For lovers, the story of Abelard and Heloise is a constant reminder that love is a dangerous thing, and that a couple is, as the old saw runs, “a nation of two.” You’d think that the example of Abelard and Heloise (just one of many examples of dangerous lovers and their dangerous loves) would keep couples on the straight and narrow; and maybe it does, but not without a certain frisson that keeps the story alive after 800 years.

To refresh your memory, recall that Abelard was the greatest philosopher of his day. He hailed from Brittany and went to Paris around 1100, ostensibly to teach, but really to argue. If, as the popular imagination has it, Heloise had a body made for love (which, by contemporary accounts, she did), Abelard’s was made for arguing. He was short but wiry, as sinuous as his famed rhetoric. As James Burge demonstrates in his superb biography of a love affair, Abelard quickly conquered his foes in medieval logic and established himself as the philosopher du jour. For a while, he was in the camp of the politically empowered, and it was doing this period that he met Heloise.

Heloise’s uncle, Cannon Fulbert, hired Abelard to tutor his ward in philosophy. She was in her early twenties, and he around thirty-six. Heloise was apparently captivated by Abelard’s songwriting ability; his tunesmithing seemed to have caused many a heart to throb. Abelard, in turn, was knocked out not only by the young woman's nubility but her capacious, searching mind as well. They consummated their relationship, and carried on as lovers—luckily for us, extremely literary lovers, always exchanging notes—for about two years.

Nature always bats last: Heloise became pregnant. Along with the hormones, all hell broke loose. Bastardy wasn’t the problem: being born out of wedlock wasn’t the stigma it is (or at least was until recently, and may be becoming again). The problem was Cannon Fulbert: the tutor had betrayed the trust of the uncle. Fulbert demanded that Abelard marry Heloise. He did, but under the stricture of secrecy, which did not please Heloise. She wrote to him, in her sharp brilliant Latin, that she’d rather be his whore than his hidden wife. The marriage, it seems, was a bad idea, and things went from bad to worse. Fulbert next paid a gang of anti-Abelard hooligans (read: former students and political stooges looking for advancement in either government or, more likely, the church) to attack the lover. Abelard’s testicles were removed. Heloise gave birth to a son to whom she gave the odd and charmingly romantic-philosophical name of Astralabe.

Abelard’s castration did more than put a crimp in his relationship with Heloise. For years, it ended it. She was forced to retreat to a convent and he, eventually, into the priesthood. Long years passed until they communicated again and produced a series of famous letters.

The letters—Abelard’s autobiography, addressed to a fellow monk but which Heloise somehow obtained a copy of, her first letter to him in which she reminds him, with cutting wit, how much he owes her and begs him for consolation, and their ensuing exchange—have enchanted and illuminated students of the Middle Ages and of the modern origins of romantic love for centuries. What’s new in Burge’s book is an assessment of a cache of newly discovered letters written by the couple. These new letters were written during the affair itself and offer a wealth of juicy details and fascinating new puzzles about the couple. What, for instance, ever became of their son, Astralabe? And who put the moves on whom?

Burge, a documentary writer for the BBC and others, provides a careful and loving account of the love affair, the lives Abelard and Heloise led later in life, and Abelard’s philosophy. Burge acknowledges that sources are tricky: the letters, early and late, are all copies made by others, and therefore could be forgeries. Although he doesn’t weigh his account down with the scholarly minutia of how, in fact, academics have reached consensus on the validity of the newly discovered letters (and, indeed, about the ones we’ve always had), he does keep the Abelardian precept in mind: “By doubting we come to inquiry, by inquiry we come to truth.”

Burge’s account is indeed loving: it is hard to read the letters and not come to love the couple—or at least Heloise. She must have suffered terribly in her convent, even though she eventually became abbess, or boss nun. Her rise in power is testament to her brains, which she seemed to have always been able to apply to the problem at hand. But her heart—her heart was always elsewhere, in the hands of Abelard, who comes across as something of a schnook. A brilliant schnook, but nonetheless a schnook. Heloise’s searing testaments of her human, mundane love, which makes her “marriage” to Christ a sham, and her desire to be consoled by communication with Abelard will move even the most stolid reader, and is a swooning song of delight for the bookish romantic.