Dr. Daly emerged as a major voice in the burgeoning women's movement with her first book, "The Church and the Second Sex," published in 1968, and "Beyond God the Father: Toward a Philosophy of Women's Liberation," which appeared five years later. That accomplishment was viewed, then and now, as all the more significant because she wrote and taught at a Jesuit college.
"She was a great trained philosopher, theologian, and poet, and she used all of those tools to demolish patriarchy -- or any idea that domination is natural -- in its most defended place, which is religion," said Gloria Steinem.
Dr. Daly, whose relationship with Boston College grew tempestuous as she insisted that only women could take her classes, died Sunday in Wachusett Manor nursing home in Gardner. She was 81 and her health had failed in the past few years, including recent paralysis due to a neurological condition.
" 'The Church and the Second Sex' was every bit as important in the Catholic world as Betty Friedan's 'The Feminine Mystique,' " said James Carroll, an author and columnist for the Globe's opinion pages who formerly was a Catholic priest.
Sister Joan Chittister, a feminist author and a member of the Benedictine Sisters of Erie, Pa., said Dr. Daly "literally turned the standard theological concepts upside down. Mary played with language in such a way that you simply had to stop and think. ... You couldn't use old words in the old ways."
Coining words with an Irish wit that could slip from sly to savage, Dr. Daly dismissed college officials as "bore-ocrats" who suffered from "academentia" and "predictably reacted with 'misterical' behavior" -- all in a 1996 autobiographical article for The New Yorker magazine. But beyond her choices to capitalize certain words and remold others like clay, she was deeply serious about language and the way it shapes a sense of self.
"Ever since childhood, I have been honing my skills for living the life of a Radical Feminist Pirate and cultivating the Courage to Sin," she wrote in the opening of "Sin Big," her New Yorker piece. "The word 'sin' is derived from the Indo-European root 'es-,' meaning 'to be.' When I discovered this etymology, I intuitively understood that for a woman trapped in patriarchy, which is the religion of the entire planet, 'to be' in the fullest sense is 'to sin.' "
Dr. Daly's career at BC, where she joined the theology department faculty in 1966, ultimately ended over what administrators, and many public commentators, saw as her sin of exclusivity. After the college went co-ed in the early 1970s, she only allowed women to take her classes, teaching a few men privately over the years.
She said the presence of men clouded the learning environment, and that a women-only classroom fell within the bounds of academic freedom.
"If a man were in the class he would be very likely to say, 'Oh, no. I am oppressed too.' ... He would say, 'I can't cry. I'm not allowed to express myself, wah, wah,' " she told the Globe in 1999.
The dispute spilled into the courts in the late 1990s when a male student hired a lawyer after Dr. Daly bared him from her class. The college tried to force her into retirement and she sued, claiming breach of contract.
In previous years, Dr. Daly had successfully fought BC's attempt to deny her tenure. This time, she and the college reached a settlement in 2001 and, at 72, she agreed to retire.
Those who knew Dr. Daly and her work, however, say the acrimonious dispute didn't diminish her contributions to feminist philosophy.
"I think she was a central figure for the feminist movement in the 20th century, and hopefully beyond," said Robin Morgan, who edited Sisterhood is Powerful: An Anthology of Writings From the Women's Liberation Movement." "She had a fierce intellect and an uncompromising soul that sometimes gave even her most loving friends indigestion, but it was worth it. She redefined the parameters of philosophy. She called herself a feminist philosopher, and she really was -- she was the first.''
Chittister said: "Her legacy is a cloud of women witnesses and male theologians, too, who have now been released into whole new understandings of what the tradition really holds and really means for all of us, male and female. She was a great thinker, she was a great icon. She will be maligned by some, but history will see her very differently."
Dr. Daly grew up in Schenectady, N.Y., where her father was a traveling salesman, selling ice cream freezers. She wrote in The New Yorker that her mother, who "had been 'yanked out' of high school during her sophomore year," encouraged her to find a life outside the realm of housework.
Though she found academia generally inhospitable to a woman who wanted to study theology in the 1950s, she graduated from the College of Saint Rose in Albany, N.Y., with a bachelor's degree, received a master's in English at Catholic University of America in Washington, D.C., and a doctorate in religion from St. Mary's College at the University of Notre Dame in Indiana.
Teaching a few years left her unfulfilled, so she went to the University of Fribourg in Switzerland, from which she received four more graduate degrees in philosophy and theology.
"I was getting ready to Sin Big," she wrote in The New Yorker.
Her other books included "Gyn/Ecology, the Metaethics of Radical Feminism" (1978), "Pure Lust: Elemental Feminist Philosophy" (1984), and "Websters' First New Intergalactic Wickedary of the English Language," which she called "a dictionary for Wicked women" that she wrote with Jane Caputi in 1987.
One of Dr. Daly's caregivers was reading to her from the "Wickedary" when she died Sunday.
"She basically fairly clearly defined the outer limits of radical feminist theology," said Robert Daly, who chaired the theology department during much of Dr. Daly's tenure and was not related to her. "People around the world are generally grateful for her having done that."
An only child, Dr. Daly had no immediate survivors. Friends plan to schedule a memorial service, but noted that she had her own ideas of how her death should be marked.
"It was Mary's wish that if women or people want to memorialize her in any way they should stay in their own locality and have a get-together where they read or discuss her work," said Linda Barufaldi of San Diego, one of several former graduate students of Dr. Daly's who cared for her as her health declined.
Said Steinem: "In the way that painters and artists become more valuable after they're gone, I hope Mary will be kept alive by people going to her work."