> ... but economists lack rigor, and would rather live in their "supply meets demand, actors are rational, and the market is in equilibrium" fantasy-land.

No, that's not why economics is in the state it's in. The reason economics is full of theorems that only hold in highly stylized worlds is that economics is hard.

Betrand Roehner provides an insightful classification of problems in the natural and social sciences by their level of complexity.[1] Two-body problems (like most of those in classical mechanics) are the least complex. N-body problems in which the interactions are local and the bodies are homogenous (like many problems in statistical mechanics) occupy the next level. At the third level of complexity are homogenous N-body problems with long-range interactions. And at the fourth level are heterogeneous N-body problems; these include lots of hard problems, like regulation of gene expression, morphogenesis ... and pretty much all interesting problems in economics and the social sciences.

Yes, I just said economics is harder than physics. (Well, it's harder than the physics physicists have been able to figure out so far.) And the difficultly of the problems is compounded by the difficultly of doing experiments in economics and the social sciences; you can't measure and tinker with a self-contained version of society in a lab somewhere. Is it any surprise then that most of economics doesn't really tell us anything directly applicable to the real world?

> ... mainstream economists only study basic calculus, linear algebra, and statistics, not ODEs, and don't believe anything they don't understand. A 50 year old professor (or central banker) isn't going to go back to school and sit in a class with sophomore engineers, just to be able to understand what "complexity theorists" and "econophysists" are talking about, so they just pretend that it doesn't exist. There's no conspiracy, they just don't read or teach anything more mathematically advanced than IS-LM (which is stone age).

You could not be more wrong. Economists, at least those from good programs, have great quantitative training. Pick up any copy of Econometrica if you don't believe me.[2] The mathematical tools used by financial economists, in particular, are largely the same as those used by statistical physicists, which is why so many physics PhDs end up working in finance. (Brownian motion, power-law distributions, etc. were all first described in an economic context.) Informed criticisms of the profession usually comes from the other side, e.g., that top economics journals are full of mathematical fireworks and devoid of reference to the real world.

And IS-LM has not been a part of mainstream macroeconomics since at least the early 1970s. It is still taught in some intro undergrad macro courses (precisely because it requires no mathematical sophistication to understand, I suppose), but it is not a part of the graduate curriculum or a part of the way macroeconomists comprehend the workings of the economy. Your citing it illustrates how little you know of what you speak.[3]

1. http://books.google.com/books?id=LEzfZ-Z98V0C&lpg=PA10&#...

2. http://www.econometricsociety.org

3. There was recently some hullabaloo in the economics blogosphere of the place of IS-LM in economics pedagogy. See, e.g., http://marginalrevolution.com/marginalrevolution/2011/10/put...