Bugbears for each generation
A hundred years ago, the evil menacing people purported to lurk in every shadow were anarchists. By the 1920s, and continuing of course through the 1950s and beyond, the Communists took over as Chief Bugaboo of the American imagination. (What ever happened to the anarchists as objects of fear, anyway? Were they just eclipsed by the Red Menace? I'm guessing Nick will be able to tell us. And who was it before the anarchists?) And now we've got terrorists. Each time around, some of the same things happen—taking away of civil liberties, mass panic, worries that civilization will fall to The Lurking Enemy. On the one hand, we seem to eventually get over it each time; on the other hand, it takes longer than would be ideal.
Thoughts sparked by this 2003 Swarthmore commencement speech from Jed S. Rakoff '64 (one of a distinguished line of Jeds who have attended Swat; I think there've been five or six of us). Thanks to Joe and (obliquely) Fred for pointing to that.