Various assumptions employed by mainstream economists appear to be of an arbitrary nature. The assumptions seem to be detached from the real world.
For example, in order to explain the economic crisis in Japan, the famous mainstream economist Paul Krugman employed a model that assumes that people are identical and live forever and that output is given. Whilst admitting that these assumptions are not realistic, Krugman nonetheless argued that somehow his model can be useful in offering solutions to the economic crisis in Japan.
The employment of assumptions that are detached from the facts of reality originates from the writings of Milton Friedman. According to Friedman, since it is not possible to establish “how things really work,” then it does not really matter what the underlying assumptions of a model are. In fact anything goes, as long as the model can yield good predictions. According to Friedman,
The ultimate goal of a positive science is the development of a theory or hypothesis that yields valid and meaningful (i.e., not truistic) predictions about phenomena not yet observed…. The relevant question to ask about the assumptions of a theory is not whether they are descriptively realistic, for they never are, but whether they are sufficiently good approximation for the purpose in hand. And this question can be answered only by seeing whether the theory works, which means whether it yields sufficiently accurate predictions.
Observe that on this way of thinking, the formation of the view regarding the real world is arbitrary – in fact, anything goes as long as the model could generate accurate forecasts.
In his Philosophical Origins of Austrian Economics (Mises Institute Daily Articles June 17 2006), David Gordon wrote that Bohm Bawerk maintained that concepts employed in economics must originate from the facts of reality – they need to be traced to their ultimate source. If one cannot trace it the concept should be rejected as meaningless.
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