"I love to read the way people love to watch television," she told Rolling Stone. For her, culture was a vast smorgasbord, a movable feast. The point, she often said, quoting Goethe, was "to know everything."
Sontag devoted herself to demolishing "the distinction between thought and feeling, which is really the basis of all anti-intellectual views: the heart and the head, thinking and feeling, fantasy and judgment. Thinking is a form of feeling; feeling is a form of thinking."
Her quest was admired by such writers as Elizabeth Hardwick, a founder of the New York Review of Books, whose editors quickly embraced Sontag. In her introduction to "A Susan Sontag Reader," Hardwick called her "an extraordinarily beautiful, expansive, and unique talent."
Each of Sontag's essays, Hardwick wrote, "has a profound authority, a rather anxious and tender authority — the reward of passion. The tone of her writing is speculative, studious and yet undogmatic; even in the end it is still inquiring."
Others were less impressed. John Simon accused Sontag of "a tendency to sprinkle complication into her writing" and of tossing off "high-sounding paradoxes without thinking through what, if anything, they mean." Greil Marcus called her "a cold writer" whose style was "an uneasy combination of academic and hip pedantic, effete, unfriendly." Walter Kendrick found her fiction "dull and derivative."
In 1976, at 43, Sontag discovered she had advanced cancer in her breast, lymphatic system and leg. She was told she had a one-in-four chance to live five years. After undergoing a radical mastectomy and chemotherapy, she was pronounced free of the disease. "My first reaction was terror and grief. But it's not altogether a bad experience to know you're going to die. The first thing is not to feel sorry for yourself."
She learned as much as possible about the disease and later wrote "Illness as Metaphor," an influential essay condemning the abuse of tuberculosis and cancer as metaphors that transfer responsibility for sickness to the victims, who are made to believe they have brought suffering on themselves. Illness, she insisted, is fact, not fate. Years later, she would extend the argument in the book-length essay "AIDS and Its Metaphors."
An early and passionate opponent of the Vietnam War, Sontag was both admired and reviled for her political convictions. In a 1967 Partisan Review symposium, she wrote that "America was founded on a genocide, on the unquestioned assumption of the right of white Europeans to exterminate a resident, technologically backward, colored population in order to take over the continent."
In her rage and gloom and growing despair, she concluded that "the truth is that Mozart, Pascal, Boolean algebra, Shakespeare, parliamentary government, baroque churches, Newton, the emancipation of women, Kant, Marx, Balanchine ballets, et al., don't redeem what this particular civilization has wrought upon the world. The white race is the cancer of human history; it is the white race and it alone — its ideologies and inventions — which eradicates autonomous civilizations wherever it spreads, which has upset the ecological balance of the planet, which now threatens the very existence of life itself."
Considering herself neither a journalist nor an activist, Sontag felt an obligation as "a citizen of the American empire" to accept an invitation to visit Hanoi at the height of the American bombing campaign in May 1968. A two-week visit resulted in a fervent essay seeking to understand Vietnamese resistance to American power.
Critics excoriated her for what they regarded as a naive sentimentalization of Vietnamese communism. Author Paul Hollander, for one, called Sontag a "political pilgrim," bent on denigrating Western liberal pluralism in favor of venerating foreign revolutions.
That same year, Sontag also visited Cuba, after which she wrote an essay for Ramparts magazine calling for a sympathetic understanding of the Cuban Revolution. Two years later, however, she joined Peruvian novelist Mario Vargas Llosa and other writers in publicly protesting the regime's harsh treatment of Heberto Padilla, one of the country's leading poets. She also denounced dictator Fidel Castro's punitive policies toward homosexuals.
Ever the iconoclast, Sontag had a knack for annoying both the right and the left. In 1982, in a meeting in Town Hall in New York to protest the suppression of Solidarity in Poland, she declared that communism was fascism with a human face. She was unsparing in her criticism of much of the left's refusal to take seriously the exiles and dissidents and murdered victims of Stalin's terror and the tyranny communism imposed wherever it had triumphed.
Ten years later, almost alone among American intellectuals, she would called for vigorous Western — and American — intervention in the Balkans to halt the siege of Sarajevo and to stop Serbian aggression in Bosnia and Kosovo. Her solidarity with the citizens of Sarajevo prompted her to make more than a dozen trips to the besieged city.
Then in the aftermath of the Sept. 11, 2001, terrorist attacks, Sontag offered a bold and singular perspective in the New Yorker. "Where is the acknowledgment that this was not a 'cowardly' attack on 'civilization' or 'liberty' or 'humanity' or 'the free world' but an attack on the world's self-proclaimed superpower, undertaken as a consequence of specific American alliances and actions?" She added, "In the matter of courage (a morally neutral virtue): Whatever may be said of the perpetrators of Tuesday's slaughter, they were not cowards."
She was pilloried by bloggers and pundits, who accused her of anti-Americanism.
Sontag had never been so public as she became over the next three years, publishing steadily, speaking constantly and receiving numerous international awards, including Israel's Jerusalem Prize, Spain's Prince of Asturias Award for the Arts, and Germany's Friedenspreis (Peace Prize). Upon accepting the prize from Jerusalem's mayor, Ehud Olmert, Sontag said of Israel's policies toward the Palestinians: "I believe the doctrine of collective responsibility as a rationale for collective punishments [is] never justified, militarily or ethically. And I mean of course the disproportionate use of firepower against civilians."
Last March, she was found to have a condition that, if left untreated, would be fatal: a pre-acute leukemia that doctors concluded was a consequence of the chemotherapy she had undertaken to rid herself of a uterine sarcoma discovered five years before. A little more than four months after the diagnosis, she received a partial bone marrow transplant.
In an interview for the Paris Review, in 1995, Sontag was asked what she thought was the purpose of literature.
"A novel worth reading," she replied, "is an education of the heart. It enlarges your sense of human possibility, of what human nature is, of what happens in the world. It's a creator of inwardness." She was the cartographer of her own literary explorations. Henry James once remarked, "Nothing is my last word on anything." For Sontag, as for James, there was always more to be said, more to be felt.
She is survived by her son, David, and a sister, Judith Cohen.
Her papers — manuscripts, diaries, journals and correspondence — as well as her 25,000-volume personal library were acquired by the UCLA Library in 2002 and will be housed in the Charles E. Young Research Library Department of Special Collections.