Some practical men do not like the idea of a thought experiment. Yet these exercises are an essential part of the growth of human knowledge. Indeed, today’s address by Ben Bernanke at the meeting of central bankers in Jackson Hole, Wyoming, makes it appropriate for one such experiment: to ask what would happen if, in the main industrial countries, currency notes were to drop from helicopters as a deliberate act of policy?

No one has explicitly argued for this as a deliberate act. But Milton Friedman raised the possibility in an essay he wrote on the “optimum quantity of money”. He mentioned the helicopter as a device to avoid discussing the intricacies of the banking system, which he had done sufficiently on other occasions. Years later, Mr Bernanke described various expedients, including quantitative easing, as being the nearest equivalent to such a drop. This led to some on Wall Street naming him “Helicopter Ben”. However, there is an important difference. QE will work through the banking system. Helicopter money is available for those fit enough to pick it up.

John Maynard Keynes raised a similar possibility during the 1930s when he said that if there was no better way of getting out of a depression, pound notes should be buried in the ground, leaving it to the well-tried forces of self interest to dig them up again.