What saved the economy, and the New Deal was the enormous public-works project known as World War II, which finally provided a fiscal stimulus adequa… - Paul Krugman

Here, then, is a revised version of Marshall's rules: (1) Figure out what you think about an issue, working back and forth among verbal intuition, evidence, and as much math as you need. (2) Stay with it till you are done. (3) Publish the intuition, the math, and the evidence - all three - in an economics journal. (4) But also try to find a way of expressing the idea without the formal apparatus. (5) If you can, publish that where it can do the world some good.

It is important to realize that even now Fed officials are not quite sure how they pulled this rescue off. At the height of the crisis it seemed entirely possible that cutting interest rates would be entirely ineffectual—after all, if nobody can borrow, what difference does it make what the price would be if they could? And if everyone had believed that the world was coming to an end, their panic might—as in so many other countries—have ended up being a self-fulfilling prophecy. In retrospect Greenspan seemed to have been like a general who rides out in front of his demoralized army waves his sword and shouts encouragement, and somehow turns the tide of battle: well done, but not something you would want to count on working next time.

The phenomenon of recessions puzzled many economists in the early years of this century, and led many of them produce their worst work. Thorstein Veblen went from his brilliant Theory of the Leisure Class to write a really terrible book () purporting to explain economic slumps. Joseph Schumpeter, whose magnificent vision of the "creative destruction" inherent in capitalist growth continues to inspire many economists, wrote a turgid, almost meaningless two-volume study, Business Cycles. Marxists gleefully seized upon the biggest recession of all, the Great Depression of the 1930s, as evidence of the irrationality of capitalism; yet they never offered a good explanation of why and how such things happen, just assurances that socialism would cure them.
It fell to the British economist John Maynard Keynes to provide a clear story about what happens during a recession, and some useful advice about how to get out of one.