Grasping Reality on TypePad, by Brad DeLong

Joe Smith tells us about Johnny von Neumann on theory-mining:

Jean-Claude Trichet Rejects the Counsels of History: Joe Smith said...

Economists have none of that. The "economic principles" underpinning their theories are a fraud--not bedrock truths but mere knobs twiddled and tunes so that the right conclusions come out of the analysis.

John Von Neumann said: "With four parameters I can fit an elephant, and with five I can make him wiggle his trunk."

Any theory that requires fiddling with the parameters to make it work is no theory at all.