IT WAS THE day before Thanksgiving and Paul Wagner was on his lunch break, reading the paper. He worked as a purchasing manager at Peirce-Phelps, in Philadelphia, a wholesale distributor of heating and air-conditioning products. He was 40 years old and lived with his partner, Aaron, in a small apartment. He was pale and slightly built. He smoked and had a smoker’s porous skin. His mother had died six months before, in her late 50s, of sarcoidosis. They had not had a good relationship, but her death had affected him quite deeply.

Wagner considered himself a “dry person”—curt, moody, sometimes rude.

He believed that, to people who didn’t know him, he came off as an unsentimental type, possibly even a bit mean, though in fact he was not like that at all. He owned two cats and two elderly cocker spaniels that he had rescued from a shelter. He ran the United Way fundraising campaign at work for three years and organized food drives for local soup kitchens. He regarded these acts not as virtuous but as duties. He believed that if his needs were met and he found himself in possession of a surplus—of money or time or wherewithal—he was obliged to share it. Share it, not give it all away: He liked nice things—he wasn’t going to become Amish. But it was very, very important to him that when he met his Maker he could say that he gave more than he took.

Reading the paper, Wagner noticed an article that described a website named, where people who needed a kidney transplant could post a message describing themselves and their situation, perhaps appending a photograph. The hope was that a stranger would see the posting and be moved to donate. Wagner typed the name of the website into his computer. He clicked on the “search patients” box and typed in “Philadelphia.” The first patient he saw was Gail Tomas. He enlarged her photograph on his screen so that he could examine every detail. She was a woman of mixed race in her late 60s. He stared at her, searching for clues to her personality in her hairstyle and how she wore makeup. Almost immediately, he felt that she was the one. He knew that his blood and her blood would match and that he would donate a kidney to her.

He went home and told his partner, “Aaron, there’s this lady I read about that’s going to die if she doesn’t get a new kidney and I’ve decided to give one to her.” Aaron said no. Wagner told him sorry, but he was going to do it anyway. Talking to his father was more difficult. Some years before, his father’s second wife had had kidney disease. Wagner had offered to donate to her, but she and his father had felt that it was against their principles to ask so much of a person, even a son. So they refused his offer, and, waiting for a cadaver kidney, she died.

Wagner assumed that he and Tomas would not become friends after the surgery. He had given the matter some thought. How could they possibly have a healthy relationship, he reasoned. It would be bad for her to feel beholden to him, and it would be bad for him to have her believing that he was some kind of saint. The whole thing would just be way too freighted and creepy and was better avoided. Tomas, however, had other ideas.

Tomas was a retired opera singer. If Wagner was dry, she was the opposite—vivacious, chatty, candidly emotional. For her, their first meeting, in the hospital waiting room, was wonderful: She felt that they’d known each other all their lives.

Wagner managed to be friendly when Tomas introduced herself, but he was all churned up afterward. He didn’t know what to make of this exuberant lady he was giving his kidney to; he couldn’t figure out what emotions he should allow himself to experience. His mother had died less than a year before, and now here he was potentially entangling himself with another very sick older woman, and what did that mean? Donating a kidney to find yourself a new mother, what could be more obviously twisted than that? He was also worried that he’d done a bad thing by allowing himself to meet Tomas at all. It made him feel guilty. Did it diminish the value of his deed to accept her gratitude?  Wouldn’t he be a better person if he hadn’t met her and had received no thanks? Had his donation now become just a matter of gratifying his ego?

The transplant surgeon was puzzled by Wagner. He wasn’t sure that he was willing to do the surgery—he was concerned that it might be a violation of his Hippocratic oath to operate on a healthy person who wasn’t even related to the recipient. They met and talked for more than an hour. Near the end of the conversation, Wagner was astonished to see that the surgeon was crying.

Doctors tend to be deeply suspicious of altruistic donors. Especially in the early days of kidney transplants, in the late ’60s and early ’70s, many doctors saw altruistic donation through the lens of psychoanalysis, and, viewed thus, it looked troubling indeed. What was “altruism,” after all? A motive so much in conflict with primary instinct had to represent some kind of pathology. Was it masochism? Unresolved guilt? Donating an organ to a stranger was not just not admirable, doctors felt—it was perverse, it offended the conscience. It was against human nature. Surgeons and psychiatrists went to heroic lengths to draw out the conflicts and ambivalence that lay hidden beneath donors’ supposed willingness to undergo surgery.

Even the recipients of organs were ambivalent. One man was so overcome by a feeling of obligation toward his donor sister that he couldn’t stand to look at her. A son refused a kidney from his mother because, he told his surgeon, “She’s devoured enough of me already.” The force of gratitude could be dreadful with the gift of an organ, when no thanks seemed adequate and reciprocation was impossible. Doctors began to realize that to transplant an organ was to stir up the muck of familial emotions, with consequences that could not be predicted. Donation tended to bind the donor and the recipient together, sometimes with love, sometimes with guilt, or gratitude, or a feeling of physical union due to the presence of the organ of one in the other’s body. The strength of these new bonds could weaken other bonds and leave families strained and distorted. If a person donated to a sibling, for instance, might he not become too close to that sibling, at the expense of his relationship with his spouse? One transplant physician believed that, after a sister donated to her brother, the sister “felt absolute control over her brother, as if she had castrated him.” After the surgery, instead of going home to his wife and children, he moved into his sister’s house to recover.

Transplants have become more commonplace, and attitudes toward donation of organs have become somewhat less fraught. Potential donors register on almost every day. Either through MatchingDonors or through a hospital, about 600 have gone through with surgery. But the change in attitude is mourned by those who feel that it signals an encroaching spiritual callousness. To the ethicist Gilbert Meilaender, for instance, the reluctance that many feel toward donating organs, even after death, is not selfishness or superstition but a sign that our sense of the body as something whole, something human, something sacred, has not yet withered. A society in which everyone in cheerful rationality signed his donor card without a qualm would be, to Meilaender, a horror. The giving of an organ, by the living or the dead, should not be purged of anguish. For him, the tyranny of gratitude is not a perversion of love but the prototype of love: the bond between parents and children.

AFTER THE SURGERY, Wagner started feeling very sad all the time. He admitted to himself that it was difficult to come down off the high of being a hero. Worse, Tomas had suddenly stopped returning his phone calls. Was she angry with him? he wondered. Looking for advice, he started posting on a website, Living Donors Online, and he discovered that many donors had to deal with peculiar emotions after surgery. He read about one case in which a woman had donated to her sister, but the kidney was rejected and her sister died; after that, the rest of the family stopped speaking to her. One spouse donated to the other, then the recipient spouse left the donor, perhaps because the burden of gratitude had left the marriage irredeemably distorted. That had happened quite a few times, it seemed.

Finally, worried, Wagner started calling hospitals, and he found Tomas. She’d been very sick and hadn’t wanted to scare him, but now she was better, and she wanted Wagner in her life. Still smarting, he wasn’t sure. She invited him to her son’s wedding. He declined, several times, until finally she got angry and yelled at him, and that, somehow, for Wagner, made everything all right. If she could yell at him, then he was not always perfect in her eyes and they could have a normal friendship. She wasn’t his mother, he knew that; it would be fine. In fact, Tomas did consider herself his mother, more or less. She wanted him at her house on holidays, she hounded him about smoking and taking his blood-pressure medication. But it was fine anyway.

So what do you make of Paul Wagner? Do you find the idea of donating a kidney to a stranger noble? Or freakish? If the latter, is it the extremity of the act that baffles you? Does it seem crazy, giving something that precious to someone for whom you have no feeling, and whom, if you knew him, you might actually dislike?

Perhaps it’s not quite as crazy as it sounds. Kidneys are now often extracted laparoscopically, which leaves only tiny scars. A donor usually feels normal again in two to four weeks, the remaining kidney growing to compensate. And the risk of complications is low. If a person gets kidney disease, it affects both kidneys, so as far as that goes, a donor is not giving away his spare (though a spare kidney is useful if the other is damaged in a car accident, say, or if a person develops kidney cancer). Still, the carnality of the act, the violation of the body, stops people. Its moral logic seems, to some, inhumanly rational, suicidally so: If we’re going to start thinking of bodies as repositories of spare parts for other people, why not donate all our organs and save many lives?

Most people find it uncomplicatedly admirable when a person risks his life to rescue a stranger from fire, or from drowning. What, then, is it about saving a stranger by giving a kidney, a far lesser risk, that people find so odd? Do they feel there is something aggressive about the act, as though the donor were implicitly rebuking them for not doing it, too? (There is no rebuke in saving a stranger from drowning—you weren’t there, you couldn’t have done it. And you can always imagine that you would have if you had been.) Or perhaps it’s that organ donation, unlike rescue, is conceived in cold blood, and coldblooded altruism seems nearly as sinister as coldblooded malevolence.

From a story originally published in The New Yorker. ©2009 by Larissa MacFarquhar. Used with permission. All rights reserved.