UNTIL this week America's authorities clung to the hope that they could tide over the financial system with a few loans until home prices stabilised and all the bad debts were accounted for. But the destruction visited on Wall Street in the past week has dashed those aspirations and forced policymakers to consider a more sweeping response. The bankruptcy of Lehman Brothers and AIG’s federal takeover have triggered a wholesale flight to safety that could turn illiquid institutions insolvent. Healthy corporations can no longer issue bonds. Banks can barely borrow from each other.