The article makes a reasonable case that McCollum suffers from Asperger's Syndrome, a mild form of autism that leads to intense fixations on particular subjects. Compared with typical Asperger's sufferers, McCollum is lucky: his particular obsession corresponds very neatly to a perfectly legitimate profession. He fits in perfectly well with "real" subway workers, many of whom know him, are glad to see him and work with him, and actively collaborate with his infiltration mission -- the professional context, apparently, negates the social awkwardness typically associated with Asperger's.

In another sense, though, McCollum is very unlucky in his fixation, precisely because it leads him out into the world, into a place where he's not technically allowed to be. He doesn't work for the Transit Authority, and when they catch him in one of their vests, carrying one of their badges, and checking the brakes on one of their subway cars, they press charges.

So wait a minute. Why are they pressing charges? Why don't they just give him a job? Nowhere in the Harper's article is this question really addressed. It's not like Darius McCollum is obsessed with the subway; he's obsessed with working on the subway, and he certainly seems to be good at it. Part of the subtext in the article was that many of his "colleagues" are so glad to see him because he's perfectly capable of working alongside them and easing their own workload. If anything, he's the ideal employee: totally selfless, perfectly knowledgeable, and utterly dedicated.

At this point, there's probably a vicious circle at work. He's got a criminal record and a long history of superficially shady involvement with the subway system. Those who know McCollum like and trust him, but the MTA has got to be worrying about what will happen if something ever goes wrong while he's nearby.

If a criminal court is willing to throw him in the slammer (for making a good-faith by-the-book attempt to get a stalled train moving again), maybe a civil court would look skeptically at turning such a man loose on the subway system. If the MTA ever gets sued for an incident he has any connection to, they're going to look pretty bad in the face of questioning from a hostile ambulance-chaser.

I can see it now. "Mrs. Wiggum, when you boarded that train, who did you think would be maintaining the switches on the track? Did you expect that it would be a trained and qualified MTA employee? Or did you think that it would be a mentally ill man off the streets, a man with no training and no certification, a man with an unhealthy obsession with the subway system, who sneaks down into the tunnels wearing a stolen uniform so he can satisfy his obession by playing at being an MTA employee, a man who has been repeatedly arrested and convicted for endangering the safety of passengers with his antics? I see. Thank you. Your witness."

It's a gross distortion to put things like this, but there is a kernel of an important idea in that harangue. The Mrs. Wiggums of this world think about subway maintainance, if they think about it at all, only rarely and distantly. They make a loose assumption that everything is being done according to well-defined procedures by largely interchangeable but more or less competent professionals. They don't want to think about the qualifications of the indviduals doing that maintainance; they don't want to have to evaluate the risks of boarding a subway based on how much they trust Darius McCollum.

And in a division-of-labor capitalist society, they don't have to. That's the idea behind McDonalds. That's the idea behind accounting regulations. That's the idea behind the EPA, the FAA, the FDA, and OSHA. It's the idea behind the assembly line, one-click ordering, Six Sigma quality control, and sweatshop labor. And it's the idea behind throwing people in jail if they impersonate your employees. The product or service must be completely isolable from any possible irregularities in its creation.

That way, people can consume it and forget about it, and they don't need to tie up their social neurons interacting with Pablo, who sewed the seams in their shirt for a nickel an hour, or with Tim, who loaded their books into a box at the Amazon distribution center, or with Darius, who checked the electrical relays on the switches at 40th Street.

That's how large societies generally work. Not everyone knows everyone else. You vouch for the people you know; as for the rest, you set up powerful institutions -- the police, the SEC, Human Resources departments, corporations, whip-bearing overseers, or the MTA -- to keep them in line. That's the choice Mrs. Wiggum made. That's the choice we've all made. We ask society to simplify things for us.

And that's the choice that keeps Darius McCollum behind bars. It may be perfectly true that he poses no threat to others, but it's also equally true that his particular situation is complex, more complex than the NYCTA wants to deal with. They're not in the business of dealing with complex issues; they're in the business of making the trains run on time, of reducing the tangled lives of thousands of trainmen and maintainance workers into an orderly grid of on-time statistics.

From the standpoint of that grid, Darius McCollum is a rounding error. Putting kind, competent, and harmless people in prison is the sort of error that passes for typical in this country.