As many people have pointed out, this is junk economics. Except at times of mass unemployment, trade deficits aren’t a subtraction from the economies that run them, nor are trade surpluses an addition to the economies on the other side of the imbalance. Over all, the U.S. trade deficit is just the flip side of the fact that America attracts more inward investment from foreigners than the amount Americans invest abroad. Trade policy has nothing to do with it.

Beyond this conceptual confusion, there’s a raw fact few people — and, as far as I can tell, nobody in the Trump administration — seem to appreciate: China no longer runs big trade surpluses.

This wasn’t always true. A decade ago, China’s current account surplus — a broad measure that includes trade in services and income from investments abroad — was more than 9 percent of G.D.P., a very big number. In 2017, however, its surplus was only 1.4 percent of G.D.P., which isn’t much. Meanwhile, the U.S. ran a current account deficit of 2.4 percent of G.D.P., a bit bigger, but also much smaller than the imbalances of the mid-2000s.

But in that case, why is “bilateral” trade between the U.S. and China so unbalanced? The answer is that it’s largely a kind of statistical illusion. China is the Great Assembler: it’s where components from other countries, like Japan and South Korea, are put together into consumer products for the U.S. market. So a lot of what we import from China is really produced elsewhere.

It’s not clear why we should demand that China stop playing that role. Indeed, it’s not clear that China could even do much to reduce its bilateral surplus with the U.S.: To do so, it would basically have to have a completely different economy. And this just isn’t going to happen unless we have a full-blown trade war that shuts down much of the global economy as we know it.

Now, Trump himself might be O.K. with large-scale deglobalization. But as we’ve seen, his beloved stock market hates the idea, and with good reason: Businesses have invested heavily on the assumption that a closely integrated global economy is here to stay, and a trade war would leave many of those investments stranded.

Oh, and a trade war would also devastate much of pro-Trump rural America, since a large share of our agricultural production — including almost two-thirds of food grains — is exported.

And that’s why things seem so incoherent. One day Trump talks tough on trade; then stocks fall, and his advisers scramble to say that the trade war won’t really happen; then he worries that he’s looking weak, and tweets out more threats; and so on. Call it the art of the flail.