President Biden has decided to end the war in Afghanistan. He feels it’s time, and so do a lot of Americans.

I feel it too. I’m just not sure feelings should win the day.

In his televised address announcing the decision, Mr. Biden reiterated that American withdrawal can’t be “tied to conditions on the ground” because no one can say what conditions must be met in order to depart.

As a senior administration official explained to reporters, “This is not conditions-based. The president has judged that a conditions-based approach, which has been the approach of the past two decades, is a recipe for staying in Afghanistan forever.”

Let’s be clear: “not conditions-based” is another way of saying “unconditional.”

But what if the problem isn’t with the answers and rather with the questions?

We have police, firefighters and paramedics. No one outside the “defund the police” crowd would say, “We have to get rid of them because no one can describe what the conditions would look like when we wouldn’t need them anymore.” “How does this end?” is the wrong question because there will always be crime, fires and medical emergencies. We don’t dismantle dams because we can’t imagine a scenario when they’ll no longer be necessary. We do dismantle them when they’re no longer needed.

Before you take this analogy and go where I do not intend, I’m not saying we should be the “world’s policeman.” We’re not and can’t be. Indeed, terrible things are happening right now in all sorts of places — Myanmar, Tibet, Hong Kong, Ukraine, parts of Africa, etc. — and we’re not sending in our globalist gendarmerie to stop it. But we are in Afghanistan, not to police the world, or even Afghanistan. We’re there to ensure that the Taliban doesn’t take over the country and make it a safe haven for terrorism again.

Some argue that our presence isn’t needed. I don’t find the arguments persuasive, in part because if that were true, why say conditions on the ground don’t matter? Why not say, “We’ve met the necessary conditions.”

That the White House won’t or can’t make that case tells you that the determinative condition for withdrawal isn’t in Afghanistan, but in America. And that condition is exhaustion.

“I wouldn’t say enough is enough,” retired Gen. Colin Powell, who was secretary of state when we invaded Afghanistan in 2001, told The Washington Post. “I’d say we’ve done all we can do.”

The Soviet Union, which occupied Afghanistan until early 1989, “did it the same way,” Mr. Powell added. “They got tired, and they marched out and back home. How long did anybody remember that?”

Put aside the shabby moral equivalence — we’re not in Afghanistan to build an empire. The lesson of Soviet withdrawal has nothing to do with how long people remembered it — which was quite a while, by the way — but with what happened after.

There’s a robust debate among scholars about how much the Soviet war in Afghanistan led to the demise of the Soviet Union. There’s no debate that Soviet defeat led to the rise of the Taliban and al-Qaida. “The myth of the superpower was destroyed not only in my mind but also in the minds of all Muslims,” Osama bin Laden recalled about the Afghan victory. “Slumber and fatigue vanished.”

The idea that our departure, pegged to the 20th anniversary of al-Qaida’s successful attack on America, won’t be seen as a defeat for the United States by the Taliban and other Islamists is preposterous. (Of all the aspects of Mr. Biden’s decision, picking Sept. 11 as the deadline is the most baffling.)

The White House insists that the American-backed Kabul government can hold back the Taliban on its own and that we will still be able to conduct operations against terrorist safe havens with drones or other assets based outside of Afghanistan. This is dubious. So is the claim that the administration can use diplomatic pressure and sanctions to keep the Taliban from once again murdering heretics and brutalizing women and girls. If 20 years of war couldn’t do it, banning travel and freezing bank accounts seem unlikely to be more effective.

Again, I feel the exhaustion too. And I sincerely hope Mr. Biden is right. But feelings and hope aren’t arguments. The more likely scenario is that a civil war will come soon, Kabul will fall with Saigon-like rapidity and horror, and this president or the next will have a worse problem to contend with than maintaining a token force that has kept the Taliban at bay for 20 long years.

Jonah Goldberg is editor-in-chief of The Dispatch and the host of The Remnant podcast. His Twitter handle is @JonahDispatch.