Among my fellow punctuation nerds, I have a reputation as someone who has no use for semicolons. I don’t hate semicolons; I hate writing about semicolons. Fortunately, now I don’t have to, because Cecelia Watson, a self-identified “punctuation theorist” who teaches at Bard College, has written a whole book about them: “Semicolon: The Past, Present, and Future of a Misunderstood Mark.”

At first, I thought Watson was doing with the semicolon what Simon Griffin did with the apostrophe in “Fucking Apostrophes” (2016). Both are slim volumes about an element of language that gives people endless grief. But whereas Griffin, an adman, provides straightforward rules, albeit with a bushel of exceptions (and a running joke: every use of the word “apostrophe” is preceded by a profanity), Watson, a historian and philosopher of science and a teacher of writing and the humanities—in other words, a Renaissance woman—gives us a deceptively playful-looking book that turns out to be a scholarly treatise on a sophisticated device that has contributed eloquence and mystery to Western civilization.

The semicolon itself was a Renaissance invention. It first appeared in 1494, in a book published in Venice by Aldus Manutius. “De Aetna,” Watson explains, was “an essay, written in dialogue form,” about climbing Mt. Etna. Its author, Pietro Bembo, is best known today not for his book but for the typeface, designed by Francesco Griffo, in which the first semicolon was displayed: Bembo. The mark was a hybrid between a comma and a colon, and its purpose was to prolong a pause or create a more distinct separation between parts of a sentence. In her delightful history, Watson brings the Bembo semicolon alive, describing “its comma-half tensely coiled, tail thorn-sharp beneath the perfect orb thrown high above it.” Designers, she explains, have since given the mark a “relaxed and fuzzy” look (Poliphilus), rendered it “aggressive” (Garamond), and otherwise adapted it for the modern age: “Palatino’s is a thin flapper in a big hat slouched against the wall at a party.”

The problem with the semicolon is not how it looks but what it does and how that has changed over time. In the old days, punctuation simply indicated a pause. Comma, colon: semicolon; period. Eventually, grammarians and copy editors came along and made themselves indispensable by punctuating (“pointing”) a writer’s prose “to delineate clauses properly, such that punctuation served syntax.” That is, commas, semicolons, and colons were plugged into a sentence in order to highlight, subordinate, or otherwise conduct its elements, connecting them syntactically. One of the rules is that, unless you are composing a list, a semicolon is supposed to be followed by a complete clause, capable of standing on its own. The semicolon can take the place of a conjunction, like “and” or “but,” but it should not be used in addition to it. This is what got circled in red in my attempts at scholarly criticism in graduate school. Sentence length has something to do with it—a long, complex sentence may benefit from a clarifying semicolon—but if a sentence scans without a semicolon it’s best to leave it alone.

Watson has been keeping an eye out for effective semicolons for years. She calculates that there are four-thousand-odd semicolons in “Moby-Dick,” or “one for every 52 words.” Clumsy as nineteenth-century punctuation may seem to a modern reader, Melville’s semicolons, she writes, act like “sturdy little nails,” holding his wide-ranging narrative together. She is delighted with the “springy little semicolons” of Irvine Welsh in “Trainspotting” (“The sweat wis lashing oafay Sick Boy; he wis trembling”) and she has a special fondness for the rare semicolon in Raymond Chandler, whose hardboiled private detective, Philip Marlowe, is not given to periodic sentences. In “The Big Sleep,” for instance, Marlowe describes his room: “In it was everything that was mine, that had any association for me, any past, anything that took the place of a family. Not much; a few books, pictures, radio, chessmen, old letters, stuff like that.” In Watson’s perception, that choice of a semicolon after “Not much” creates a reflective silence. “The semicolon reads as Marlowe having to stop to think.”

A sentence from Wittgenstein contains a “fantastically vague semicolon”: “Der Philosoph behandelt eine Frage; wie eine Krankheit.” (“The philosopher treats a question; like an illness.”) This has been translated by G. E. M. Anscombe thus: “The philosopher’s treatment of a question is like the treatment of an illness.” But, in removing what Erich Heller, an expert in German philosophy, calls a “profound” semicolon, one that “marks a frontier between a thought and a triviality,” the translator has reduced a deep thought to a bland one. Watson writes, sounding like the “punctuation therapist” she sometimes plays, “Ambiguity can be useful and productive, and it can make some room for new ideas.”

Watson is especially thought-provoking on the topic of semicolons and the law, where ambiguity can lead to trouble. In Massachusetts, a semicolon that should have been a comma would have prevented hotels from selling liquor after 11 P.M.; it had the effect of making people buy a lot of drinks before last call. Worse, in a New Jersey murder trial in 1927, sloppy punctuation caused one of the defendants, Salvatore Rannelli, to be sentenced to life imprisonment while the other, Salvatore Merra, was sentenced to death—for the same crime. Legal cases are often built on precedent, and a judgment based on flawed punctuation sets a bad precedent, which can perpetuate injustice.

The semicolon’s two main detractors, the antiheroes of Watson’s book, are Donald Barthelme and Kurt Vonnegut, with Chandler complaining about a proofreader at The Atlantic (one Margaret Mutch) and Mark Twain weighing in on the ignorance of proofreaders in general. Barthelme found the semicolon “ugly as a tick on a dog’s belly.” Vonnegut wrote that semicolons are “transvestite hermaphrodites representing absolutely nothing,” a statement that makes me feel only more sympathy for the semicolon. What’s wrong with hermaphrodites?

Henry James, who would have been my choice for Master of the Semicolon, turns out to have been famous during his lifetime for his use of dashes. Watson writes that the dash “cutting a path” through any page of James is “an arm outstretched as a barrier to keep one thought from tumbling into the next.” She has unearthed an interview, from 1915, that James gave to a reporter for the Times, in which the Master (who did not do interviews, and on this occasion insisted that the reporter note “his punctuation as well as his words”) remarked that dashes “strike both the familiar and the empathic note . . . with a felicity beyond either the comma or the semicolon; although indeed a fine sense of the semicolon, like any sort of sense at all for the pluperfect tense and the subjunctive mood . . . seems anything but common.” Watson observes, “We live in the Era of the Dash”—which is probably just as well.

Both the dash and the semicolon are put to brilliant use in a page-and-a-half-long sentence from “Letter from Birmingham Jail,” which Watson quotes in full. In it, Martin Luther King, Jr., details the miseries of a black man, a victim of injustice, who is asked to wait patiently for change. King piles up clause after clause, each describing a more harrowing, frustrating event than the last, and each lofted by the semicolon that concludes the one before: “when you are humiliated day in and day out by nagging signs reading ‘white’ and ‘colored’; . . . when you are forever fighting a degenerating sense of ‘nobodiness.’ ” The litany rises to a crescendo delivered with a dash: “—then you will understand why we find it difficult to wait.” Watson concludes that “this is mimesis at its finest”; the semicolons hold the prose “in suspension,” and the reader in suspense, waiting, along with King, for justice. Of course, King’s letter is about much more than punctuation, but here is an instance in which the semicolon did its small part for civil rights.

On Sunday night I texted my twin brother, Chris, who lives in San Francisco, and asked him to excavate his memory about the bullying we’d experienced for being Asian while growing up. Our family moved around several times during our childhood: we spent elementary school in a Pittsburgh suburb; middle school was in upstate New York; high school was in Michigan. The schools we attended were almost exclusively white, and being Asian-American inevitably shaped our ability to navigate the social hierarchies that circumscribe the lives of all children. Some of the epithets we dredged up, in our texts: La Choy. Me Chinese, me play joke, me go pee-pee in your Coke. Ching chong. I remembered middle school as being the worst, but Chris thought that the teasing in elementary school was more pervasive. “We were more established in middle school,” he said. He pointed out that we’d managed to attach ourselves to a group of popular kids, and that had insulated us to some degree. But I still recalled ugly moments, including one when a friend—indisputably one of the cool kids—had to put a stop to the harassment. What Chris remembered—and it was what I remembered, as well—was the feeling of perennially being “on the outside looking in.” It’s a sense that persists for both of us today, at a constant low thrum.

On Sunday morning, President Trump suggested on Twitter that four congresswomen of color, Alexandria Ocasio-Cortez, Ilhan Omar, Rashida Tlaib, and Ayanna Pressley, should “go back” to the countries “from which they came.” The racist diatribe came in a string of tweets, separated by ellipses.

Many have already pointed out the fallacies in Trump’s tweets. Three of the women were born in this country; only Omar, who emigrated from Somalia, was not. Tlaib’s parents are Palestinian immigrants; Ocasio-Cortez’s parents are of Puerto-Rican descent. Pressley is black. They are all, of course, Americans. But it is worth pausing to recognize the racist shibboleths in Trump’s tweets, ones that have been used to justify other shameful moments in our history, from the Japanese internment, during the Second World War, to the Trump Administration’s Muslim ban.

As an editor, my normal instinct regarding Trump’s tweets has been not to engage, to avoid becoming an unwitting abettor of his attention economy. But Sunday’s tweets felt different to me. They were too dangerous to go unchallenged, the path from words to action too well trodden. There’s the assumed association with the countries of the congresswomen’s ancestry, a trope that has been used to question the loyalties of immigrants throughout American history. There’s the us-versus-them delineation in the language around “our government.” There’s the reproach to get out. On Sunday, I searched Nexis, a newspaper database, for variants of “go back to your country” and “murder” or “attack.” Some of what I found:

On February 22, 2017, Srinivas Kuchibhotla was having drinks after work with his best friend, Alok Madasani, at Austin Bar & Grill, in Olathe, Kansas. Kuchibhotla and Madasani both worked as engineers at Garmin, the G.P.S.-technology firm. Austin was a regular spot for them after work. A white man approached and demanded to know their immigration status. His name was Adam W. Purinton. He was fifty-one, a Navy veteran, and a regular at Austin. He continued to heckle the two friends and hurl ethnic slurs before other patrons intervened and escorted him from the premises. A short while later, he returned with a gun and opened fire, killing Kuchibhotla and wounding Madasani, as well as a bystander who chased after Purinton. Witnesses said that before Purinton started shooting, he yelled, at the men, “Get out of my country.”

In July, 2018, Rodolfo Rodriguez, a ninety-one-year-old resident of Willowbrook, a neighborhood south of downtown Los Angeles, was going for a walk when he passed a woman and a child on the sidewalk and suddenly found himself being beaten with a concrete brick. A witness said that she heard the woman, who was later identified as Laquisha Jones, shout, at Rodriguez, “Go back to your country. Go back to Mexico.”

In February, in Indianapolis, Mustafa Ayoubi, a thirty-three-year-old immigrant from Afghanistan, was shot to death by a man named Dustin Passarelli. Witnesses alleged that Passarelli yelled slurs about Islam and told Ayoubi, “Go back to your . . . country.” (Passarelli disputed the account.)

It was on the eve of Trump’s election, in October, 2016, when I experienced my own “go back to your country” moment. (I wrote about the incident in a column for the Times.) My family and I had just got out of church, and we were looking for a place to go for lunch. We were with some friends—all of us Asian-Americans—when a well-dressed white woman grew agitated at our group, because we were partially blocking the sidewalk. After she sidled past, she turned to yell at us, “Go back to China!” I was momentarily shocked, but then I abandoned my toddler in her stroller to confront the woman. As I was walking away, she screamed, “Go back to your fucking country.” To this day, I still think about what I hollered back: “I was born in this country!” As if that’s all I needed to prove.

The weariness that rose up inside me in the aftermath was, in large measure, for my two children. Even three generations removed from the immigrant experience, I wondered whether they’d ever feel a sense of belonging in this country. I happen to be currently reading Ocean Vuong’s extraordinary semi-autobiographical new novel, “On Earth We’re Briefly Gorgeous.” The story of the book’s narrator, Little Dog, closely aligns with that of Vuong, who was born in Vietnam, came to this country as an adolescent, and couldn’t speak English when he started school in Hartford. In Vuong’s novel, Little Dog experiences a harrowing incident on the school bus, when he finds his face suddenly shoved against the window by a jowly boy, who admonishes him to “speak English.” Slaps from the boy and others rain down on him before they get distracted and lose interest. “He was only nine but had mastered the dialect of damaged American fathers,” Vuong writes, of the aggressor. As Trump stokes the racial fears of the millions of white Americans who are uneasy about the demographic changes unfolding in this country, it is that dialect he is championing. And it is the lot of so many immigrants, children of immigrants, and people of color in this country to wonder whether we can ever truly belong here, and who gets to decide.

One striking aspect of the oral arguments, last week, in Texas v. United States, a case that threatens the Affordable Care Act, was the suggestion, from two of the three judges on a Fifth Circuit appeals panel, that what politicians say to or promise the public needn’t be taken seriously—indeed, that it hardly matters if they lie. The case, which I wrote about in this week’s magazine, was brought by states led by Republicans, and in effect argues that, when Congress passed President Trump’s 2017 tax bill, it was, unbeknownst to the public, actually invalidating the entire A.C.A. One roadblock to this argument is that this is not what Congress said it was doing. Instead, the law simply set the penalty for not securing health insurance—the “individual mandate”—to zero, and nothing more. But why should anyone believe them?

“How do we know that some members didn’t say, ‘Aha! This is the silver bullet that’s going to undo the A.C.A.’ or ‘Obamacare,’ if you prefer?” Judge Jennifer Elrod asked Samuel Siegel, an attorney defending the law on behalf of a group of twenty-one states, most of them blue. “ ‘So we’re going to vote for this just because we know it’s going to bring it to a halt, because we understand the tax issue’?” (The “tax issue” is the theory that, because Chief Justice John Roberts once argued that defining the financial penalty as a tax made that penalty constitutional, its absence was fatal to the whole law—an argument that lawyers might want to keep secret not out of tactical slyness but out of embarrassment, because it doesn’t make much sense.)

“That would be imputing to Congress the intent to create an unconstitutional law,” Siegel said, though it’s actually more convoluted than that. Indeed, the hypothesis is that members of Congress passed such a law just to be busted—to sabotage a law that they had failed to change legislatively. (At another point, Elrod asked whether Texas, one of the lead plaintiffs, might have been waiting to say, “ ‘Hah—caughtchya! You just did something unconstitutional!’ ”) When the penalty was repealed, Siegel noted, several legislators “specifically came forward and said, ‘We are not repealing the preëxisting conditions, we’re not repealing the subsidies’ ”—elements of the A.C.A. that are widely popular. If they did have a “silver bullet” plan, “that would mean they were misleading the American public and their constituents.” Senator Orrin Hatch, then the Republican chairman of the Finance Committee, was among those offering such reassurances in 2017.

“I’m not a fan of using quotes from elected officials, who say a lot of things for a lot of reasons,” Judge Kurt Engelhardt said. Engelhardt, whom Trump named to the court, came across as a silver-bullet kind of guy. An issue in the case is “severability”—how much of a large, multi-part law courts should invalidate if one element of it is found unconstitutional. The basic standard is that courts should be cautious and keep what they can. Engelhardt asked why it wouldn’t be easier to just throw out the whole thing and let Congress start over. “I mean, can’t they put together a sort of cafeteria-style package with all of these individual features that are so attractive . . .  They could vote on this tomorrow!” he said to Douglas Letter, a lawyer for the House of Representatives, who was also defending the bill. “Couldn’t they put them together and vote on them like that?” Engelhardt asked, snapping his fingers.

“And obviously the President would sign that, right? No, obviously not,” Letter replied, provoking laughter.

In the health-care case, the public reassurances from legislators simply reinforce the most obvious reading of the law, namely that Congress had decided that the mandate could go and the rest of the law could, functionally, survive without it. But an interesting phenomenon, in the jurisprudence of the Trump years, involves attempts by the Administration’s lawyers to get the courts to ignore a disjunction between what the President says in public and the legal justifications that his Administration offers for his actions. In the litigation over the various iterations of Trump’s travel ban, for example, lawyers for the Administration argued that judges should ignore what Trump said on the campaign trail about instituting “a total and complete shutdown of Muslims entering the United States until our country’s representatives can figure out what the hell is going on,” as well as his tweets disparaging Muslims. Instead, the judges should believe the lawyers’ claims that the ban was not targeted at any religious group and was not at all discriminatory: the ban was just a reflection of concerns about national security. It took a few tries, major revisions, and the inclusion of North Korea on a short list of proscribed countries for the Administration to come up with a limited ban that the Supreme Court, by a 5–4 vote, would accept.

Similarly, the Administration, in its attempts to add a citizenship question to the census, first claimed that the aim was to protect the voting rights of minorities—a rationale laughably at odds with the President’s warnings of an immigrant invasion. The question of how courts should interpret the meaning of legislative and executive actions has always been complicated; Trump’s tendency both to dissemble and to incite, both to deny his motives and to bray about them, all at high volume, can make it trickier still. In the census case, though, the President lost: the Supreme Court found that his Administration had not offered a good-faith explanation for adding the question. The ruling meant, practically, that the question would be omitted; the task of having to justify its actions in an honest manner was apparently too daunting for the Administration to accomplish in the time left before the forms had to be printed. Chief Justice Roberts, writing for the majority, wrote (citing an earlier decision), “We are ‘not required to exhibit a naiveté from which ordinary citizens are free.’ ” The Court wanted the Trump Administration to tell the truth about what it was doing. Or, at least, the Court didn’t want the President to force it to pretend to believe his more obvious lies.