Hague one day last month, I was visited with the sudden realization that over the formative centuries of European history the two words that most succinctly signaled “other,” “foreign” or “enemy” were these: “Jew” and “Turk.” Crudely unpacking them, “Turk” meant Muslim, Arab, infidel, the threat from without; a Jew was the enemy within, someone who, even if born and raised in your hometown, was part of another political as well as religious entity; the Jews of a city were referred to not as a community but as “the Jewish nation.” “Jew” and “Turk” were in fact constructs...