Paul Krugman is upset about some pretty fanciful accounts of what supposedly happened during the Great Depression, and I don’t blame him. He also wonders whether economics is a progressive science (I am using the word ‘science’ in its German sense). Well, one of the things that philosophers of science have argued about in the past is whether, when you have a paradigm shift, you end up losing knowledge, and it’s pretty clear what has happened in this instance.

I recently came across this quotation from Mark Blaug’s 1980 book on the methodology of economics which seems worth quoting, given when it was written:

At this point, it is helpful to note what methodological individualism strictly interpreted…would imply for economics. In effect, it would rule out all macroeconomic propositions that cannot be reduced to microeconomic ones, and since few have yet been so reduced, this amounts to saying goodbye to almost the whole of received macroeconomics. There must be something wrong with a methodological principle that has such devastating implications.*

Now, as Krugman points out, this ain’t necessarily so. (See his point 5 in the last of the three links, and see this paper for an example of how you can have all the theoretical bells and whistles these days and still make a sensible argument.) But there is no doubt that a lot of people have been more than happy to say goodbye to the whole of received macroeconomics — for example, I have been reliably informed that a well-known department stopped teaching its undergraduates IS-LM just before the crisis hit in 2008. And the result is that you had people seriously peddling the line that austerity would be expansionary in the wake of the biggest downturn since the 1930s — and these claims were influential in Europe, it seems clear, in the fateful spring and summer of 2010.

One lesson is that it is one thing to play counter-intuitive intellectual parlour games in order to get tenure at a fancy university, but another thing entirely to say something about the real world. For that you need a little common sense.

Another lesson is that economists need at least some training in economic history. No-one with the slightest feeling for historical reality could believe that the Great Depression was due to supply side forces, for example. I observe that Krugman, along with such luminaries as Maurice Obstfeld and Ken Rogoff, did his graduate work in MIT, and I surmise (without having any inside knowledge on the matter) that all three were exposed to Charlie Kindleberger and Peter Temin. They are all distinguished theorists, but also have a historical sensitivity, and this makes them better economists — if your definition of a good economist includes the ability to say sensible things about our very messy real world.

One of the most important things that a bit of history gives you is a sense of the importance of context. A model will work very well in some technological or institutional contexts, but not in others. For example, the Reverend Malthus devised a model that did a pretty decent job of describing the world up to the point that he started writing, but which soon became essentially irrelevant in the century that followed, at least in the richer countries of the world. (He had an economist’s sense of timing.) Sometimes the world is well-described by Keynesian models, and sometimes it is not. And so on.

If the only thing that economic history did was protect us from one-size-fits-all merchants, it would still be worth the price of admission.

*I am looking at the 2nd edition, published in 1992, but I am betting that this sentence dates from the 1980 edition.