Not long after President Donald Trump’s inauguration, the administration’s economic staff went to work on a daunting task: determining tariff rates for dozens of countries to fulfill the president’s campaign pledge of imposing “reciprocal” trade barriers.

After weeks of work, aides from several government agencies produced a menu of options meant to account for a wide range of trading practices, according to three people familiar with the matter.

Instead, Trump personally selected a formula that was based on two simple variables — the trade deficit with each country and the total value of its U.S. exports, said two of the people, who spoke on the condition of anonymity to recount internal talks. While precisely who proposed that option remains unclear, it bears some striking similarities to a methodology published during Trump’s first administration by Peter Navarro, now the president’s hard-charging economic adviser. After its debut in the Rose Garden on Wednesday, the crude math drew mockery from economists as Trump’s new global trade war prompted a sharp drop in markets.

The president’s decision to impose tariffs on trillions of dollars of goods reflects two key factors animating his second term in office: his resolve to follow his own instincts even if it means bucking long-standing checks on the U.S. presidency, and his choice of a senior team that enables his defiance of those checks.

Inside and outside the White House, advisers say Trump is unbowed even as the world reels from the biggest increase in trade hostilities in a century. They say Trump is unperturbed by negative headlines or criticism from foreign leaders. He is determined to listen to a single voice — his own — to secure what he views as his political legacy. Trump has long characterized import duties as necessary to revive the U.S. economy, at one point calling tariffs “the most beautiful word in the dictionary.”

There simply isn’t any method to his madness.

At Liberal Currents, Alan Elrod writes about Trump and RFK Jr. destroying American scientific research: You’re Not Crazy. America Has Gone Mad.