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Thanks for the link.  I too was struck by Krugman's "economists will have to learn to live with messiness."  But I don't think its only the "irrational and often unpredictable behavior" of humans that is at issue here.  My guess is that what economists (and many other academics) need to come to grips with is "evolving systems" in general, human and otherwise, systems that  are always exploring new possibilities and so are inherently "unpredictable" and inevitably transcend any effort to fully account for them "rationally."