No one in his right mind today would willingly submit to the medical ministrations of Moses Maimonides, the great 12th-century Jewish doctor and philosopher. Maimonides, very much a man of the medieval world, possessed a medical wisdom that was little more than a mix of herbs and hokum, borrowed from the ancient Greeks. At best, it might meet the basic ethical dictum to do no harm.

Yet Maimonides remains almost a saint among doctors, a medieval Albert Schweitzer, a Jewish Hippocrates. Hospitals around the world bear his name and Jewish doctors still gather together in Maimonides Societies in almost every American city. And as Yale surgeon and best-selling author Sherwin Nuland points out in a new book, many Jews still feel a deep affinity for the man they know by an acronym of his Hebrew name, "the Rambam."

Nuland, author of the 1994 "How We Die," begins his new "Maimonides" with a discussion of an intriguing question: "Why is it, in fact, that so many Jews have become doctors?" And why do so many of them, and so many Jews who haven't read a word of Maimonides' abstruse texts, revere the old doctor and religious leader as a living presence in Jewish cultural life? Nuland, whose book is part of a new series devoted to Jewish literacy published by Schocken and Nextbook, locates the answer in some basic trends in Jewish history, trends that Maimonides epitomized.

For Jews, medicine was a portable profession during long centuries of persecution and migration. It was also a natural extension of a tradition of learning. Maimonides, born in Spain in 1135 to a bookish father, was buffeted by intolerance and fled across the Mediterranean world before settling in Fustat, Egypt (near Cairo) in 1168. There, he emerged as the spiritual leader of Egyptian Jews but scrupulously refused to take payment for his religious services. So even as his name was spreading to the ends of the medieval world, he turned to medicine to make ends meet. Such was his intellectual gift, and personal appeal, that he was soon made physician to the court of the Muslim sultan of Egypt.

Although the Jews, writes Nuland, never created a specifically "Jewish" medicine, as the Chinese created a Chinese medicine, they associated healing with basic religious duty.

"One who is ill has not only the right but also the duty to seek medical aid," wrote Maimonides, because, he argued, we maintain the body to support our spiritual quest to know God. Christians, on the other hand, attributed disease to supernatural causes, and through the example of Jesus and the martyrs, they placed redemptive value on suffering, Nuland argues. The Jews found that nonsense and focused on healing as a religious calling -- which gave medicine a special status and urgency within Jewish culture. Medicine, for them, was a calling, and perhaps for that reason they were renowned (even among Christians) for being very good at it.

"That kind of thinking has so suffused medical thinking in a large extent because of Maimonides," Nuland said in a recent interview, while visiting Washington from his home in Connecticut. The notion that medicine is more than just a job or a career, that it brings with it a deeper moral obligation, is no longer a specifically Jewish attribute of medicine, he said, but it is one of the Jews' great contributions to the field.

Nuland comes to an interest in Maimonides not only as a Jew -- he grew up in a Yiddish-speaking, Orthodox house in New York -- and a doctor but also as a historian of medicine. His new book is the second in Schocken's Jewish Encounters series (the first, by poet Robert Pinsky, is devoted to King David; the next up is a biography of the boxer Barney Ross). Jonathan Rosen, editor of the series, said it was a natural to call on Nuland for this volume.

Rosen said he decided on Nuland even before he knew the celebrated Yale professor -- a trim, articulate man in his seventies -- was born Shepsel Nudelman. Rosen was looking for an author who could connect with Maimonides not just philosophically. He wanted someone who "could swim across this gulf of 800 years and find if Maimonides has something to say to him. Do they speak the same language?"

Other writers have taken up the many intellectual challenges thrown down by Maimonides' life-long effort to make Jewish law and learning as intellectually orderly and convincing as ancient Greek philosophy. But Nuland connects with a more emotional Maimonides, a human figure with familiar frailties and feelings. Although it's easier to construct a picture of Maimonides' intellectual life, there are fewer clues with which to limn his personal character. We know, for instance, that when Maimonides' beloved brother David died in a shipwreck, Moses was disconsolate. He went into a dark depression for nearly a year. Later, he would write, "Eight years have since passed, and I still mourn, for there is no consolation. What can console me? He grew up on my knees; he was my brother, my pupil."

"His description of clinical depression could be in a modern psychiatry textbook," Nuland told an audience earlier this month at the Jewish Community Center.

Nuland also marshals evidence from a letter written in 1199, when the philosopher, then in his sixties, was at the pinnacle of his power and responsibility. Writing in response to a translator who sought to visit and work with him, Maimonides strongly discouraged the visit, saying he had no time to spare. And then he laid out the shape of his day: He traveled to Cairo and back again, a mile and a half each day, to attend to his court duties; he ate only one meal in 24 hours; and even at home he found himself swamped with suppliants, patients and the practical duties of leadership. "Patients go in and out until nightfall, and sometimes even I solemnly assure you, until two hours and more into the night," he wrote. "I converse and prescribe for them while lying down from sheer fatigue, and when night falls, I am so exhausted that I can scarcely think."

That dedication clearly appeals to Nuland, who has himself been astonishingly productive despite many claims on his time.

"One can identify with him, as a contemporary physician," he says. It's not just the sense of commitment and calling but also Maimonides' attention to observation, and the particulars of each patient. "There is this sense that he is talking to another doctor, or patient, in this almost warm, conversational, avuncular way. It is a very reassuring kind of thing."

Sorting through Maimonides' medical advice, Nuland finds a few things that might have worked, and a lot of concoctions that would, at best, have had a placebo effect. Zinc oxide, he says, was recommended for hemorrhoids and is still used today.

"You do find things," he says. "Doctors have always been pragmatists, and even though the theory of medicine may have been bonkers, they did what in their hands seemed to work. Maybe it worked because it was going to get better anyway."

Maimonides wrote widely on medicine, building on the medical lore first compiled by Galen. A Greek from the 2nd century, Galen believed that the body was composed of "humors," blood, yellow bile, black bile and phlegm; that illness was caused by their imbalance; and that healing was a matter of recalibrating their equilibrium. Nuland calls Galen "the most influential physician who has ever lived," which does not mean that he was the best physician who ever lived. In the spirit of Galen, though with a pragmatic eye trained on individual patients, Maimonides wrote 10 books on medicine, including volumes devoted to asthma, sexual intercourse and an extensive glossary of drug names.

But the bulk of his writing dealt not with the body and its ills but with the soul and the religious laws that govern humankind's existence. Nuland also deals with those texts, arguing that Maimonides' great strength was as an organizer and clarifier of complex tradition. He sorted through and codified and made accessible a huge bulk of Talmudic writing, offering the Jews (rather arrogantly, critics have said) a Cliffs Notes to the arcane accretion of spiritual writing that had gathered over the millenniums. Of one of Maimonides' most magisterial works, the Mishneh Torah, Nuland writes: "Maimonides was writing what many have called a constitution for the Jewish state he envisioned as being on the horizon."

And there is the "Guide for the Perplexed," the book best known to readers who aren't particularly interested in Jewish law but one of the most complex philosophical works in the canon nonetheless. It was a discussion of the "Guide" at the Jewish Community Center that brought Nuland to Washington this month, and it is discussion of the "Guide" over the past 1,000 years that has given Maimonides the aura of a mystical genius.

Throughout his life, Maimonides was preoccupied with the clarity and authority of Aristotle's thought. The "Guide" remains the most ambitious Jewish effort to reconcile the adamantine laws of Moses with Aristotle's supple but rigorously consistent understanding of morality, the universe and the vexing question of where all this stuff that surrounds us came from. Reconciling Scripture with Aristotle is roughly analogous with reconciling the Bible with evolution, the fossil record, modern astronomy and the Enlightenment, except that men of Maimonides' era didn't compartmentalize and couldn't fall back on intellectually spongy ideas that put the truth of God in one category and the truth of science in another. For Maimonides, the effort required a careful look at every ambiguous Hebrew word; subtle new distinctions when he seemed to arrive at apparent contradiction; and the discipline, in a superstitious age, to allow religion to be the last word only after all other options had been exhausted.

Leon Wieseltier, literary editor of the New Republic and a longtime student of Maimonides who shared the stage with Nuland at the Jewish Community Center, argued that Maimonides is radical because he treated spiritual truths and scientific truths with the same skepticism and demand for logic and certainty. And indeed, the "Guide" is filled with chapters that classify religious law with the same rigor as a botanist classifying the plant world, and Maimonides gives methodical explanations for the ultimate purpose of seemingly arbitrary religious dictates. Why do Jews circumcise boys? "I think one of its objects is to limit sexual intercourse," wrote the author of the "Guide," reasoning that anything that curtailed pleasure would help bring randy men to heel. Why do Jews sacrifice lambs, goats and cows? "These species are animals which can be got very easily, contrary to the practice of idolaters that sacrifice lions, bears, and wild beasts."

Regardless of what one makes of Maimonides' particular explanations or arguments, the fact that he made them, that he looked at religious law as something as open to question and justification as philosophical or scientific truth, defines him as a heroic figure for rationalists such as Wieseltier.

"People who are opposed to the idea that beliefs must be justified are very threatened by him," said Wieseltier.

Nuland, who has said that each generation tends to create the Maimonides it needs, focused on a different aspect of the Rambam's legacy. As a reviewer in Commentary said, in praising Nuland's book, "The biographer lyrically fuses his own values with those of his subject" -- and for Nuland those values are the values of the physician. So as Nuland and Wieseltier discussed Maimonides' long and productive life, two different Maimonideses seemed to emerge. Nuland underscored the inspirational aspects, the sense of Maimonides as "a friend" and "someone who could walk the earth today." And Wieseltier seemed to admire the trenchant intellectual courage of one of the most "arrogant" rabbis that ever lived.

But it was more a question of emphasis than a radically different understanding.

Though Nuland clearly sympathizes with the humane qualities of Maimonides the doctor, his book places Maimonides' philosophical endeavors on a continuum with his medical efforts. Before his talk on the "Guide," Nuland suggested that there is a link between the two Maimonideses. The Rambam, he argues, was concerned not just with the health of the individual body but also with the larger health -- physical and spiritual -- of the Jewish people.

"My idea is that he considered the real purpose of his life to keep the Jewish people together," Nuland said. "The focus of his life was keeping that religion together, and also bringing it into the next centuries."

Moses Maimonides: "One can identify with him, as a contemporary physician," says author Sherwin Nuland.In his book about Maimonides, Yale surgeon Sherwin Nuland notes that Jews in the 12th-century physician's time viewed healing as a basic religious duty.