After his Keynesianism-is-gay remarks got him in trouble, Niall Ferguson did the right thing and offered a straightforward, no excuses apology. Unfortunately, it seems that he has reverted to type; sigh.

But this does seem to call for an update on a subject I have written about occasionally: the remarkable way in which the Great Recession, by bringing us back into a world of persistent inadequate demand, has unleashed a sort of reign of error among anti-Keynesian economists and pundits. And I’m not talking about the usual Heritage or Cato hacks; I’m talking about people with serious reputations either for research or for seemingly judicious commentary.

Oh, and by “error” I don’t mean “views I disagree with”; I mean raw conceptual or empirical banana-peel episodes, the kind of thing that defenders of these men (who have a lot of defenders) try to justify not by claiming that they were right, but by claiming that they didn’t say what they did, in fact, say....