Most people in the Senate chamber noticed the sound before anything else—the sharp, sickening crack of a metal-tipped cane landing on an unprotected skull.On May 22, 1856, Preston Brooks, a young representative from South Carolina, confronted Senator Charles Sumner of Massachusetts during a visit to the upper chamber. Sumner, known for his fiery abolitionist orations, had recently given a speech leveling insults at Brooks’s kinsman Senator Andrew P. Butler, including that he consorted with “the harlot, Slavery.”Suddenly, Brooks began raining down blows on Sumner with a gutta-percha cane while an accomplice warded off lawmakers who tried to intervene. Sumner’s long legs were trapped under his bolted-down desk; the best he could do was raise his arms. Brooks beat him until the cane splintered in his hand, and then, even after the desk was wrenched free, he kept going. Finally, bystanders pulled the men apart. Sumner barely escaped death; his head and shoulders were slashed to the bone. One of America’s best legal thinkers had just been chastised like a farm animal.The attack on Sumner poured gasoline on a smoldering fire. More than 1 million copies of his speech “The Crime Against Kansas” were circulated. A little-known abolitionist named John Brown heard the news and was moved toward violent rebellion. The newly founded Republican Party, which emerged from the ashes of the establishment Whigs, campaigned that year on “Bleeding Kansas” and “Bleeding Sumner,” paving the way for Abraham Lincoln and secession. Outraged white people finally understood Sumner’s point: As long as the slaveholder oligarchy persisted, no one was free.In time, the symbols loomed larger than the men themselves: Sumner’s chair was left empty as a testament to the brutality of the “Slave Power,” and pieces of the shattered cane were hoarded like relics of the true cross. Yet as the memory of the Civil War faded, the meaning of the symbols changed; the names Sumner and Brooks became emblems of partisan rancor—a cautionary tale about the breakdown of civil discourse. As Senator Susan Collins of Maine put it in 2010: “The weapon of choice today is not the metal-topped cane, but poisonous words.”[Read: The whole story in a single photo]Over the past year, two biographers have attempted to flesh out the men behind the symbols. In Charles Sumner: Conscience of a Nation, the constitutional-law scholar Zaakir Tameez portrays his subject as the Martin Luther King Jr. of the 19th century, a man who originated key legal concepts behind civil-rights victories beyond his time. Twentieth-century historians tended to paint the senator as an ineffectual hothead, but Tameez maintains that Sumner’s in-your-face style helped shock a complacent nation into action. The case for Sumner as an underappreciated figure is stronger than it is for Brooks, a comparative mediocrity who died a year after the attack. But in The Man Behind the Cane, Paul Quigley, a Civil War historian, argues that Brooks represents an eternal archetype in American politics: “angry, alienated men” who try to expiate their failures through a “spectacular act of public violence.”Today, political violence is again on the rise. Angry, alienated men have taken shots at the president, stormed the Capitol, and attacked state legislators in their home. Each flare-up leads to a round of calls to tone down the rhetoric—even phrases such as 86 47, which anyone who works in the hospitality industry can tell you is not a violent threat—on the assumption that “poisonous words” lead to evil deeds. But in citing the infamous caning, Collins and others have lost sight of a crucial distinction. Civil-rights movements that challenge an oppressive status quo usually provoke a disproportionate response; in fact, the strategy of nonviolent resistance depends on it. The lives of Sumner and Brooks demonstrate that harsh words do incite violence—but also that they can topple the structures that perpetuate it.In retrospect, Sumner seemed predestined to become a famous abolitionist lawyer. Born in 1811, he grew up poor on the North Slope of Beacon Hill, Boston’s largest Black enclave at the time, and developed a lifelong empathy for his neighbors. His father, Charles Pinckney Sumner, alienated many Bostonians with his support for interracial marriage and the integration of schools. Still, the elder Sumner maintained important connections, and young Charles, a voracious reader, attended Harvard’s new law school. He was also hypersensitive to criticism; even as a senator, when he felt particularly misunderstood, he would go home and cry.But in public, he was formidable, “a six-foot-four Bostonian lawyer with a wild mane of chestnut hair, thick sideburns, broad shoulders, and a sonorous voice that could roar like a lion,” Tameez writes. Sumner lost many friends in high society in 1845, after he delivered a blistering address against the slaveholder expansionism fueling the Mexican-American War. Yet he acquired new patrons, among them former President John Quincy Adams, who was a mortal enemy of slavery.Elected to the Senate in 1851 as a member of the Free-Soil Party, Sumner became America’s foremost abolitionist, better known at the time, according to Tameez, than William Lloyd Garrison and Frederick Douglass. Public oratory was the dominant political medium of the day, and Sumner mastered it. His hours-long speeches, stuffed with classical allusions and thundering with invective, were distributed as pamphlets by the millions. The plantation class saw his rhetoric as a physical threat because it could inspire slaves to rise up and kill their masters, and northern moderates considered it recklessly divisive. The latter hoped to let slavery die out naturally—a short-sighted view, Sumner thought, because it only delayed inevitable confrontation.[Read: The annotated Frederick Douglass]Having begun his tenure as a fringe figure, one of three abolitionists in the Senate, Sumner became ever more the standard-bearer for northern resistance. Unaccustomed to being challenged in person, the southern plantation owners who ran the Senate were at first stunned, and then outraged. Sumner sat behind Andrew P. Butler, a venerable sot from South Carolina who spat his chewing tobacco directly onto the floor. Butler “made a laughingstock of Sumner’s bachelorhood,” Tameez writes, “suggesting he fantasized about Black women.” (The author speculates that Sumner may have been gay.)On May 19 and 20, 1856, Sumner repaid the favor. Delivering “The Crime Against Kansas,” his speech condemning the scheming politicians sowing violence in the disputed territory, Sumner held forth from memory for five hours. He reserved special derision for Butler, a “Don Quixote” of the South who had made a knightly vow to his “mistress,” slavery. Sumner also mocked the “loose expectoration” of Butler’s speech—a low blow, because the senator had been physically impaired by a stroke. These disparagements cut to the core of southern manhood. That was intentional; Sumner had studied the plantation class’s honor code. The man who would punish him for the speech was born into it.Edgefield, South Carolina, was a slaving town with a violent reputation, a place where men roamed with swords and pistols, ever ready to avenge an insult. “The spilling of human blood or taking human life is regarded with very little more repugnance or abhorence [sic] than killing a wild beast,” Whitfield Brooks, Preston Brooks’s father, once lamented. Nevertheless, the elder Brooks, a hard-bitten local aristocrat and slaveholder, believed strenuously in the code of the South. Men were masters over their women, their chattel, and their emotions. Preston, the eldest son, was expected to embody that ideal.Time and again, he failed. The young Brooks’s disciplinary problems began with fights in primary school and culminated in his expulsion from college for threatening a policeman with a firearm. At 21, after a prolonged dispute, he fought a duel with a man who had insulted a friend. On an unnamed island in the Savannah River, the two men turned and fired, and each was hit in multiple places. For the rest of his life, Brooks walked with a cane.Quigley mines the spectacle and proceduralism of southern culture with an eye for Twainian comedy—a long chapter is devoted to Brooks’s desperate bids for glory during the Mexican-American War—but he is also alert to the serious lessons that Brooks learned from the beatings he took. For gentlemen of that era, uncivil words were violence. A man stripped of honor was no man at all.[Read: The lesser part of valor]Sumner’s uncivil words against Butler provided Brooks with the opportunity to make up for a lifetime of misadventures. By caning Sumner, he succeeded almost too well. The repercussions for Brooks were minimal; a criminal court fined him $300, and a vote to expel him from the House failed. He resigned in protest anyway and was reelected resoundingly by his constituents. Yet at the height of his triumph, Brooks was uneasy. “I feel that my individuality has, in a great measure, been destroyed,” he told a group of statesmen who had gathered to celebrate him at a banquet. To his chagrin, he had become “the type and representative of the entire South.”In January 1857, Brooks died suddenly of croup. He would remain a type and representative of the culture that his public brutality, by leading to the Civil War, had helped destroy. Sumner, despite his lasting injuries, lived longer and accomplished more. Tameez credits him as a prime intellectual force behind the Emancipation Proclamation and the Thirteenth and Fourteenth Amendments. He wrote the Civil Rights Act of 1875, which was passed the year after his death and became the model for the Civil Rights Act of 1964. A school-integration case he argued in the 1840s inspired Brown v. Board of Education. The list goes on.The caning, perhaps the most significant event of Brooks’s undistinguished life, also overshadowed Sumner’s accomplishments. This may be because it made him a type as well; he was the brave northerner, silver-tongued and quick-witted, laid low by southern thuggery. Yet even as a victim, he had shown Americans that when it came to slavery, compromise was no longer an option, and violence might be inevitable.Generations of activists built on Sumner’s legacy, carrying forward both his legal ideas—he likely coined the phrase equality before the law—and the strategy of nonviolent confrontation. When the Selma marchers faced down snarling dogs and baton-wielding police in 1965, the contrast between their passive resistance and the Jim Crow officials’ savagery echoed the caning of a century before.Six decades on from Selma, different parallels come to mind. ICE’s siege of Minneapolis bears traces of 19th-century conflicts over the Fugitive Slave Act, which brought federal agents face-to-face with abolitionist protesters in northern cities. Donald Trump’s insistence that calling him an authoritarian puts him in physical danger recalls those southerners who treated sharp challenges as fighting words. Direct historical comparisons are dicey, and violence is never the exclusive province of one political movement (think of John Brown). But in every era of conflict, some well-meaning moderates have enabled bad-faith censors by conflating confrontational speech with the violence that sometimes answers it. Many successful activists, however, have achieved their goals by heightening the contrast between words and weapons. In this way, each generation receives its painful reminder that those two things are not the same.