The Federal Bureau of Investigation didn’t know what to do about Dorothy Day. It was 1941, and Director J. Edgar Hoover was concerned about Day’s onetime communism, sometime socialism, and all-the-time anarchism. After months of investigating—interviewing her known associates, obtaining her driving record and vital statistics, collecting her clips from newspaper morgues, and reviewing the first of her autobiographies, “From Union Square to Rome” (“an interesting, running account of the life of the authoress”)—the F.B.I. decided that the subject of Bureau File 100-2403-1 would not need to be detained in the event of a national emergency. Day would have disagreed with them: not because she felt she was dangerous but because she knew that the nation was already in an emergency, and had been for some time.

The emergency was poverty, and Day had been alarmed by it her whole life. She first encountered it in the slums of Chicago, where she lived as a teen-ager, and she saw it all around her in New York City, where she moved after dropping out of college, and lived for more than six decades. Even before the Great Depression, Day had been sensitive to the plight of the poor, a sensitivity that ultimately shaped her calling. At thirty, she converted to Catholicism. In the years that followed, she started a radical newspaper and began opening what she called “houses of hospitality” for those who needed something to eat and somewhere to stay.

Eventually, Day’s Catholic Worker Movement would serve the poor in more than two hundred communities. Under her guidance, it would also develop a curiously dichotomous political agenda, taking prophetic stands against racial segregation, nuclear warfare, the draft, and armed conflict around the world, while opposing abortion, birth control, and the welfare state. That dichotomy seems especially stark today, when most people’s beliefs come more neatly packaged by partisan affiliation. But by the time she died, in 1980, Day had become one of the most prominent thinkers of the left and doers of the right. In her lifetime, it was the secularists—including Dwight Macdonald, in a two-part Profile published in this magazine, in 1952—who called Day a saint. Now, though, the cause of her sainthood is officially advancing within the Catholic Church, a development that has occasioned a new biography and a documentary, both of which explore the contentious question of who owns her legacy.

She wasn’t sure if she was afraid of God or the ground, but the nightmares Dorothy Day had as a child featured a noise that got louder and nearer until she woke up sweaty and terrified. She had been born in New York, in 1897, but her family relocated to California in 1904, and they were living in Oakland two years later, when the San Francisco earthquake struck. That tragedy changed Day’s life in two ways. First, it affirmed her preëxisting fears about annihilation, while simultaneously stirring in her a theory of mercy based on her mother’s nightly reassurances and the broader response of collectivity and charity. Why, she wondered, couldn’t the community care for all its members so generously the rest of the time? The second change was more pragmatic: her father, John, was a sportswriter who could barely support his wife and five children on his salary, so when the earthquake destroyed the press that printed his newspaper he moved the family again, this time to Chicago.

John and Grace, his wife, had been married in a church, but they never took their children to worship. Even so, Dorothy, their middle daughter, was a pious child who read Scripture as ravenously as novels and watched with interest as her friends and their families prayed. At twelve, she demanded to be baptized at a nearby Episcopal church; in high school, she learned Greek and practiced her translation skills on the New Testament. She tested her way into a scholarship at the University of Illinois, where she matriculated not long after the socialist Eugene Debs got nearly a million votes in the 1912 Presidential election. Like many other students, she was drawn to the college Socialist Club, which is where she heard a lecture by Rose Pastor Stokes, a feminist who went on to help found the Communist Party of America.

Politics change like the weather, and this era of falling atmospheric pressure is nicely captured in “Dorothy Day: Dissenting Voice of the American Century,” a new biography co-written by John Loughery and Blythe Randolph. It was the great age of “isms,” especially on American campuses, and at first Day enthusiastically embraced them. Her family had always been financially marginal, and that left her receptive to all politics that prioritized the poor; at the same time, a rising atheism and anti-authoritarianism left her eager to cast off her religious faith, which her comrades regarded as risible. She joined a literary club called the Scribblers and submitted work to a magazine and a newspaper on campus, along with the local paper in Urbana–Champaign. Her writing was more impressive than her grades, which included an F in biology, so, when her family moved back to New York, Day dropped out and went with them.

Day’s father had helped her brothers find journalism jobs, but he refused to help her, so she was left to knock on the doors of papers around the city. When that failed, she remembered the alternative media and leftist publications she had learned about on campus, and found a job with the Call, a socialist daily in which her first byline appeared under the headline “Girl Reporter, with Three Cents in Her Purse, Braves Night Court.” A few weeks later, she interviewed Leon Trotsky, who was then living in the Bronx. After that, she managed to craft a feature from a three-minute conversation with Margaret Sanger’s sister, newly released from prison and desperate to drum up support for the American Birth Control League.

In between writing for every radical outlet in town, Day palled around with Marxists, got arrested for picketing the White House with the suffragists, and took a billy club in the ribs at an antiwar riot. “Bohemian” doesn’t begin to describe Day’s life in this period. Her drinking was legendary, even by Greenwich Village standards; the literary critic Malcolm Cowley claimed, in his memoir, that Day could hold her liquor better than most gangsters. Some of that drinking took place during Prohibition, and was thus illegal, and much of it took place at a bar alternately known as the Hell Hole and the Bucket o’ Blood. Day’s friends were all writing books or appearing in them, and she was said to be the model for characters in “The Malefactors,” by her onetime roommate the novelist Caroline Gordon, and in “A Moon for the Misbegotten,” by her onetime lover the playwright Eugene O’Neill.

Day herself wrote a book during this time: an autobiographical novel called “The Eleventh Virgin,” published in 1924. It told the story of a disastrous affair she’d had with an older writer, which ended after she attempted suicide and had an illegal abortion, a procedure performed by an ex-boyfriend of the anarchist Emma Goldman. Day wrote the novel while honeymooning in Europe with a different man. The rebound ended no better than the previous relationship: one morning, Day took off her wedding ring, left it on the bureau, and walked out of the marriage.