I’ve just returned from a vacation in Paris, which I report partly to induce envy (I went), partly to seek sympathy (I returned) and primarily—having favorably compared our revolution to theirs in this space—to give credit where due: The French have managed to maintain security amid an environment of openness in a way that has eluded us. Part of the reason is that the French internal security services keep a close watch on radical Islamic activity. Another is that they have not had to confront a calamity on the scale of 9/11. But one wonders, as I have speculated here before, whether some of the difference has to do with attitudes toward risk. The French may have accepted 99 percent security. We demand the full 100. And that extra percentage point—which is, not incidentally, delusive—is a costly one indeed.