re macro-economists doomed to always “fight the last war”? Are they doomed to always be explaining the last problem we had, even as a completely different problem is building on the horizon?
Well, maybe. But I think the hope is that microfoundations might prevent this. If you can really figure out some timeless rules that describe the behavior of consumers, firms, financial markets, governments, etc., then you might be able to predict problems before they happen. So far, that dream has not been realized. But maybe the current round of “financial friction macro” will produce something more timeless. I hope so.
So there we have it! This is nothing but the age-old machine dream of neoclassical economics — an epistemologically founded cyborg dream that disregards the fundamental ontological fact that economies and societies are open — not closed — systems.
If we are going to be able to show that the mechanisms or causes that we isolate and handle in our models are stable in the sense that they do not change when we “export” them to our “target systems,” they do only hold under ceteris paribus conditions and are a fortiori of limited value for understanding, explaining or predicting real economic systems. Or as the always eminently quotable Keynes wrote in Treatise on Probability(1921):
The kind of fundamental assumption about the character of material laws, on which scientists appear commonly to act, seems to me to be [that] the system of the material universe must consist of bodies … such that each of them exercises its own separate, independent, and invariable effect, a change of the total state being compounded of a number of separate changes each of which is solely due to a separate portion of the preceding state … Yet there might well be quite different laws for wholes of different degrees of complexity, and laws of connection between complexes which could not be stated in terms of laws connecting individual parts … If different wholes were subject to different laws qua wholes and not simply on account of and in proportion to the differences of their parts, knowledge of a part could not lead, it would seem, even to presumptive or probable knowledge as to its association with other parts … These considerations do not show us a way by which we can justify induction … No one supposes that a good induction can be arrived at merely by counting cases. The business of strengthening the argument chiefly consists in determining whether the alleged association is stable, when accompanying conditions are varied … In my judgment, the practical usefulness of those modes of inference … on which the boasted knowledge of modern science depends, can only exist … if the universe of phenomena does in fact present those peculiar characteristics of atomism and limited variety which appears more and more clearly as the ultimate result to which material science is tending.
Source: Lars P. Syll