This evening I recalled this statement of John Maynard Keynes:
The ideas of economists and political philosophers, both when they are right and when they are wrong, are more powerful than is generally understood. Indeed, the world is ruled by little else. Practical men, who believe themselves to be quite exempt from any intellectual influences, are usually the slaves of some defunct economist.
The General Theory of Employment, Interest and Money (Macmillan, London, 1949), p. 383
What Keynes should have said is this:
Economists and political philosophers -- on those rare occasions when they succeed in modeling human behavior -- are the slaves of the living and dead persons whose behavior they observed and happened (luckily) to explain correctly.