The reputation of libertarians is that they are selfish – and that female libertarians are especially selfish. After all, libertarians insist on applying commercial paradigms to moral problems, a habit that seems asocial, not to mention downright unfeminine. Typical would be Sally Satel, a doctor-scholar at the American Enterprise Institute in Washington. Satel has shown sympathy in print to vendors of human organs; she has also argued for tax credits for organ donations. Her buddy libertarian, the blogging diva Virginia Postrel, has a post up right now on her site mocking New York health authorities for denying restaurant chefs the right to prepare gourmet fish with a daring method that may be unsanitary. Where is this woman’s concern for infant infection?

It is intriguing then to find the pair engaged in the most altruistic and intimate of actions. Early this month on a Saturday at Washington Hospital Center, Virginia gave Sally a kidney. Though there is always the risk that Sally’s body rejects Virginia’s kidney, both women are recovering well. This kidney story is interesting both for itself and the light it sheds on political stereotype.

Late last summer, at age 49, Sally got the news that her kidneys had retired from life a few decades before she planned to. Sally faced a choice: a transplant or what she calls “the death sentence” of dialysis. A 1984 law, the National Organ Transplantation Act, named a single warm-hearted sounding entity, the United Network for Organ Sharing, as America’s public broker.

Yet some 90,000 people languish on the organ wait-list, and, Sally learned, the wait for kidneys can be years. The same Act outlaws the sale of organs, punishing sales with prison terms of up to five years. Satel’s parents have died and there was no family member who could supply her with a kidney. And officials from the American Society of Transplant Surgeons had spoken disapprovingly of private donations between unrelated parties. Social conservatives and President George Bush’s advisers too often frown on the idea of organ transactions. There was no easy legal way for Sally to get her kidney.

After a lifetime of hypothesizing that public monopolies do damage, Satel had come upon an all-too-personal example of how this was so. Energized, she wrote a column in the New York Times about the problem, noting that an average of 18 people died everyday waiting for organs. In a forthcoming article in the magazine Character, she quotes nephrologist Benjamin Hippen as noting that the supposedly humane set up “degenerates into an equal opportunity to die on the waiting list.”

Sally found a donor on the internet through “matchingdonors.com,” but the match fell through. This week she emailed me a happy description of what happened next: “Virginia heard of my health problem from a mutual friend in early Nov and contacted me saying that if the internet donor guy failed, that she would step up. And that is how she came to be!”

“We were friends, but not the knew-each-other all our lives spent every summer together kind,” Virginia, recuperating in Dallas, told me yesterday.

It turned out that Virginia’s kidney was a good match for Sally’s. They joke that they even had the same blood type: Diet Coke. Virginia’s website,”dynamist.com,” has a photo of Sally, post-op, with her favorite beverage.

Still, family, acquaintances and doctors alike urged the libertarian Virginia to think more selfishly about surgery. “I learned you have to be really bullheaded to give a kidney to a friend,” she says. The pair planned the surgery efficiently for a Saturday – it might have taken place on a Thursday, but Postrel’s husband, a professor who teaches business school, had to give a final exam that day. The hospital caseworker noticed that Sally received more flowers than other transplant cases. Libertarians, it turns out, have lots of friends.

But was this a policy kidney? In a certain sense, yes. As a fan of biotechnology, Virginia recalls, she didn’t have the “visceral” reaction that others might have to giving an organ. (Yes, she used that word). She looked up the risks of the donation and found that “we do lots of riskier things every day.”

After spending so much time thinking renally, Virginia’s husband Steven Postrel, even came up with an own elegant little market solution to the fatal organ shortage. Citizens who give an organ get a holiday from federal taxes for a year. High earners pay lots of tax, and low earners pay next to none, especially nowadays. As Postrel points out, philanthropists are more likely than the desperate tuition-short immigrants to take advantage of such a break. The holiday idea is therefore less vulnerable to the usual criticism that monetary reward invites exploitation of the poor.

Still, the Virginia-to-Sally transfer was at bottom altruistic, not political. “It was not as Virginia, the libertarian, but Virginia, the friend, that I was giving” Postrel says. “People who believe in markets do all sorts of non-market transactions.” Without thinking much about it, Postrel and Satel have made some important points. Well-intentioned policy can be fatal. Arch-conservatives can have big hearts, as big as any hearts on hard left or at the Democratic Leadership Council. Market-orientation and charity are not opposites. Sometimes they go together. Public institutions don’t have a monopoly on morality, and they probably shouldn’t have a monopoly on kidneys, either.

Miss Shlaes is a columnist for Bloomberg News.