President Trump walks on the South Lawn after returning to the White House in the early-morning hours of Nov. 27. (Alex Wong/EPA/EFE/Shutterstock) (Alex Wong/Pool/EPA-EFE/REX/Shutterstock)

Last week, President Trump assured us he was well-versed on trade ahead of his upcoming meeting with Chinese President Xi Jingping. “It’s not like, ‘Oh gee, I’m going to sit down and study it,' ” Trump said. “I know every detail. I know every stat. I know it better than anyone who’s ever known it.”

Then came his interview with the Wall Street Journal.

In the course of a conversation with the Journal’s Bob Davis, Trump fumbled a number of trade-related terms, repeatedly failed to specify what he’s asking for to end his trade war with China, and otherwise gave unspecific and generic answers. It wasn’t shocking from a president who has struggled to enunciate a clear trade strategy and agenda, but that struggle was magnified in this, an interview solely about trade with China.

Below are some key parts, with bold added for emphasis.

First, he asked Davis for help when he couldn’t summon the word for what you called a “growing country.”

TRUMP: It all began with the World Trade Organization, a disaster — a disaster. I would actually say that was perhaps — I say NAFTA was the worst trade deal ever made. I would say only — only — challenged by the WTO. That has been — if you look at China, China’s ascension was the day that the WTO was signed. It’s a one-sided deal. They were treated as a — you know, as a growing country, as a — what would you say? How would you say that?

WSJ: Developing country. Developing.

TRUMP: Developing. A developing nation. And no — and it’s never come off. They still — it’s ridiculous. The World Trade Organization is absolutely unfair to the United States, and they’re going to have to change their ways. They’re going to have to change.

Okay, so maybe you could forgive a guy for momentarily forgetting the terminology. He has said he knows more about this issue than anyone, but everyone has their moments.

But later, Trump does it again, repeatedly transposing the word “tariff” with “interest rate."

TRUMP: So, but what I’m saying is that I am very happy with what’s going on right now. We’ve only used a small portion of what we have to use because I have another $267 billion [in imports] to go if I want, and then I’m also able to raise interest rates. And we have money that is pouring right now, pouring —

WSJ: When you say interest rates, do you mean — do you mean tariffs, as opposed to interest rates?

TRUMP: I’m sorry, the rate, the 25 percent rate —

WSJ: Yeah, yeah, yeah. OK.

TRUMP: Without even doing any more.

WSJ: Yeah.

So Davis corrects Trump, and Trump says “sorry” and that he was referring to the 25 percent tariff. But then, he immediately calls the tariff an “interest rate” again — twice.

TRUMP: We have money that is pouring into our treasury right now, and on January 1 it’ll become much more so. And here’s the story: If we don’t make a deal, then I’m going to put the $200 — and it’s really $67 — billion additional on at an interest rate between 10 and 25 depending.

WSJ: Including even iPhones and laptops and things that people would know?

TRUMP: Maybe. Maybe. Depends on what the rate is. I mean, I can make it 10 percent and people could stand that very easily. But if you read that recent poll that came out, we’re only being — most of this is being — the brunt of it is being paid by China. You saw that.

Much like Trump seems to misunderstand what a trade deficit is — he views any deficit as money heading out the door, when that’s not really how it works — here he seems to think tariffs are some kind of “interest rate.” They aren’t. Interest is an accruing amount of money related to a loan; tariffs are a one-time tax on imports.

Perhaps the most puzzling thing about the interview, though, is Trump’s repeated failure to lay out any real terms. For a guy who launched a trade war, you’d think he’d have some sense for how we might reach a truce. Nowhere in this interview, though, does Trump offer specifics.

To wit:

WSJ: Let me ask you also, I mean, so you gave advice to the — to U.S. business. What advice would you give to the Chinese who are trying to decide how to deal with you?

TRUMP: Make a fair deal. The only deal that would really be acceptable to me — other than obviously we have to do something on the theft of intellectual property, right — but the only deal would be China has to open up their country to competition from the United States.

Okay, that’s half an answer. “Do something on the theft of intellectual property.” But what is the something? “Open up their country to competition from the United States.” Okay, how?

Davis tries to ascertain that answer, without much luck.

WSJ: Huh. Do you think you will go ahead with the tariffs on the cars?

TRUMP: If they don’t make a fair deal with us, I’d do it in about 12 minutes.

WSJ: Huh.

TRUMP: It depends whether or not they make a fair deal. So far they’re — you know, we talk about it. So far they’re talking about a deal, but it’s all talk. And I’m not going to make the kind of deal that the U.K. made, believe me.

DAVIS: What do you want them to do?

TRUMP: Huh?

DAVIS: What would you like them to do? What would be a fair deal?

TRUMP: A fair deal is that they have to take down their barriers and that they have to start — stop charging us massive taxes for our people — and also their standards. For instance, they’ll create a standard — we’ll make a product, and they’ll make a standard that’s different than the product, lower or higher. But it’s different. So then our product can’t come into the EU. They do that all the time, like with medical equipment, OK? But they have to take down their barriers and they have to take off the taxes. And, frankly, they have to start treating our companies better, because they sue all of our companies for billions and billions of dollars. They’re picking up all this money from our companies. We should be the ones to sue our companies.

These are all generalities. Davis tries to get Trump to give some specifics, and Trump basically keeps describing the problem that needs to be fixed. Take down barriers! Stop gaming the system! Do “something” about intellectual property. But those aren’t prescriptions; they are just things that are bad that need to be made good.

It all harks back to the immigration debate from earlier in this Congress. Trump was never terribly clear about what he wanted and even seemed allergic to policy details. That left lawmakers to try to figure it out and then bring Trump the package. But when they did bring him the package — a package that seemed to meet the loose parameters he had set — he rejected it and they were dumbfounded.

But perhaps even more than immigration, trade is an issue on which Trump apparently feels strongly and has been pressing his case for years and decades. You’d think, if there was an issue on which he knew his list of demands and understood things, this would be it.

This interview — and many others before it — suggest he doesn’t.