I was at the ASSAs in Chicago this past weekend.  One of the most interesting panels I went to was this one, on Advances in Open Economy Macroeconomics. Among other big names, Ken Rogoff was there, as the discussant for a rather strange paper by Pierre-Olivier Gourinchas and Helene Rey.
The Gourinchas and Rey paper, like much of mainstream macro these days, made a big deal of how different everything is at the zero lower bound. Rogoff wasn’t having it. Here’s a rough transcript of what he said:
The obsession with the zero lower bound is encouraging all kinds of wacko ideas. People are saying that at the ZLB, productivity increases are bad (Eggertsson/Krugman/Summers), protectionism is good (Eichngreen), price flexibility is bad, and so on.
But there is an emerging literature that says economists are taking the zero lower bound too literally. In fact, getting negative rates is not that hard. So before you take seriously these, let’s say, very creative ideas, it would be simpler to think about getting rid of the zero bound.
There are lots of ways to do it. I talk about some in my book, but people already understood this back in the 1930s. There was Robert Eisler’s proposal to have banks accept cash deposits at a discount, for instance, which would have effectively created negative rates. If Keynes had read Eisler, he might have gone in a different direction.  It’s a very old idea — Kublai Khan did something similar. There will be pushback from the financial sector, of course, who think negative rates will be costly for them, but fundamentally it is not hard to do.
These rather striking comments crystallized something in my mind. What is the big deal about the ZLB? For mainstream macroeconomists, including Gourinchas and Rey in this paper, the reason the ZLB matters is that it prevents the central bank form setting an interest rate low enough to keep output at potential.  It’s precisely this that makes inapplicable the conventional analysis of a nonmonetary problem of allocating scarce resources between alternative ends, and requires thinking about other entry points. If the central bank can’t solve the problem of aggregate demand then you have to take it seriously, with all the wacko and/or creative stuff that follows.
In the dominant paradigm, this is a specific technical problem of getting interest rates below zero. Solve that, and we are back in the comfortable Walrasian world. But for those of us on the heterodox side, it is never the case that the central bank can reliably keep output at potential — maybe because market interest rates don’t respond to the policy rate, or because output doesn’t respond to interest rates, or because the central bank is pursuing other objectives, or because there is no well-defined level of “potential” to begin with. (Or, in reality, all four.) So what people like Gourinchas and Rey, or Paul Krugman, present as a special, temporary state of the economy, we see as the general case.
One way of looking at this is that the ZLB is a device to allow economists like Krugman and Gourinchas and Rey — who whatever their scholarly training, are aware of the concrete reality around them — to make Keynesian arguments without forfeiting their academic respectability. You can understand why someone like Rogoff sees that as cheating. We’ve spent decades teaching that the fundamental constraint on the economy is the real endowment of resources and technology; that saving boosts growth; that trade is always win-win; that money and finance matter only in the short run (and the short run is tolerably short). The practical problem of negative policy rates doesn’t let you forget all of that.
Which, if you turn it around, perhaps reflects well on the ZLB crowd. Maybe they want to forget all that? Maybe, you could say, they take the zero lower bound seriously because they don’t take it literally. That is, they treat it as a hard constraint precisely because they are aware that it is only a stand-in for a deeper reality.
 The big annual economics conference. It stands for Allied Social Sciences Association — the disciplinary imperialism is right there in the name.
 This was an odd thing for Rogoff to say, since of course while Keynes didn’t discuss Eisler as far as I know, he talks at length about the similar proposals for depreciating cash of Silvio Gesell and Major Douglas. Notoriously he says these “brave cranks and heretics” have more to offer than Marx.
 Gourinchas and Rey are reality-based enough to say “the policy rate,” not “the interest rate.”
EDIT: Added the seriously-but-not-literally phrasing as suggested by Steve Roth on Twitter.