The exception that proves the rule

I first learned a more useful meaning of the expression "the exception that proves the rule" from the essay "Death Before Birth, or a Mite's Nunc Dimittis " in The Panda's Thumb , a 1980 collection by paleontologist Stephen Jay Gould. (I would link to the full version of the essay, but it seems the only website freely hosting it is an archive dedicated to Ted Kaczynski , so, uh, yeah.) In common…