Sunday, February 21, 2016

“When the facts change, I change my mind. What do you do, sir?”

Economics is a science of thinking in terms of models joined to the art of choosing models which are relevant to the contemporary world. It is compelled to be this, because, unlike the typical natural science, the material to which it is applied is, in too many respects, not homogeneous through time…Good economists are scarce because the gift for using "vigilant observation" to choose good models, although it does not require a highly specialised intellectual technique, appears to be a very rare one
from J. M. Keynes' letter to Harrod, 4 July 1938