It is just over three score years and ten since the Great Depression. Judged by its rejection of the plan put forward by Hank Paulson, US Treasury secretary, Congress believes it is time to risk another one. That slump was, arguably, the greatest catastrophe of the 20th century: it was, among other things, responsible for the events that led to the second world war – not least Hitler's rise. One can only imagine what horrors a depression might bring now?

Such forebodings must seem exaggerated. So, I expect, they will be. But that dire outcome is no longer impossible, not because a slump is inevitable, far from it, but because action is needed to prevent one.

We are watching the disintegration of the financial system. Finance is the web of intermediation binding economic agents to one another, across both space and time. Without it, no modern economy can survive. Yet that is now threatened, with the ongoing collapse in trust and flight to safety. We can indeed run this experiment. But why should we?