SUSAN SONTAG was the most provocative and prolific of the new wave of New York intellectuals who came to prominence in the 1960s and 1970s. Her writing during those years of enormous cultural and political change earned her the sobriquet of “the evangelist of the new”, and her polymath expertise and vocal cultural comment made her in subsequent years one of the closest equivalents in her country to the French concept of a public intellectual.

Stylistically acute and sharply perspicacious, Sontag’s writing gained much of its currency from her talent for snappy epigrammatic formulations. “Interpretation is the revenge of the critic upon art”; “In America the photographer is not simply the person who records the past, but the one who invents it”: such epithets were as engaging for the popular reader as they were debatable for academics. Almost as soon as her contentious essay Notes on Camp appeared in the Partisan Review in 1964, she became known for a theorist’s approach to popular affairs that had more in common with the philosophy and criticism of the continental thinkers she so admired than with the other American commentators of her day.

Susan Sontag was born in New York in 1933, but her mother returned to China, where Sontag’s father was a fur trader, soon after the birth. Susan and her younger sister Judith were left in the care of their grandparents until the death of their father when Susan was five. Her mother moved both daughters to Tucson, Arizona, and remarried when Susan was 12. She adopted the surname of her stepfather, Nathan Sontag.

For Sontag, childhood was “a terrible waste of time”. She was intellectually precocious, and from North Hollywood High School she moved to the University of California at 15, in 1948. After a year she transferred to the humanities programme at the University of Chicago, where she was taught by Kenneth Burke, graduating in 1951. There, aged 17, she met the sociologist Philip Rieff, whom she married ten days later.

She took two MA degrees at Harvard, in English literature and in philosophy in 1954 and 1955 respectively, before beginning a doctorate. In 1957 she won a scholarship to study at St Anne’s College, Oxford, but she soon transferred to the University of Paris, which she found more congenial. Later in life, she would spend half of each year there.

In 1959, having divorced, she moved to New York with her six-year-old son and $30. She swiftly found employment lecturing at the City College and Sarah Lawrence College, and also worked as contributing editor of Commentary, which fuelled her desire to work as a freelance writer. Between 1960 and 1964 she taught in the religious studies department at Columbia University. She also served as writer-in-residence at Rutgers after publishing her first novel, The Benefactor (1963), the heavily experimental tale of a man who, plagued by distressing dreams, resolves that they are the higher reality to which he must make his life conform and sets about doing so.

Her teenage dream of writing for Partisan Review soon came to fruition, and this brought her into close contact with the New York liberal literary scene, and Notes on Camp, the essay that established her almost instantly as a cultural commentator of stature, appeared in 1964. Couched in the aphoristic style for which Sontag would later become renowned, the essay postulated what were then such leftfield views as “the most refined form of sexual attractiveness (as well as the most refined form of sexual pleasure) consists in going against the grain of one’s sex”. Equally vilified and hailed for her championship of an emergent counterculture, Sontag later expressed surprise that an essay published in such a relatively minor journal could have excited so much popular debate: but her undeniable talent for self-promotion, coupled with her combative intellect, ensured that it did. Before long Vogue and Vanity Fair were touting the striking young woman as an American equivalent to those European stylists and commentators from whom she drew many of her principles.

In a hectic decade, Sontag published her groundbreaking collection of essays Against Interpretation (1966), the novel Death Kit (1967), Trip to Hanoi (1969) and Styles of Radical Will (1969). She won the George Polk Memorial Award in 1965 and a Rockefeller Foundation grant in 1965 (and 1974) and was made a Guggenheim Fellow in 1966 (and 1975).

Her growing reputation as a film critic had earned her a jury place at the 1967 Venice and New York film festivals, and her own film, Duet for Cannibals, was shown at the 1969 New York festival. She had a valuable impact upon experimental art in the 1960s and 1970s and few New York intellectuals can be said to have identified so acutely with the ideas of high European Modernism.

During the 1970s she began to distance herself from the radical avant-garde, but she remained much in the public eye. Stanley Aronowitz called her “the major American example of the critic as star”, but Sontag herself was properly ambivalent about this status. Part of her appeal lay in her intellectual range and her eschewing of any single party position. She lent gravitas to the imagination of popular culture and helped to bridge the chasm between the small highbrow journals and the mass media.

In 1979, for example, she told Rolling Stone that “rock’n’roll was the reason I got divorced”, and noted that her writing career had stemmed from the “total separation between the people who were tuned into popular culture and those who were involved in high culture . . . There was nobody I ever met who was interested in both, and I always was.”

She came closest to outlining an intellectual programme with her manifesto in 1964 “against interpretation”, a startling phenomenological thesis founded on existentialism. It called for an end to scholastic interpretation of art in favour of genuine sensory perception, arguing that “a work of art is a thing in the world, not just text or commentary on the world” and suggesting that criticism should judge the artistic experience itself, rather than attempting to “translate” it or extrapolate from it.

In 1977 On Photography won her the National Book Critics Circle award for criticism. “I came to realise,” Sontag said of the book, “that I wasn’t writing about photography so much as I was writing about modernity, about the way we are now. The subject of photography is a form of access to contemporary ways of feeling and thinking.” Her later treatise on photography, Regarding the Pain of Others (2003), examined how pictures of warfare were both informed by, and influenced, contemporary political and artistic concerns of those who produce the photographs, and those who in turn view them.

Throughout the 1980s she was a regular speaker at international writers’ conferences, and as president of PEN, 1987-89, she was one of the chief supporters of Salman Rushdie when his life was threatened after the publication of The Satanic Verses. In 1993 she published her first play, Alice in Bed, and her fourth novel, In America, appeared in 1999.

Sontag’s political writings caused considerable public controversy. Impelled, she said, by grief, she wrote on America’s involvement in Vietnam, on Cuba, communism and the wars in Yugoslavia. She valued Hanoi and China, in particular, as sensibilities alternative to that of the West. At a 1982 rally for Polish Solidarity in New York, she famously declared communism to be “Fascism with a human face”, which was widely but erroneously read as a conversion to the Right. Her political activism and concern for human rights also took her to Yugoslavia in the early-1990s, where she called for international intervention to put an end to the erupting civil war there.

In one of her best works, Illness as Metaphor (1978; expanded into Aids and its Metaphors, 1989), Sontag warned against the tendency to regard illness metaphorically, and wrote that the healthiest way of being ill is the one most devoid of the figurative. Some of her best insights in the book perhaps stemmed from her own fight against cancer, which was first diagnosed in 1975.

Susan Sontag is survived by her son.

Susan Sontag, author and activist, was born on January 16, 1933. She died of cancer on December 28, 2004, aged 71.