For the last couple of centuries, the word ''radical'' referred to people who try to pull things up from the root. After the Civil War, Radical Republicans, as they were called, pushed Reconstruction policies through Congress on behalf of freed slaves, trying to tear down the plantation-based power structure of the antebellum South. Eugene Debs, the most prominent socialist of the early 20th century (and a hero to Bernie Sanders), ran for president five times on what was seen as a radical platform of condemning capitalist oppression.
Change that is ''radical'' is ''essential and fundamental'' or ''far-reaching,'' according to the Oxford English Dictionary. About 50 years ago, surfers pressed ''radical'' into service to describe extreme waves. It became generic slang for anything remarkable or worthy of attention, sometimes shortened to ''rad'' and often paired with ''totally.'' In its other meanings, ''radical'' has retained its potency as well as a hint of the uncontrollable. (In chemistry, ''free radicals'' are especially jittery atoms containing unpaired electrons.) ''Radical chic'' was the mocking phrase Tom Wolfe coined in New York magazine in 1970 for the celebrity feting of militants. Reeling off a list of attendees at a party in Leonard Bernstein's Manhattan penthouse, he built to the crescendo ''. . . and now, in the season of Radical Chic, the Black Panthers.''
Right now we're most likely to see ''radical'' paired with ''Islam'' in news stories and conversations about the motivations of the San Bernardino shooters, Tashfeen Malik and Syed Rizwan Farook. Yet many Muslims reject the term ''radical Islam.'' They say that ISIS's reading of the Quran and other texts is so selective as to be unrecognizable as Muslim at all. Dar al-Ifta, an authority on Islamic law in Egypt, asked the media and others to stop referring to ISIS as ''the Islamic State'' and instead use the name QSIS, for Qaeda Separatists in Iraq and Syria.
President Obama and Hillary Clinton live in the world of politics, where rhetoric is often more heated, but they avoid using ''radical Islam'' or ''jihad'' to describe the terror driven by ISIS. After the group took credit for the attacks in Paris that killed 130 people last month, Obama said that Muslims around the world were our allies and encouraged them ''to ask very serious questions about how did these extremist ideologies take root, even if it's only affecting a very small fraction of the population.'' He and Clinton have warned that defining ISIS in terms of Islam -- even with ''radical'' attached -- risks alienating Muslims and handing ISIS a recruitment tool. ''It helps to create this clash of civilizations,'' Clinton said the weekend after the San Bernardino shootings.
But Republican candidates for president charge Obama and Clinton with making a dangerous denial in linguistic form. ''Look, we are having a tremendous problem with radical Islamic terrorism,'' Donald Trump said on ''Face the Nation'' after the San Bernardino shootings. ''And we have a president that won't issue the term. He won't talk about it.'' Gov. Chris Christie of New Jersey made the same point on the same show: ''They won't say radical Islamic jihadist.'' The implied question was, How can the country fight its enemies if the president won't say who they are?
John McWhorter, a linguist at Columbia University, sees the insistence of the president's critics on ''radical Islam'' as ''childish,'' given how listeners may hear it. ''In a sentence such as 'We must eradicate radical Islam,' the object of eradicate is technically 'radical Islam,' yes, but the core object, the heart of the expression 'radical Islam' is 'Islam,' '' McWhorter wrote last month on CNN.com. ''That affects how one processes such a sentence -- the adjective can come off as a kind of decoration.''
The terms ''radical Christian'' and ''radical Jew'' have little purchase, not because there aren't people who commit violence in the name of Christianity or Judaism but because they don't loom large in the public consciousness and threaten to swallow a religion's whole identity. Robert Dear, suspected of killing three people at a Planned Parenthood clinic in Colorado Springs in November, was an ''extremely evangelistic'' Christian, according to his ex-wife. Online, he wrote about Jesus. Scott Roeder, who in 2009 killed Dr. George Tiller, an abortion provider in Kansas, testified at his trial about his conversion to Christianity and said that his faith and his views about abortion went ''hand in hand.'' Yet most Americans would not equate anti-abortion violence with radical Christianity. We assume that these men are outliers -- not exemplars.
The same assumptions, in the West at this moment, are not accorded Muslims. ''It puts the onus on Muslims to prove they are not one of them,'' Jamal J. Elias, a professor of religious and South Asian studies at the University of Pennsylvania, told me over the phone. For Trump, the use of ''radical'' is a kind of entry point for blatant discrimination. We are ''at war with radical Islam,'' he said earlier this month -- defending his call to bar all Muslims abroad from entering the United States.
The use of ''radical'' has played out similarly in other moments of American history. In 1919, when he was 24, J. Edgar Hoover earned a promotion at the Department of Justice to head a new unit called the Radical Division. ''It was a time of deep concern over radical revolutionaries and terrorists supposedly pouring into the country from Italy, Russia and Eastern Europe, who also often happened to come from Catholic and Jewish backgrounds,'' says Beverly Gage, a Yale historian who is writing a biography of Hoover. In April and June 1919, two nationwide bomb plots targeted dozens of prominent businessmen and politicians, including Attorney General A. Mitchell Palmer. In response, Hoover helped engineer the Palmer raids, arresting several thousand people, most of them immigrants who belonged to anarchist and Communist groups. Congress followed by passing stringent immigration restrictions based on national origin.
And yet ''radical'' has also been a term of honor rather than contempt. If you see an urgent need for change, you may decide that reform -- working within the system -- will serve only to prop it up. The left, in particular, has often embraced that view over the last century. Opposing the Vietnam War in 1967, Martin Luther King Jr. called for the nation ''to undergo a radical revolution of values.'' It was the country's most dissent-filled decade, when feminists, labor organizers, environmentalists and student groups also unabashedly agitated for significant change. They looked to American history for intellectual forebears. ''Many of the radicals of the '60s tried to resuscitate an American tradition of resistance from the bottom up and giving voice to the powerless,'' the New York University historian Thomas Sugrue told me. ''They went back as far as the early Republic, to validate their critique and to defend grass-roots participatory democracy as essential.'' For years, the historian Eric Foner has taught a course at Columbia University called the Radical Tradition in America. Two of his former teaching assistants, Timothy McCarthy and John McMillian, edited a 2003 collection, ''The Radical Reader,'' which opens with American revolutionaries like Thomas Paine and moves to utopians like Walt Whitman, abolitionists like Frederick Douglass and suffragists like Sojourner Truth.
The 1960s radicals who advocated armed self-defense, like the Black Panthers, or turned to violence, like the Weathermen, also laid claim to deep American roots. In 1969, the Weathermen blew up a statue in Chicago built to honor the police who died during the Haymarket affair in 1886, in which the police dispersed a peaceful labor demonstration, and someone in the crowd threw a bomb. ''The statue commemorated the oppression of radicalism,'' Gage says. ''By blowing it up, the Weathermen commemorated the anarchists. They were very self-conscious about that.''
Blowing up the system is generally less appealing to conservatives, who tend to defend the status quo. But there are exceptions to that rule. ''Extremism in the defense of liberty is no vice,'' Barry Goldwater said when he accepted the Republican nomination as their party's presidential candidate in 1964. At the time, he was the hero of a newly identified ''radical right,'' epitomized by the John Birch Society, a conspiratorial anti-Communist and anti-civil-rights group with chapters throughout the nation. Mainstream conservatives set out to marginalize the Birch Society as an irresponsible fringe element. Radicals, after all, are the members of a group who push its limits and either end up leading or getting pushed out. Today Republicans in the House of Representatives who call themselves the Freedom Caucus and unseated the House speaker John Boehner last fall are nurturing the spirit of radical rebellion on the right.
In a sense, ''radical'' is a protean word, Sugrue points out, with more meanings and possibilities than we can track. But one common thread that ties radicals together is their scorn for authority outside their own movement. On the inside, the experience of radicalization is a conversion to be celebrated, when false trappings appear to fall away and a deeper truth emerges. But what if the radicals are too full of their own self-certainty? That's the danger inherent in the definition. Then, like Syed Farook and Tashfeen Malik, they turn into walking sticks of dynamite.
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