Physics envy part II

This is a bit old, but check out Jim Manzi criticizing economists for not being as reliable as physicists:

How does the economist know that her predictions, which sound like the physicist’s predictions, are reliable in a way that the historian’s are not? She doesn’t. Therefore the president would be wise to treat the economist’s prediction like the historian’s prediction, in that it should be subjected to useful cross-examination by laymen, weighing of technical and non-technical opinions, introspection concerning human motivation, and all the rest. Beyond this, he should always keep in mind the unreliability of such predictions, and treat the fog of uncertainty about the potential effects of our actions as fundamental when considering what to do. I’m not arguing that the economist’s output is valueless – I would no more advise a president to make a major economic decision without professional economic advice than I would advise him to make a decision about war and peace with consulting relevant historians – but I am arguing that we should be extremely humble about our ability to make reliable, useful and non-obvious predictions about the results of our economic interventions.

I was all set to write a brilliant exposition on why economics can be useful even though data are hard to come by and the models don’t perfectly capture reality.  I also planned on explaining that expert judgment is still useful and should be heeded, and was ready with an illuminating analogy to medicine.  But Noah Millman beat me to it, and did a better job than I could have.  Alas!

I will add that, as a former space physicist, physics isn’t even like physics.  Outside of fields like atomic or particle physics, data are also hard to come by and the models are greatly simplified.

From Millman’s response:

The technical expertise a doctor has is not the same as the technical expertise a physicist has – and, more importantly, we rely on the doctor developing a general capacity for good judgment in his field in a way that we do not rely on a physicist to develop in hers. But the doctor is also different from a historian. I would be very surprised if anybody actually relies on historians to help them make specific decisions. Rather, we rely on historians as repositories of a certain kind of knowledge that, we believe, is important for a society to retain and develop: for the sake our own social cohesion, to develop an appreciation of the texture of other societies, and because it is useful for developing practical wisdom in general (and I’m sure there are other good reasons – I’m not trying to be exhaustive here).

Economics is frequently taught and described as if it is physics, which would make policymakers more like engineers applying well-understood and tested principles in specific situations. But I would argue that it’s more like medicine – another field where what we know with the kind of scientific rigor that would pass muster for a physicist is dwarfed by what we know only imperfectly if at all, but where decisions have to be made constantly, and where we have strong reasons to believe that the knowledge and experience of the experts is very useful in helping us make those decisions.


    1. Hi Jim. Thanks for the comment. Frankly I’m quite flattered you read this. I will definitely check out your reply.

      I meant to, but forgot, to add in my post that I think Noah probably stretched your argument a bit further than it should have been. That is, I didn’t interpret your original post as a call to eliminate expert judgment in economics, which is what Noah appeared to accuse you of. I’ll be sure to check out your response.

      Thanks again, and please do stop in from time to time. Based on what I’ve read of your work, you might find some of this interesting!

      Happy holidays.


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