Of the private thoughts of medieval people we know almost nothing. They kept no journals. We have lost their conversations. The relatively few letters that survive take little or no interest in self-analysis, for the self had none of the importance it was given later. Hence the preciousness of the letters exchanged in the early 12th century by Héloïse and Abelard. They spoke of love with a frankness that had not been heard since the time of Ovid and Catullus. “Body full of moisture, that indescribable scent of yours,” wrote Abelard to Héloïse. “Everything we did, and also the times and places are stamped on my heart along with your image, so that I live through it again and again with you,” she wrote to him. Little wonder that they have become the informal patron saints of lovers, or that their monument in the cemetery of Père Lachaise in Paris is always strewn with flowers.

He was the most brilliant logician of his day, the star of the nascent Paris schools, a performer, a song-maker and a philosopher. She, perhaps 15 years his junior, was his star pupil. He was allowed by her Uncle Fulbert to teach her privately, which led to the inevitable: “my hands [straying] more often over the curves of her body than to the pages”. Within two years, in 1117, the affair was known. When Héloïse became pregnant, Abelard smuggled her to Brittany; they agreed to a secret marriage, which proved unworkable. Finally, Abelard dispatched her to a convent, which she decided on only because she loved him. He was violently castrated, probably by Fulbert’s servants.

For the rest of his life, Abelard tried to make amends by teaching and running monasteries. His lecturing was as sharp and uncompromising as ever, his management of monks hopeless; he made enemies everywhere. Héloïse, meanwhile, repented none of her passion for him. She remembered their lovemaking even in the middle of mass; her life as a nun was devoted both to Christ and to him. In 1129, she became abbess of the Paraclete, an institution originally founded by Abelard in the wilderness. They resumed a careful, businesslike contact, he writing hymns for her community like the songster she had first loved. In the end, he was buried in her church, as he had asked.

Their story has been told many times, most famously by Helen Waddell in the 1930s. It is refreshed here by the apparent discovery of new letters between the lovers: a finding made in 1980 and still working its way into academic acceptance. The letters seem to have been incorporated into a 15th-century manual of letter-writing. They survived, James Burge surmises, because Héloïse preserved on parchment the original fleeting messages that were written on wax tablets. It is hard to believe she would have done this at the height of a secret affair. In fact, the new letters (a jumble of lovers’greetings and tiffs in standard medieval style) add little to the story. It is good enough without them.

It is also well worth retelling, especially for an age in which the spiritual imperatives behind this passion have become incomprehensible. Burge explains what was going on in his subjects’ heads, and why it mattered so much to them to try to reconcile their physical love with obedience to God. He is clear on the background, giving just enough without overburdening the reader, and on the tortuous philosophical jousting that Abelard so enjoyed. The walk-on parts of Abbot Suger and Bernard de Clairvaux are full of life, and the two lovers are as vivid as one could wish, though it is hard to see how Héloïse could have fallen so hard for such an insufferable egoist no matter how dazzling he was in the classroom or in bed.

The most striking part of the book is, oddly, its modernity. Abelard and Héloïse are, in some ways, startlingly contemporary: Abelard for his belief that reason could explain almost anything, including the Trinity, Héloïse for her defiant intelligence and refusal to compromise her love. Burge sometimes plays this up too much; I don’t want to meet the words “management skills”, “chief executives” or “bums on seats” in a book on the 12th century, or read that Héloïse “would have been aware of the continuing development of medieval society”, for I’m sure she wasn’t. Nonetheless, at many points (and perhaps especially when he refers to the letters scrawled on wax tablets as “teenage text messages”), Burge achieves something truly difficult: he reminds us that, for Abelard and Héloïse, their world was as new, risky and unpredictable as ours is, and every day as fresh with possibilities. Teenage texters, and many others, can now enjoy this story all over again.

Ann Wroe’s Perkin: A Story of Deception is published by Cape. Héloïse & Abelard is available at the Books First price of £13.59 plus £1.95 p&p on 0870 165 8585

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