The first time Donald Trump published a tweet about building a wall along the U.S./Mexico border was in early August 2014. “Secure the border!” the all-caps missive read. “Build a wall!”

The publication date serves as a reminder that the Republican has had more than five years to come up with a compelling argument in support of his signature domestic policy priority. By any reasonable measure, Trump hasn’t spent that time wisely.

A Washington Post analysis explained yesterday:

“Need to stop Drugs, Human Trafficking, Gang Members & Criminals from coming into our Country,” Trump wrote with his idiosyncratic capitalization. Later in the day he added that Democrats want an “Open Southern Border and the large scale crime that comes with such stupidity.” Democrats don’t want “open borders,” of course, but oppose the construction of the wall in part because it’s so central to Trump’s priorities. But the bigger reason Democrats oppose construction of the wall is that Trump’s arguments about what the wall will prevent are inflated or incorrect.

I’m not in a position to know whether the president believes his own rhetoric or whether he deliberately peddles nonsense because he assumes Americans won’t know better. But either way, the missives reinforce a couple of obvious, inescapable truths.

The first is pretty much every argument Trump has made in support of his goal has been wholly detached from reality.

As the number of attempted illegal border crossings drops to generational lows, Trump insists there’s a “crisis” that apparently only he can see. As the numbers point to visa violations as the principal explanation for illegal immigration, Trump pushes a wall that’s wholly unrelated to the underlying concern.

The president says a wall would keep out asylum-seekers, but that doesn’t make sense: under the existing system, these people either go directly to legal ports of entry, or they deliberately seek out Border Patrol officials after reaching American soil. He argues that a wall would stop the drug trade, but the Drug Enforcement Administration has said the opposite. Trump insists that to oppose a wall is to welcome crime, but there’s ample evidence that undocumented immigrants are less likely to break American laws than native citizens.

Trump has pointed to terrorists entering the United States through Mexico, but his claims appear to have been made up. He’s said illegal immigration costs the United States between $250 billion and $275 billion a year, but those numbers are made up, too.

The president added yesterday that Israel has a wall and it’s “99.9% effective.” Anne Applebaum highlighted the details he overlooked: “The ‘wall’ that separates Israel from the Palestinians in the West Bank and Gaza … isn’t a wall at all; it is a ‘multi layered composite obstacle’ composed of multiple fences, barricades and ditches that are constantly patrolled and monitored. Unless you are prepared to pay for all of that as well, a U.S.-Mexican border wall is pointless.”

Under the usual model for Trump, the president starts with the answer that sounds good, and then everyone around him works backwards to reverse engineer a policy blueprint that satisfies him. Except, in the case for the wall, this post-policy approach to governing has failed spectacularly: Trump World has spent years trying to come up with a sensible, substantive rationale for his dream, and the only thing we’ve heard are a series of easily discredited talking points.

How does the president respond to the factual details that prove his arguments wrong? By repeating the bogus claims anyway, as if fact-checks don’t exist.

And if the first problem with the pitch for the wall is that the arguments for it are baseless, the second problem is that the idea itself is kind of ridiculous. Vox’s Matt Yglesias explained today:

Obviously there’s nothing silly about the general idea of walls to separate pieces of territory. But if you’ve ever been to the US-Mexico border, chances are you’ve seen that there’s already lots of wall there. Significant swaths of the border are made up of transnational conurbations like San Diego-Tijuana or El Paso-Juarez, where, in the absence of imposing physical barriers, it would be very challenging for Border Patrol to stop people from sneaking across. What’s left are desolate, uninhabited stretches of border where construction logistics are difficult, crossing is difficult, and the Border Patrol’s detection work is relatively easy.

Anne Applebaum’s latest column added, “[T]his isn’t a debate about border policy. It’s a debate that tells us which of our politicians cares about the real world inhabited by real Americans and which prefer to live in a fantasy world created by the president’s imagination. For the future of the country, it’s important that reality wins.”

Based on everything we’ve heard from Donald Trump in recent years, his desire for a giant border wall seems to be largely based on a child-like logic. As he sees it, illegal immigration is a problem, immigrants can’t walk through walls, so if there’s a wall the problem will disappear.

For the sake of furloughed federal workers, the sooner policymakers look at this argument like adults, the better.