Spend any time around monetary officials and one word you’ll hear a lot is “normalization.” Most though not all such officials accept that now is no time to be tightfisted, that for the time being credit must be easy and interest rates low. Still, the men in dark suits look forward eagerly to the day when they can go back to their usual job, snatching away the punch bowl whenever the party gets going.

But what if the world we’ve been living in for the past five years is the new normal? What if depression-like conditions are on track to persist, not for another year or two, but for decades?

You might imagine that speculations along these lines are the province of a radical fringe. And they are indeed radical; but fringe, not so much. A number of economists have been flirting with such thoughts for a while. And now they’ve moved into the mainstream. In fact, the case for “secular stagnation” — a persistent state in which a depressed economy is the norm, with episodes of full employment few and far between — was made forcefully recently at the most ultrarespectable of venues, the I.M.F.’s big annual research conference. And the person making that case was none other than Larry Summers. Yes, that Larry Summers.

And if Mr. Summers is right, everything respectable people have been saying about economic policy is wrong, and will keep being wrong for a long time.