How will history judge the Almost-Depression of 07-09?

In 20 years time, the concensus amongst economic historians will be that the prime reason behind the Almost-Depression was central bankers' reluctance to pursue aggressive enough monetary policy, either by generating some inflation so that real interest rates can come down, or by other means.

They will argue that a few percentage points additional inflation would have worked wonders in softening the recession, and they will dismiss arguments that long-term central bank credibility would have suffered as a result. They will marvel at how anyone could have let below target inflation (let alone deflation) take hold, and they will label as disingenuous claims that the tools available to central bankers and policy makers at the time were insufficient to generate the required degree of inflation at will.

They will comment extensively on the shocking lack of international co-ordination, both amongst central banks and governments. Finally, they will have some rude things to say about using fiscal policy, with all its adverse effects on public finances, when a small tax on monetary assets (i.e. inflation) could have done a better job, and much more neatly.

In other words, the consensus in 20 years' time will be what Scott Sumner is already saying today.