Economics is harder than physics; luckily it is not quite as hard as sociology. Why is economics such a hard subject? Part of the answer has to do wi… - Paul Krugman

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.

So let’s bid a not at all fond farewell to the Big Zero — the decade in which we achieved nothing and learned nothing.

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.