Behind his white beard, Federal Reserve chairman Ben Bernanke has a wry sense of humour. On reading his recent speech to the American Economic Association, in which he defended the Fed's actions during the housing bubble, I initially suspected it was a practical joke. Rather than conceding that he and his predecessor, Alan Greenspan, made a hash of things between 2002 and 2006, keeping interest rates too low for too long, he said the Fed's policies were reasonable and the main cause of the rise in house prices was not cheap money but lax supervision.

Searching in vain for a punch line, I was reminded of Talleyrand's quip about the restored Bourbon monarchs: “They have learned nothing and forgotten nothing.” Mr Bernanke is far smarter than Louis XVIII and Charles X, two notorious boneheads, and has done a good job of firefighting. But his unwillingness to admit the Fed's role in inflating the housing and broader credit bubble raises serious questions about his judgment.

The individual elements of his presentation were questionable enough – is it really plausible to suggest that record low mortgage rates did not contribute much to the rise in US house prices? – but most disturbing was its failure to address the larger picture: from the mid-1990s, the Fed adopted a stance that encouraged irresponsible risk-taking. In periods of growth, it raised interest rates slowly, if at all, stubbornly refusing to acknowledge the course of asset prices. But when a recession or financial blow-up beckoned, it slashed rates and acted as a lender of last resort.