Robert Skidelsky has written a piece in the New York Sun that posits the claim that the conservative cycle is ending in Washington and the liberal cycle is beginning. The article is definitely worth a read, but I found the following pithy paragraph to be of particular interest:
The classical economics of the 1920s abstracted from the problem of unemployment by assuming that it did not exist. Keynesian economics, in turn, abstracted from the problem of official incompetence and corruption by assuming that governments were run by omniscient, benevolent experts. Today’s “new classical economics” abstracted from the problem of uncertainty by assuming that it could be reduced to measurable, or hedgeable, risk.
Although I would quarrel a bit with the first sentence, I think that the subsequent claims are dead on.