Belatedly, I have just seen a column by John Kay in the FT of 13 April 2010 (subscribers only), entitled:  “Economics may be dismal, but it is not a science.” His column reminded me of Stephen Toulmin’s arguments in his book Cosmopolis about the universalizing tendencies of modern western culture these last four centuries, which I discussed here.
An excerpt from Kay’s column:

Both the efficient market hypothesis and DSGE [Dynamic Stochastic General Equilibrium models] are associated with the idea of rational expectations – which might be described as the idea that households and companies make economic decisions as if they had available to them all the information about the world that might be available. If you wonder why such an implausible notion has won wide acceptance, part of the explanation lies in its conservative implications. Under rational expectations, not only do firms and households know already as much as policymakers, but they also anticipate what the government itself will do, so the best thing government can do is to remain predictable. Most economic policy is futile.
So is most interference in free markets. There is no room for the notion that people bought subprime mortgages or securitised products based on them because they knew less than the people who sold them. When the men and women of Goldman Sachs perform “God’s work”, the profits they make come not from information advantages, but from the value of their services. The economic role of government is to keep markets working.
These theories have appeal beyond the ranks of the rich and conservative for a deeper reason. If there were a simple, single, universal theory of economic behaviour, then the suite of arguments comprising rational expectations, efficient markets and DSEG would be that theory. Any other way of describing the world would have to recognise that what people do depends on their fallible beliefs and perceptions, would have to acknowledge uncertainty, and would accommodate the dependence of actions on changing social and cultural norms. Models could not then be universal: they would have to be specific to contexts.
The standard approach has the appearance of science in its ability to generate clear predictions from a small number of axioms. But only the appearance, since these predictions are mostly false. The environment actually faced by investors and economic policymakers is one in which actions do depend on beliefs and perceptions, must deal with uncertainty and are the product of a social context. There is no universal economic theory, and new economic thinking must necessarily be eclectic. That insight is Keynes’s greatest legacy.