Two Kinds of Economists

Dani Rodrik has an insightful (must read!) post, "Why Economists Disagree," where he identifies two types of economists, "first-best economists," and "second-best economists." The world view of the first group is based on the optimality properties of competitive markets - i.e. market outcomes lead to the "first-best" outcome, and any policy intervention is welfare reducing. The second camp understands that the assumptions on which the optimality results depend - perfect competition, perfect information, etc. - never hold in the real world; that we live in a "second-best" world where government policies can be welfare-improving.
Rodrik's "first-best economists" are the same people as the "classical" economists Keynes assaults in the introduction to the General Theory:

...The postulates of the classical theory are applicable to a special case only and not to the general case, the situation which it assumes being a limiting point of the possible positions of equilibrium. Moreover, the characteristics of the special case assumed by the classical theory happen not to be those of the economic society in which we actually live, with the result that its teaching is misleading and disastrous if we attempt to apply it to the facts of experience.

Seventy-one years later, we're still fighting the same battles. Why do so many economists and students of economics take such a naive, knee-jerk "free market" view? Again, Keynes has an answer (from ch. 3 of the General Theory):

The completeness of the Ricardian victory is something of a curiosity and a mystery. It must have been due to a complex of suitabilities in the doctrine to the environment into which it was projected. That it reached conclusions quite different from what the ordinary uninstructed person would expect, added, I suppose, to its intellectual prestige. That its teaching, translated into practice, was austere and often unpalatable, lent it virtue. That it was adapted to carry a vast and consistent logical superstructure, gave it beauty. That it could explain much social injustice and apparent cruelty as an inevitable incident in the scheme of progress, and the attempt to change such things as likely on the whole to do more harm than good, commended it to authority. That it afforded a measure of justification to the free activities of the individual capitalist, attracted to it the support of the dominant social force behind authority.

I think Rodrik and Keynes have it about right, though some say that there are actually three kinds of economists: those who can count, and those who cannot.