The final argument I hear about the renminbi is that it’s useless to make demands, because the Chinese will just get their backs up, refusing to bow to external pressure. The right answer is, so?

Here’s how the initial phases of a confrontation would play out – this is actually Fred Bergsten’s scenario, and I think he’s right. First, the United States declares that China is a currency manipulator, and demands that China stop its massive intervention. If China refuses, the United States imposes a countervailing duty on Chinese exports, say 25 percent. The EU quickly follows suit, arguing that if it doesn’t, China’s surplus will be diverted to Europe. I don’t know what Japan does.

Suppose that China then digs in its heels, and refuses to budge. From the US-EU point of view, that’s OK! The problem is China’s surplus, not the value of the renminbi per se – and countervailing duties will do much of the job of eliminating that surplus, even if China refuses to move the exchange rate.

And precisely because the United States can get what it wants whatever China does, the odds are that China would soon give in.

Look, I know that many economists have a visceral dislike for this kind of confrontational policy. But you have to bear in mind that the really outlandish actor here is China: never before in history has a nation followed this drastic a mercantilist policy. And for those who counsel patience, arguing that China can eventually be brought around: the acute damage from China’s currency policy is happening now, while the world is still in a liquidity trap. Getting China to rethink that policy years from now, when (one can hope) advanced economies have returned to more or less full employment, is worth very little.