Susan Sontag, who died yesterday at the age of 71, was a contentious essayist and novelist, best known for her cultural criticism, which ranged widely from discussions of literary masterpieces to analysis of popular culture.

Her essays “Against Interpretation,” “Notes on ‘Camp,'” “The Imagination of Disaster” (her anatomy of science fiction movies), and her books “On Photography” and “Illness as Metaphor” are likely to be her main legacy to American literature, although she produced one best-selling novel, “The Volcano Lover,” and a second novel, “In America,” won the National Book Award.

Sontag died at Memorial Sloan-Kettering Cancer Center in Manhattan of complications of acute myelogenous leukemia, her son told the Associated Press.

Sontag had been treated for a particularly virulent form of breast cancer in the 1970s and not only survived but went on to write about the disease in “Illness as Metaphor,” a bold attack on the mystique surrounding sickness. She argued for the patient’s right to seek out aggressive treatment, second opinions, and above all to treat illness as just that – not a psychological malady that the patient was somehow responsible for, but an illness that could be treated openly without shame. As a result of Sontag’s book, patients began exerting more control over their medical conditions, and medical schools assigned her book as a primer on how to deal with patients and their illnesses.

“Notes on ‘Camp,'” part of her provocative 1966 essay collection, “Against Interpretation,” showed off her range and her claims to originality. Although the word “camp” had been described in a “lazy two-page sketch” by Christopher Isherwood, Sontag offered a taxonomy of the term. Camp was corny and flamboyant, extravagant and stylized. The camp sensibility constituted an aesthetic – the admiration of style in and for itself. Figures such as Greta Garbo, Jayne Mansfield, Mae West, and the “public manner of rhetoric of de Gaulle” were “pure camp,” Sontag argued. Camp was important, Sontag concluded, because it cut across all categories of art and formed one sensibility that is “pluralistic,” one that appreciates the “beauty of a machine” as much as a painting by Jasper Johns, a film by Godard, or a Beatles song.

Time magazine took Sontag up as the intellectual flavor of the week. Still, she remained on top, so to speak, photographed by the best photographers of her day. Her jacket photographs had the aura of French film noir. Her status as a pop icon was singled out in “Contemporary Biography,” which called her “The Natalie Wood of the U.S. avant garde.”

Sontag’s supporters hailed her eclecticism and saw her work as bridging the gap between popular and elite culture. Whereas an earlier generation of critics worried that mass culture would inundate and drive out the highest art, Sontag seemed to embrace all forms of art. Later, when college courses made popular culture a legitimate discipline of study, and television seemed to obliterate much of the audience for high culture, Sontag retreated to a culturally conservative position barely distinguishable from that of Matthew Arnold, the Victorian-era arbiter of high culture whom she had once high-handedly dismissed.

But Sontag did not repudiate her early work so much as she waved it away as the writing of a young enthusiast unable to foresee the consequences of her theorizing. The older Sontag said, “I’ve come to appreciate the limitations – and the indiscretion – of generalizing either the aesthete’s or the moralist’s view of the world without a much denser notion of historical context.” Still later, she confessed, “I was not being entirely honest with myself in the 1960s.”

Sontag’s model of the intellectual was the Romanian philosopher E. M. Cioran. Her essay on his work, which appeared in her influential second essay collection, “Styles of Radical Will” (1969), was entitled “Thinking Against Oneself”- an apt phrase for Cioran’s neo-Hegelian notion that, in Sontag’s words, “It is the destiny of every profound idea to be quickly checkmated by another idea, which it itself has implicitly generated.” Contradictions were almost a matter of pride with her, not a legacy to live down.

During the Vietnam War, Sontag took an activist, dissident stance, writing long essays like “Trip to Hanoi,” which reflected her shame over being part of an American empire she saw as destroying the hearts and minds of the very people the U.S. administration wished to win over. Whereas Sontag’s literary and cultural essays were sophisticated and nuanced, her political writings were strident, strewn with epithets and calls to action like “Viva Fidel!” Although she later recanted such simple-minded leftism, she was never able to complete the political essay that was meant to answer her critics. Having abandoned the left, she had nowhere to go, and took refuge in dismissing political labeling.

Nonetheless, Sontag’s political activism continued. She supported American involvement in the Balkans – indeed, she risked her own life directing a production of “Waiting for Godot” in Sarajevo even as the city was being shelled in 1993. But she opposed the second Iraq war, arguing that America’s vital security interests were not threatened by Saddam Hussein’s regime.

About 9/11, Sontag wrote in the New Yorker, “Whatever may be said of the perpetrators of Tuesday’s slaughter, they were not cowards.” Her comments provoked outrage, especially when she added that Americans ought to stop talking about the event in psychological hand wringing terms.

As President of American PEN, Sontag campaigned tirelessly for Salman Rushdie during the period of a fatwa that put his life in danger. And she remained active throughout her career working to save the lives of writers imprisoned unjustly or faced with execution.

Sontag’s best work, however, always took place at one remove from reality.

“On Photography” (1977), arguably her most important contribution to American letters, is a probing discussion of the nature of photography. Her first essay, “In Plato’s Cave,” is a kind of precis for the book. She plays with the philosopher’s fable of knowledge: the setting of a cave in which the only knowledge possible is what is seen in the reflections on a wall. That is to say, human knowledge of the world is secondhand, a reflection of the truth, not truth itself – a copy, not the original. St. Paul’s statement that we see as through a glass darkly constitutes a similar comment on the human inability to see clearly, to grasp the whole of existence, let along the divinity of God (St. Paul), or the perfect world of ideas posited by Plato. Thus Sontag’s opening sentence carries moral, aesthetic, and almost religious connotations: “Humankind lingers unregenerately in Plato’s cave, still reveling, its age-old habit, in mere images of the truth.”

Photographs, which can look so real, so much a part of the world, are deceptive, Sontag cautioned. Whereas photography seems a way to collect and to encompass the world, it is also a way of fragmenting it into a series of shots-images that have no narrative thread. Instead of integrating the world, photographs atomize it.

Like so much of Sontag’s writing, “On Photography” incited a maelstrom of support and criticism. Photographers accused her of attacking their art. But Sontag, who made her fondness for photography well known, saw herself as again “thinking against oneself,” questioning the premises of what she liked.

Although Sontag behaved like a native New Yorker and was in fact born in New York City, she spent her early years in Arizona and California. Born Susan Rosenblatt, she grew up alienated from her alcoholic mother and dreaming wistfully of her father, who died while on a business trip in China when she was 5.

A precocious student at Hollywood High School, she graduated when she was 15, and after a semester at Berkeley attended the University of Chicago, where she met and married sociology instructor Philip Rieff. Sontag revealed little about these early years, although they are treated obliquely in her short story collection, “I, etcetera” (1978).

Married at 17 to Rieff, and a mother shortly after that, Sontag put her dreams of becoming a writer on hold as she earned graduate degrees in literature and philosophy and began teaching at the University of Connecticut, City College, Columbia University, and other schools.

Sontag divorced Rieff in 1959 – in part because she found herself attracted to women and wanted to live unconstrained by marital or institutional ties – and began work on a first novel, “The Benefactor,” which Farrar, Straus & Giroux published in 1963. Receiving mixed reviews for a work that critics deemed derivative of the French new novel, Sontag struck intellectual nerves with her essay collections, even though with “Death Kit” (1967) she tried once more to establish her presence as a novelist.

Sontag would later dismiss these early novels as apprentice work, but her publisher was careful to keep all of her work in print, an extraordinary fact in a day when even writers such as Norman Mailer and John Updike regularly find parts of their oeuvre shoved off the publisher’s backlist.

By the late 1960s, Sontag had forsaken regular academic employment, decided not to complete her Ph.D., and returned to the academy only for guest lectures and writer-in-residence appointments. She became the public intellectual extraordinaire – the critic whom other writers loved to quote, the critic who showed up as a “name” in films like “Gremlins 2” and “Bull Durham,” in which Kevin Costner opines: “The novels of Susan Sontag are self-indulgent, overrated crap,” to which Susan Sarandan replies, “I think Susan Sontag is brilliant.” She was one of Woody Allen’s interview subjects in “Zelig.”

Sontag was always a good subject for debate. She was a provocateur and a gadfly. At her most sedate, in novels like “In America,” she could be as boring as any second-rate historical novelist. But at the top of her form she energized public discussion and made generations of readers understand how deeply ideas matter.

Susan Sontag

Born January 16, 1933, at New York City; died December 28, 2004, at Memorial Sloan-Kettering Cancer Center in Manhattan; her marriage to Philip Rieff ended in divorce in 1959; survived by her son David Rieff.