In particular, we should avoid the urge to levy tit-for-tat tariffs on imports of products from the United States, such as the Europeans are threatening to impose on American motorcycles, blue jeans and bourbon. Trade war is unlike real war in one crucial respect: the guns are pointed inward. The chief victims of any tariffs the Trump administration might impose in the name of protecting the American steel industry are other Americans: the industries that use the suddenly dearer steel, imported or domestic, in production; the consumers of the products they make, those costs having been passed on in higher prices; the workers in still other industries, consumers having that much less income left to spend on other things; and so on.

So it is with any tariffs we might impose in retaliation. The proper response to your neighbour shooting himself in the foot is not to shoot yourself in the foot — a point someone might make to Ontario Premier Kathleen Wynne, for example, whose proposed Fairness in Procurement Act, advertised as retaliation against “Buy American” measures that would limit Canadian firms’ ability to bid on government procurement in the U.S., will simply limit competition for the taxpayer’s dollar and drive up prices in the Ontario procurement market…

The point has to be re-emphasized: these people are not normal — not only Trump, but his Commerce Secretary, Wilbur Ross, and even more his trade adviser, Peter Navarro. All governments play at being protectionist from time to time: all have powerful interests to appease, or elections to win, or some larger strategic game in mind. With these people it’s genuine. They really do think the trade deficit is some kind of index of America’s net worth, and not simply an accounting identity, the necessary counter-entry on the national ledger to a capital surplus.