Again I really wish I could do all of these arguments justice because these guys are really barking up my tree.

Arnold Kling has the latest in scientific metaphors for why macroeconomics is in dire straits.

Given that the models have no credibility among researchers, why is it that they are used by policy makers, such as the president’s Council of Economic Advisers and the Congressional Budget Office? Greg Mankiw, who has been both a researcher and a policy maker, says that it is because the researchers have failed to come up with a better alternative.

Imagine if somehow we knew how to launch satellites but still believed in pre-Copernican astronomy. We would have no choice but to send satellites into space using calculations that assumed that the earth is the center of the universe.

I love these analogies. Don Boudreaux talked about a flat earth. Jim Manzi talked about a rocket ship. Various folks have mentioned phlogiston. I actually have a huge post in mind on phlogiston that I don’t know if I’ll get a chance to write.

However, the Copernican thing is just great because I think it really gets to the heart of science and engineering.

Arnold seems to be arguing that launching a satellite using pre-Copernican astronomy would be the province of fools. I argue to the contrary that it would work just fine.

Indeed, the Ptolemaic models in use at the time Copernicus released his models were more precise than those of Copernicus. They were a fundamentally worse model, for reasons that we can talk about but deal deeply with the question “what is a model.”

However, they were not less useful, they were more useful.

It was not until Johannes Kepler was able to formulate elliptical models did the Copernicans models begin to exceed the Ptolemaic models in precision.

This is because the history of science is not the history of foolish ideas being overturned by brilliant insight but the history of anamoly. Usually we have a model that is pretty good, to a point, but makes some errors we can’t explain.

In order to correct those errors sometimes we can add retrograde motion but sometimes we have to scrap the whole thing and start over. Importantly, however, scrapping an old “wrong model” for a new “right model” does not necessarily produce an immediate increase in the model’s usefulness or precision.

The old models were in use precisely because people had found ways to tweak them to give the right answers. Unless you can fully incorporate all of those tweaks in one swoop you are likely to end up with something less useful than what you are trying to replace. The hope is that when you are done tweaking your model it will beat out out what we had before.

Its also worth noting that when satellites were put into orbit the models that were used were Newtonian, which the rocket scientists knew full well were “wrong.” However, there were not useful General Relativity models at the time.

However, by the time GPS came along, it had become the case that you must use General Relativity or the estimates of your location will be off by more than is tolerable for GPS to be useful.

The point of all this is not to say that Arnold picked a bad example. It is to say that folks who are pointing out how economics is not like a science are really pointing out that they don’t realize how clunky and full of kludges other sciences are.

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