Towards the end of his life, I got to know the late Herb Stein, the Chairman of the Council of Economic Advisers under Presidents Nixon and Ford, and I now regret never having asked him for the definitive version of what has come to be known as Herb Stein’s Law. Google tells me that the law is: “If something can’t go on forever, it will stop,” but I like to think that Herb would have preferred what seems to me the more rhetorically satisfying version, whose provenance I cannot now recall: “If something can’t go on forever, it won’t.” Either way, what amounts to a simple tautology has shown again and again its power to strike through the vaporous fogs of public debate to astound us with the force of revelation—although, as I write, it appears not yet to have done so, except in a few odd corners out of the way of the dominant media, in the case of that now legendary precipice, the “fiscal cliff.&rdq ...