A 1910 painting called Sisters by Kazimir MalevichFine Art Images / Heritage Images / Getty Images

Did you register, dear viewer, that Downton Abbey had two characters named Thomas B: the malignant footman turned loyal butler Thomas Barrow, and the socialist chauffeur turned son-in-law Tom Branson? And if it did, did it bother you?

Chances are the answer is no—unless you happen to be Benjamin Dreyer.

Dreyer is an expert grammarian and influential arbiter of good writing, whether in the novels he oversees as the copy chief at Random House, or on Twitter, where he points out the proper use of the em dash, commonly misspelled names (Olivia Colman), and that while it’s kosher to spell omelette as omelet, dialog is beyond the pale, “Because ick.” This blend of pedantry and whimsy makes his new book, Dreyer’s English: An Utterly Correct Guide to Clarity and Style, an instructive and entertaining manual—one that lays down the law of the jungle while being imaginative enough to allow personal idiosyncrasy to prosper.

But there’s at least one area where Dreyer displays a surprisingly rigid point of view. In advice that has the whiff of schoolroom dogma, he exhorts novelists to refrain from giving characters similar-sounding names. Citing a manuscript he had to edit, where “fully half the characters had names beginning with the letter M,” Dreyer intones, “This is not a good thing.” In the footnotes, he offers the example of Downton Abbey: “It was a point of ongoing perturbation for me that two characters on the Downton Abbey series were both—pointlessly, so far as I could discern—named Thomas and that both their surnames began with a B.

No doubt the motive behind his rule is to avoid confusing the reader. But clarity is only one aspect to choosing a character’s name, and it would’ve been helpful if Dreyer had explored the significance of deploying same or similar-sounding names as a literary device, though he gestures to it by qualifying his criticism of the two Thomases with, “pointlessly, so far as I could discern.” The inference being that if there were a larger point, he might not object.

In comedy, for instance, the same-name device is commonplace, as in the delightful case of Thompson and Thomson, the bungling Scotland Yard detectives in the Adventures of Tintin comic series, alike in everything but the curl of their mustache. The contorted ways in which they introduce themselves, including, “This is Thompson, yes, with a P as in Philadelphia” and “This is Thomson, no without a P, as in Venezuela,” never fail to spark joy.

But it’s also a useful ploy to add dramatic tension. In Olive Kitteridge, the Pulitzer Prize–winning novel by Elizabeth Strout (who, incidentally, is the only author whom Dreyer continues to copy edit), two couples gather around the Kitteridges’ dining table: the middle-aged Henry and Olive Kitteridge, and the newly married Henry and Denise Thibodeau. Olive’s bottled resentment—at being forced to play host, at her drudgery-filled life, at her husband’s infatuation with Denise—explodes when her Henry spills the ketchup while passing it to the other Henry. She snaps at her husband, but the damage her outburst inflicts is collateral.

“Leave it,” Olive commanded, standing up. “Just leave it alone, Henry. For God’s sake.” And Henry Thibodeau, perhaps at the sound of his own name being spoken sharply, sat back, looking stricken.

It’s as if the blood spatter of Olive’s bullet, aimed at her Henry, has landed on the other Henry’s face. Soon, this young Henry will die in a hunting accident, leaving Henry Kitteridge to comfort Denise, who will whimper, “Oh Henry, Henry,” so that he is painfully uncertain about “which Henry she meant.” The reader, too, is left wondering whether Denise is mourning the dead Henry, playing the older Henry, or flailing between the two. All that misdirection achieved simply by naming both men Henry.

But Dreyer’s complaint was that because the two Thomas B’s didn’t do anything to enrich Downton Abbey, why have similar names? To which, one can answer, Why not? The overlapping of names is an all-too-common occurrence in life. True, it can cause confusion (especially for the accounts department), but if fiction’s grand purpose is the mimesis of la condition humaine, shouldn’t writers be nudged to accommodate this inconvenient reality, rather than dodge it for fear of taxing the reader? If accounts can handle it, can’t we?

Yes, we can, declares the twice-Bookered Hilary Mantel, whose experience in managing dramatis personae bedeviled by the same name is hard to surpass. In her Tudor trilogy (Wolf Hall, Bring Up the Bodies, and the forthcoming The Mirror and the Light), all the leading male characters apart from Henry VIII are named Thomas (it was the second-most-popular name in Tudor England). There is Thomas Cromwell, the ruthless hero. Thomas Wolsey, the Catholic cardinal. Thomas More, the Catholic zealot. Thomas Cranmer, the archbishop of Canterbury. And Thomas Boleyn, the depraved father of Anne Boleyn, and the only one of these Thomases to survive the abattoir of the Tudor court. The naming nightmare, however, doesn’t end here. Of Henry’s six wives, three are some variation of Catherine and two are Anne, while his mistress, his daughter, and the Queen of Scots are all Mary.

Mantel was writing historical fiction and had no say in the christening, but she embraced her cards. “What do I do?” she said in 2014 at the Cheltenham Literature Festival, on the difficulties of adapting her books for television. “Every second man in Henry VIII’s England is called Thomas. At any one time, there are five Thomases on the page, all shouting at each other. The only thing to do is let the reader in on it. Admit the difficulty … Because as soon as you decide this is too complicated for the viewer, or history is an inconvenient shape and can’t we tidy it up a bit, then you fall into a cascade of errors which ends in nonsense.”

But what if a novelist were to write a fictional story of a Tudor tyrant? Only a sadomasochist would name five men Thomas. Unless, of course, your novel is set in the looking-glass world of Macondo. In Gabriel García Márquez’s One Hundred Years of Solitude, which Netflix is set to adapt, the 17 sons whom Colonel Aureliano Buendía fathers during his war travels by 17 women are all baptized Aureliano. And all but one are murdered by the colonel’s enemies. The hyperbolic naming could be dismissed as another magical-realism stunt—except that it is curiously convincing. First, because it is breathtakingly realistic for those mothers to give their sons the first name of their illustrious father because they can’t carry his surname. And second, because García Márquez treats the serial massacre not as a video-game splatterfest but as the appalling family tragedy that it is. As the telegrams announcing the deaths of the Aurelianos arrive in Macondo, the boys’ aunt Amaranta brings out the family ledger, and like a meticulous accountant, draws lines through her nephews’ names, until only the eldest remains. Nothing evokes the looming obliteration of the Buendías more chillingly than the crossing out of Aureliano 16 times over.

One writer who uses the same-name trope masterfully, both as a reflection of life and for dramatic tension, is le grand écrivain of realism: Leo Tolstoy. I was finally spurred to read Anna Karenina after coming across this observation in The Possessed, Elif Batuman’s travelogue into Russian literature.

Anna’s lover and her husband had the same first name (Alexei). Anna’s maid and daughter were both called Anna, and Anna’s son and Levin’s half brother were both Sergei. The repetition of names struck me as remarkable, surprising, and true to life.

To have a scattering of Annas and Sergeis in a Russian novel is an authentic touch. But to give husband and lover the same first name is a florid ruse that enables Tolstoy to indulge his moral snobbery at adultery and, conversely, to expose the illusion of choice within which Anna is trapped. She refers to this cruel coincidence only once, in that anguished scene that every reader has been secretly hoping for: a confrontation between her and the two Alexeis. It unfolds after Anna has given birth to her lover’s daughter and is almost at death’s door. Crying out for forgiveness, she calls her husband Alexei, and not the formal Alexei Alexandrovich, for the first and last time.

For Alexei—I am speaking of Alexei Alexandrovich (what a strange and awful thing that both are Alexei, isn’t it?)—Alexei would not refuse me.

Moved by her remorse, Anna’s husband (whose family name is Karenin) forgives her. In this scene, Anna is at the peak of her powers and has complete control over the two Alexeis, with one sobbing against her skin, and the other into his hands. Rounding off this tableau are the two other Annas, the loyal maid (who’s known as Annushka throughout) and the newborn, who will be christened Anna (her precarious social status being no different from the 17 Aurelianos). Anna Karenina will never have the same power again, and the two Alexeis will parallel her narrow life like the train tracks onto which she eventually flings herself. Karenin, who is strangely enchanted by his wife’s daughter, will adopt her from the bereft Alexei Kirillovich Vronsky, thus officially making her Anna Karenina. The little girl will repeat, in reverse, the journey her mother made from one Alexei to the other.

Would the novel have been as heartbreaking if Karenin and Vronsky had different first names? It would. But the fact that they do injects the romance with a moral queasiness, something that the Tolstoy devotee and Olive Kitteridge author Elizabeth Strout was probably aware of when she named her two male characters Henry. Similarly, the fate of the numerous Thomases concentrates the carnage of the Tudor court, and the massacre of 16 Aurelianos infuses a family saga with mythic weight.

As for Downton, the two Thomas B’s are probably mere coincidence. But coincidence can instruct without meaning to. In this case, the trajectory of the two men inadvertently exposes the travesty of the class system, which forms the scaffolding and substance of this family drama. Both commoners start out downstairs, until one marries well and is absorbed upstairs. One Thomas B will be treated as the pantry man, the other Tom B as posh. The porousness of the rigid class system is almost parodic, but has allowed it to survive and prosper. Very much like the English language, as Dreyer’s book so amply testifies.

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