Suppose that Trump were to impose tariffs on a wide range of goods — say, the 10 percent across-the-board tariff that was floated before he took office. This would directly benefit industries that compete with imports, but that’s not the end of the story.

Even if we ignore the damage to industries that use imported inputs, any direct job creation from new tariffs would be offset by indirect job destruction. The Federal Reserve, fearing inflationary pressure, would raise interest rates. This would squeeze sectors like housing; it would also strengthen the dollar, hurting U.S. exports.

Claims that protectionism would inevitably cause a recession are overblown, but there’s every reason to believe that these indirect effects would eliminate any net job creation.

Then there’s the response of other countries. International trade is governed by rules — rules America helped put in place. If we start breaking those rules, others will too, both in retaliation and in simple emulation. That’s what people mean when they talk about a trade war.

And it’s foolish to imagine that America would “win” such a war. For one thing, we are far from being a dominant superpower in world trade — the European Union is just as big a player, and capable of effective retaliation (as the Bush administration learned when it put tariffs on steel back in 2002). Anyway, trade isn’t about winning and losing: it generally makes both sides of the deal richer, and a trade war usually hurts all the countries involved.

I’m not making a purist case for free trade here. Rapid growth in globalization has hurt some American workers, and an import surge after 2000 disrupted industries and communities. But a Trumpist trade war would only exacerbate the damage, for a couple of reasons.

One is that globalization has already happened, and U.S. industries are now embedded in a web of international transactions. So a trade war would disrupt communities the same way that rising trade did in the past. There’s an old joke about a motorist who runs over a pedestrian, then tries to fix the damage by backing up — running over the victim a second time. Trumpist trade policy would be like that.