Monday afternoon, a black man named Jordan Neely died in a subway car following a struggle with other passengers.

Press reports present these details: Neely had an untreated serious mental illness, he had not assaulted anyone but was displaying a threatening manner, the man who subdued him with a chokehold was white and had a military background, and Neely had a long involvement with the criminal justice system.

Further facts may be forthcoming, particularly if Manhattan District Attorney Alvin Bragg decides to press charges against Neely’s subduer.

But some essential details we may never know.

For example, we may never know what kind of involvement Neely had with health and human services systems.

Criminal-justice reformers might point out, correctly, that Neely’s many past arrests did not stabilize him.

But nor did whatever contact he may have had with homeless-outreach teams, social workers, safe-haven shelters, and outpatient clinics.

There are no equivalents of “inmate finder” websites for social programs.

Details about Neely’s involvement with health systems and social services could help inform policymakers about how best to design programs to head off the next “preventable tragedy.”

Did any past intervention work, at least temporarily?

When “service-resistant” seriously mentally ill people spurn initial offers of treatment, how much of an effort is made, on the part of city bureaucrats and nonprofit social services contractors, to re-engage?

The debate over crisis response concerns how to deal with situations like this one.

Many people with a military or law-enforcement background are disposed to rush in, to intervene.

As illustrated by the contrast between the responses to the March 2023 Nashville school shooting and the May 2022 Uvalde school shooting, a disposition to act quickly can sometimes make all the difference in resolving a crisis effectively.

It’s also true, however, that containment can be the sounder approach when dealing with the mentally ill.

Some situations (at home) will be more manageable in this way than others (in a public setting).

Distinguishing between containable and uncontainable crises can require split-second judgments.

Rushing in is not the way of the typical civilian “straphanger.”

This detail of the Neely tragedy is unrepresentative.

Some New York boosters celebrate the packed subway car — in which financiers, immigrant laborers, college students, Orthodox Jews, and charter-school kids all sit cheek-by-jowl — as a testament to the city’s success with diversity.

But scenes like that also recall the sentiment of Robert Frost’s “Mending Wall”: “Good fences make good neighbors.”

No one’s attacking anyone, but nor is anyone communicating or even acknowledging another’s existence.

In such close quarters, the only way that diversity can work is for everyone to keep his distance from everyone else.

As for disorder — someone screaming, say, or wildly gesticulating — you’re generally expected either to endure it or rely on public authorities to handle it.

The Neely tragedy was preventable insofar as it wouldn’t have happened if he had been in treatment, which was not the case, according to his family.

This detail also makes his a representative tragedy.

His aunt told The Post: “The whole system just failed him. He fell through the cracks of the system.”

Observations like that can be found in the coverage of practically every mental illness-related death.

The Neely case shows that Mayor Eric Adams’ involuntary treatment plan, launched in November, has yet to bring stability to the subways; at the same time, the case demonstrates the need for something like Adams’ plan.

Would anything proposed by the mayor’s civil liberties critics have prevented what happened?

Again, conveniently for the critics, we will likely never know, due to privacy law and the nonprofit sector’s opacity.

Sadly, this story’s most typical detail may be local progressives’ racially divisive rhetoric about it — describing Neely’s death, for example, as a “lynching.”

There’s always a possibility that incidents like these can advance the cause of substantive mental-health reform. 

It’s happened at least once before, and mental-health reform sometimes shows signs of enjoying bipartisan support.

Admittedly, it’s a slim possibility.

And it’s made even slimmer when racial rhetoric diverts public attention away from the far more constructive focus on untreated serious mental illness.

Stephen Eide is the author of “Homelessness in America,” a senior fellow at the Manhattan Institute, and contributing editor of City Journal, where this piece first appeared.