The Sanders campaign has brought out a lot of idealism and energy that the progressive movement needs. It has also, however, brought out a streak of … - Paul Krugman

When the economy is in a depression, scarcity ceases to rule. Productive resources sit idle, so that it is possible to have more of some things without having less of others; free lunches are all around. As a result, all the usual rules of economics are stood on their head; we enter a looking-glass world in which virtue is vice and prudence is folly. Thrift hurts our future prospects; sound money makes us poorer. Moreover, that's the kind of world we have been living in for the past several years, which means that it is a kind of world that students should understand. […] Depression economics is marked by paradoxes, in which seemingly virtuous actions have perverse, harmful effects. Two paradoxes in particular stand out: the , in which the attempt to save more actually leads to the nation as a whole saving less, and the less-well-known , in which the willingness of workers to protect their jobs by accepting lower wages actually reduces total employment. […] In times of depression, the rules are different. Conventionally sound policy—s, a firm commitment to —helps to keep the economy depressed. Once again, this is not normal. Most of the time we are not in a depression. But sometimes we are—and 2013, when this chapter was written, was one of those times.

Like any major intellectual contribution, Keynes's ideas were bitterly criticized. To many people it seems obvious that massive economic slumps must have deep roots. To them, Keynes's argument that they are essentially no more than a problem of mixed signals, which can be cured by printing a bit more money, seems unbelievable.

Now I’m not saying that Keynes was right about everything, that we should treat The General Theory as a sort of secular bible - the way that Marxists treat Das Kapital. But the essential truth of Keynes’s big idea - that even the most productive economy can fail if consumers and investors spend too little, that the pursuit of sound money and s is sometimes (not always!) folly rather than wisdom - is as evident in today’s world as it was in the 1930s. And in these dangerous days, we ignore or reject that idea at the world economy’s peril.