The people from the concrete steppes don't get this. Me giving you $1,000 is a concrete action. It's real; they can see it. You expecting me to do something if you were to do something that you won't in fact do is not something concrete. It's not even an expectation about what will happen. It's an expectation about something that won't happen. It's an expecation about a counterfactual conditional. There's nothing more airy fairy than that! But that airy fairy expectation about a counterfactual conditional has real consequences.

Suppose I lend you $1,000, at 0% interest. But I warn you that as soon as you spend that $1,000, or lend it to someone else to spend, I will immediately make you repay the loan, or else raise the interest rate high enough to make you regret spending it or lending it. You will not spend that $1,000. You will keep it somewhere safe. What I actually do (giving you the $1,000 at 0% interest) doesn't matter. It's what you expect about what I would do (make you repay the $1,000 if you spend it) that matters.

The people from the concrete steppes see central banks print lots of money. That's a real concrete step, and real concrete steps have real concrete consequences. Printing lots of money causes lots of inflation. And the fact that lots of inflation hasn't happened yet simply means it's a lagged effect. Lags between causes and effects are real concrete things. Mechanical things have lags. Effects always follow after the causes. Sometimes soon after, but sometimes long after. Effects never come before causes.

If printing lots of money did cause people to spend it and cause inflation, then central banks would immediately put the printing presses into reverse. They would buy back the money they had printed, and burn it, to stop people spending it and causing inflation. And people expect they would do this. And no individual will spend unless he expects other individuals to spend. So nobody spends. It's a credit deadlock, created by counterfactual conditional expectations about what central banks would do if people did something that they won't do, because of those expectations.

Paul Krugman calls them "inflation derps", because they keep on ignoring the empirical evidence that falsifies their predictions of high inflation. OK. But they are also people from the concrete steppes. They cannot see the thing that is causing their predictions to fail, because that thing is not a concrete thing. And lags between cause and effect are concrete things. It's the lack of confidence fairy that is falsifying their predictions. A commitment by the central bank not to do what people expect it to do, to change those counterfactual conditional expectations, would change things. Something like an NGDP level path target. "Yes, we will let you spend that $1,000 we lent you at 0% interest."