Endogeneity and Me, Are Pretty Good Company

In an interesting discussion of exogenous versus endogenous this money, Nick Rowe writes:

"If we are being *very* strict about terminology, things are never 'exogenous' or 'endogenous' in themselves, but only within the context of a given model. E.g. weather is exogenous in economics models, but endogenous in meteorological models."

I think Nick is being overly instrumentalist here. To me it seems perfectly accurate to say that a bird's heartbeat is endogenous to the bird, and not merely to our model of the bird, and that the arrow I shoot at the bird in order to have it for dinner is exogenous to the bird, and not merely to our model of the bird. (But that the arrow is endogenous to my plan for getting dinner.)

Of course, "the bird" is itself an abstraction from all else around it, but I assume Nick is not shooting for absolute idealism here.

(Hat tip Murphy.)


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