FOR reasons that need, sadly, no explanation, we find ourselves living in a nervous, uneasy era, a time when every backfiring car becomes a bomb, every spilled sachet of sugar a plague. Once again, an enemy is out there, but the threat now is not the familiar Soviet-style Armageddon, but the occasional hit-and-run, jihad on the installment plan, which although revoltingly vicious, should, with luck— and preparation—leave most of us unscathed. Preparation? Back in the Cold War years, that never seemed necessary. Mutually Assured Destruction meant that the threat to civilians was both minimal and total. Now attacks seem certain, [...]