What did Donald Trump do today?

He believed he'd once again solved the mystery of the "tariff shelf" for the first time.

On August 14, Trump told this story at an Oval Office press availability.

Last week they found $29 billion and they couldn't figure out where it came from. I said, check the tar—the tariff shelf. And they said, "How did you know that's where it came from?" Taking in billions and even trillions of dollars in tariffs.

On September 26, Trump told this story at an Oval Office joint press conference:

We're finding, the other day, they found $31 billion, they said, "Sir, we found thirty-one—" I said, "you mean positively, right?" They said, "Yeah, we found $31 million [sic], more than we knew," and they said, "We don't know where it came from?" I said, "Check the tariff shelf." They came back the following morning, they said, "You're right, sir, it came from the tariffs."

Today, Trump told this story at an Oval Office press availability:

They're finding money in our country now that they never knew existed. The other day — $30 billion. Where did it come from? I said, "Why don't you check the tariffs shelf?" They said, "Sir, that tariff hasn't started yet, it doesn't start until January." I said, "No, it started 2 months ago." They call back — "Sir, you're right, it's from tariffs."

In other words, Trump believes he is constantly existing in a world in which he has just now solved a mystery that had stumped his economic advisors: the source of a certain number of billions of "extra" dollars in revenue. (Where a "shelf" comes into it is still unclear.)

People suffering from cognitive or memory issues often repeat the same stories, or fall into semi-scripted "patter," in order to distract from their confusion. Familiar surroundings—like, for example, a particular room that they visit at certain times of the day—can often trigger the same train of thought over and over again. Patients exhibiting this symptom rarely understand that they are repeating themselves.

Of course, there is a grain of truth to Trump's fantasy: on a quarterly basis, the United States is currently raising something like $30 billion per quarter in "extra" revenue, paid by American consumers in the form of higher sales prices. One way of looking at that is that it is costing the average household $1,100 per year. Another is that it's about a 2% increase in revenues, which is not nearly enough to offset the tax breaks for the ultra-wealthy Trump put into the 2025 budget bill.

Trump has not told any stories where "they" called him "sir" and asked where the missing billions from those tax cuts went. 

Why does this matter?

• This is not someone who is cognitively fit for the presidency or any other job.