To: JohnM who wrote (103547 ) 2/8/2009 9:58:41 PM From: Mary Cluney Read Replies (1) | Respond to of 542010 <<<More than a few cheap shots.>>>January 30, 2009, 4:44 pm Saving, investment, Keynes, evolution If there was one essential element in the work of John Maynard Keynes, it was the demolition of Say’s Law — the assertion that supply necessarily creates demand. Keynes showed that the fact that spending equals income, or equivalently that saving equals investment, does not imply that there’s always enough spending to fully employ the economy’s resources, that there’s always enough investment to make use of the saving the economy would have had it it were at full employment. Getting to that realization was an awesome intellectual achievement. That’s why it’s deeply depressing to find, not that people like Eugene Fama disagree with Keynes’s conclusions — that’s OK, no theory is sacred — but that they’re obviously completely unaware of the whole argument. One of Brad DeLong’s commentators compares what’s going on to the discovery that some eminent biologists are creationists, but it’s actually worse than that: it’s like discovering that some eminent biologists have never heard of the theory of evolution and the concept of natural selection. How did we get to this point? Perhaps a more balanced view: 13. January 30, 2009 7:13 pm Rather than comparing Say’s law to creationism, might it be more accurate to think of the difference between Say and Keynes akin to the difference between Newton and Einstein; the earlier a limited and idealized case (that yet contains some truths) and the latter bringing newer insights to bear. We should be careful not to be historically arrogant given that Say lived about 300 years ago. Will anyone be discussing “Krugman’s law” (whatever that might be) in 2300?