Just caught myself off-guard and spewed on economic modelling at P3. Accidental blog entry!
"Does the absence of a workable model refute a hypothesis?" As usual, Krugman's my favourite on this. Particularly from section 'the evolution of ignorance' where he compares theory-making to early map-making. Early maps were more report-based but, as they slowly became filled in, that heuristic knowledge was lost.
"There was an extended period in which improved technique actually led to some loss in knowledge. Between the 1940s and the 1970s something similar happened to economics. A rise in the standards of rigor and logic led to a much improved level of understanding of some things, but also led for a time to an unwillingness to confront those areas the new technical rigor could not yet reach. Areas of inquiry that had been filled in, however imperfectly, became blanks. Only gradually, over an extended period, did these dark regions get re-explored."
Krugman got his Nobel prize for his work on geographical economics (the 'new economic geography'). Here he is (pdf) reflecting on that. His express purpose in creating his 'simple' core-periphery model was to show economists that geography mattered (as well as that you didn't need comparative advantage to make it work, so some places could become the core through endogenous forces alone). But the bait he used to lure neoclassical economists out of their dimensionless 'wonderland' was a model able to preserve general equilibrium.