Striving so mightily to make one and one add up to three or four or five, Wall Street, Main Street and Washington collectively brought us to the impasse of 2008, in which a debt crisis is superimposed on a downturn in the economy, which is overlaid on a bear market in real estate, which is conjoined with a persistent and worrying weakness in the overseas value of the dollar. As for the crackup in complex mortgage-backed securities, now at the center of the debt predicament, the global bank UBS has justly called it “the biggest failure of ratings and risk management ever.”