Exploring General Equilibrium

“Many of the models in the literature are not general
equilibrium models in my sense. Of those that are, most are intermediate in
scope: broader than examples, but much narrower than the full general
equilibrium model. They are narrower, not for carefully-spelled-out economic
reasons, but for reasons of convenience. I don’t know what to do with models
like that, especially when the designer says he imposed restrictions to simplify
the model or to make it more likely that conventional data will lead to reject
it. The full general equilibrium model is about as simple as a model can be: we
need only a few equations to describe it, and each is easy to understand. The
restrictions usually strike me as extreme. When we reject a restricted version
of the general equilibrium model, we are not rejecting the general equilibrium
model itself. So why bother testing the restricted version?”

Fischer Black, 1995, p. 4, Exploring General Equilibrium, The MIT Press.