The sidewalks of north Park Slope must be among the narrowest and most uneven in Brooklyn. They crash against the stoops of landmarked brownstones and split over the roots of oak and sycamore trees, menacing the ankles of pedestrians. Baby strollers compete for space with dogs of all sizes, shoals of high-school students, and shopping carts from the Park Slope Food Co-op. Here comes one now, rattling catastrophically, like Max Roach whaling on the high hat. It’s pushed by a Co-op member, who is accompanied by another, in an orange crossing-guard vest: a walker, in Co-op parlance, who will return the cart after the shopper has unloaded her groceries at her house or her car, or hauled them into the Grand Army Plaza subway station. It is against one of the Co-op’s many rules for the shopper to have the walker do the pushing; that’s the shopper’s responsibility. It is also against the rules to drag a walker beyond the Co-op’s strict walking bounds, though some members, when they have escaped the reach of the institutional eye, will try to get away with murder. The noblest aspirations of civilized society versus the base reality of human nature is a theme that frequently comes up at the Park Slope Food Co-op.

The Co-op opened in 1973, in a room of the Mongoose Community Center, a leftist hangout on the second floor of 782 Union Street. There were no shopping carts. There were stairs, which members descended perilously, clutching boxes laden with peaches and tomatoes and other produce from Hunts Point, the wholesale market in the Bronx. For years, even after the Co-op took over the building and expanded its offerings to things like toilet paper and batteries, members kept lugging boxes around the store. But the carts, when they came, were not greeted with universal relief; one member wrote to the Linewaiters’ Gazette, the Co-op’s biweekly newspaper, to complain that they were turning the Co-op into “a suburban, John Sununu nightmare.”

Terminology is important at the Co-op. Sometimes on the building’s intercom system—available to everyone for paging out requests, announcements, or complaints—someone will make the mistake of using the word “customer,” and invariably someone else will page right back to point out that there is no such thing as a customer here. “Shopper” and “member” are all right, and so are “shopping member,” “member-worker,” and “member-owner.” Everyone who can afford it pays a twenty-five-dollar joining fee, plus an “investment” of a hundred bucks, returned upon leaving, and everyone works. The place runs on sweat equity: your blood for bread, your labor for lox.

In the late eighties, the Co-op had seventeen hundred members. Today, there are more than seventeen thousand, which makes it the biggest food coöperative run on member labor in the country, and, most likely, the world. Members unload delivery trucks and stock shelves. They ring up groceries, count cash, scrub toilets, and sweep the floor. They scan other members’ I.D. cards to admit them into the building, and they look after other members’ kids in the child-care room. In the basement, members with colorful kerchiefs tied around their heads bag nuts and spices, price cuts of meat, and chisel blocks of cheese. Bent over their walnuts and dried-apple rounds, they bear an unmistakable resemblance to Russian factory workers, one point in favor of Co-op critics who like to compare the operation to a Soviet work camp.

Upstairs, members answer the phones, speaking to other members who call to explain why they’re missing a shift, or to beg for an extension to make up the shifts they have already missed. With some exceptions (the milk-and-honey land of retirement is a distant possibility), members must work a shift of two hours and forty-five minutes every four weeks—not every month, because, as Joe Holtz, a co-founder of the Co-op and a longtime general manager, says, “months are notoriously not into equality.”

The place is always packed, though membership numbers are in constant flux, because, in addition to coming in, people go out. They take parental or sick leave, or fall so far behind on work shifts that they skulk away to Whole Foods and Trader Joe’s. They move to faraway neighborhoods or out of state, though even this is not enough to keep some people away. A few weeks ago, a member working at a checkout counter was ringing up an array of cucumbers, separating the Kirbys from the Persians. She was Claire Oberman, a tax preparer who lived in Brooklyn until she moved to Bridgeport, Connecticut. Connecticut! She takes the train in once a month to do her shift.

“It’s like coming home,” a member working next to her said.

It was August, and the Co-op was in a relaxed mood. “Grazing in the Grass” was playing on the speaker system. A middle-aged guy in a “Make America Read Again” T-shirt examined containers of ice cream. A small, sunny woman wearing a baseball cap that said “Life Is Good” was working the exit, highlighting the “PAID IN FULL” line on members’ receipts before sending them on their way. Like any other store, the Co-op has problems with theft. At one point, an elevated chair was installed so that a member could sit and surveil the shopping floor, like a lifeguard or a tennis referee. Members found this unfriendly. Then checkout workers were instructed to do random bag inspections. Members found this racist. The highlighter system is the best method that has been arrived at so far.

Some Co-op members stick AirPods in their ears to get through their shifts, but others have a philosophy about the work. The woman in the “Life Is Good” hat had a philosophy. She made contact with each person who came her way, putting out positive vibes. “Hi, sis, how you holding up?” she said. “Your mind is somewhere else. Come on back. Enjoy this moment! Life is a journey, and we forget sometimes about our blessings.” She pointed to her cap. “People come through here all the time so stressed out. Why are you so stressed out? If you can’t handle it today, let it go. Put it on the shelf, come back tomorrow. It’ll be here.”

A cloud of notoriety and Schadenfreude surrounds the Co-op in a way that does not seem entirely fitting for a grocery store. When non-Co-op people think of the Co-op, they picture snobs and brats, self-righteous foodies, hypocritical hippies, bougie mothers who have their nannies do their shifts, adult professionals who melt down like tetchy toddlers when kale is out of stock. The Times, which tends to treat the Co-op like a rogue nation-state, has covered the hummus wars, the pension controversy, the rumor that Adrian Grenier was kicked out—strenuously denied by the actor. “These are the self-important twits who are running our society today!” a commenter wrote in response to a 2012 article about a contentious Co-op meeting.

Members’ own views on the place vary. “It’s a user-friendly way of experiencing the pitfalls of communism,” a friend and former member told me.

“I have no hard feelings,” another friend, who was slowly working her way back from a suspension, said. “My hard feelings are about myself.”