President Donald Trump's economic policies have shaken long-standing trade deals, rattled global supply chains, and worried American businesses that depend on imports.

All of it—the tariffs, the threats to kill NAFTA, the trade war with China—reflects a worldview that can be summed up neatly with three simple words: "Trade is bad."

That's what Trump reportedly scribbled in the margins of a speech he was editing with then–staff secretary Rob Porter, according to an excerpt from a forthcoming book by the Pulitzer-winning reporter Bob Woodward. On Wednesday, Axios reported several stunning trade-related tidbits from the book, Fear, which is due to be released next week. (Other juicy bits were leaked to The Washington Post and CNN on Tuesday.) The portions of the book released this week paint a picture of a White House in chaos, led by a president who is underprepared for and overwhelmed by the office he holds.

White House economic adviser Gary Cohn tried several times to engage Trump over his anti-trade views, Woodward writes.

"Why do you have these views [on trade]?" Cohn asked Trump, according to Woodward.

"I just do," Trump reportedly replied. "I've had these views for 30 years."

Trump has indeed held a favorable view of tariffs for decades. Trump's hostility toward China—and, more importantly, the underlying idea that trade is a zero-sum game with winners and losers—is not the product of his late-in-life transformation from hotel mogul to reality TV star to politician. It fits with the rest of the nationalist economic message he used to catapult himself to the top of an increasingly nationalistic Republican Party, but it has roots that go deeper than that.

For example, here's something Trump said in a 1990 interview with Playboy:

I think our country needs more ego, because it is being ripped off so badly by our so-called allies; i.e., Japan, West Germany, Saudi Arabia, South Korea, etc. They have literally outegotized this country, because they rule the greatest money machine ever assembled and it's sitting on our backs. Their products are better because they have so much subsidy. We Americans are laughed at around the world for losing $150 billion year after year, for defending wealthy nations for nothing, nations that would be wiped off the face of the earth in about 15 minutes if it weren't for us. Our "allies" are making billions screwing us.

In the same interview, Trump talked about how he would like to put "a tax on every Mercedes-Benz rolling into this country and on all Japanese products." He also said he could someday be president because "the working guy would elect me. He likes me."

For a man who seems to have few guiding stars, Trump's economic nationalism has been remarkably consistent. No wonder, then, that the 1990 Playboy interview has become something of a Rosetta Stone for understanding Trump, with foreign officials studying it for clues about how to woo the president.

It's equally unsurprising that the president has apparently done little self-reflection over the past three decades about these views. Now he's getting an up-close view of how tariffs warp the economy, create international tensions, and invite opportunities for wanton cronyism—all while failing to achieve their primary policy goals, of course. But that doesn't seem to be causing any second thoughts.

Just last month, representatives from more than 300 American businesses and trade associations descended on D.C. for six days of hearings about Trump's plan to expand his trade war with China by targeting another $200 billion in import with new tariffs. Despite their widespread opposition—and despite warning signs from the economy—Trump is reportedly pressing ahead with the new trade barriers, which could be announced before the end of the week.

Trade is, of course, not bad. It is in fact quite good. But Trump's economic illiteracy isn't the biggest problem here. It's his inability or unwillingness to learn anything new or to challenge his long-held beliefs.

"He's an idiot," John Kelly, the president's chief of staff, says in a portion of Woodward's book excerpted Tuesday by The Washington Post. "It's pointless to try to convince him of anything." (Kelly has denied this.)

When Cohn confronted Trump about his views on trade, the president reportedly couldn't offer a better defense than the fact that he'd believed these things for a long time.

"I had the view for 15 years I could play professional football," Cohn replied, according to Woodward. "It doesn't mean I was right."