The president’s plan for reciprocal tariffs sounds good in theory. But there was a reason the United States abandoned the approach a century ago. The gains would be few and the costs enormous.

Trump calls it unfair that some countries apply higher tariffs to specific American goods than the U.S. applies back. A new executive order seeks to change that.

President Donald Trump is taking a blowtorch to the rules that have governed world trade for decades. The “reciprocal’’ tariffs that he announced Thursday are likely to create chaos for global businesses and conflict with America’s allies and adversaries alike.