Isadora Duncan was the original California girl, a free spirit from San Francisco whose bohemian beliefs revolutionized dance. She believed in bare feet, comfy clothing, the sacredness of sunshine and ocean waves. She believed her body was her temple. She believed in free love and good music. She hated ballet.

Though she died when the century was still young, Duncan remains a timeless emblem of rebellion. Her reform of the dance world was so complete, and so right, that in the decades since no one has come along to match her influence. Certainly, there have been many in the 20th century who have altered the form, taken it in startling new directions, created new ways of moving, changed our ways of seeing. In fact, dance in this century has been all about change. Yet all of the innovators--Michel Fokine, Martha Graham, George Balanchine, Antony Tudor, Merce Cunningham, to name just a few--owe something to Duncan. At a time when dance was considered a lesser art form, she insisted that dance was important--on a par with music, painting, sculpture and poetry.

Duncan didn't develop a new technique or invent steps. We know little of her choreography. None of her works exists on film. When she died in 1927--strangled by one of her long scarves as it caught in a wheel of her car--most of her works died with her. Few performers carried on Duncan's particular type of dancing after her death; her style was so personal that it could only be imitated, not expanded upon. But what she did leave behind was a changed outlook on dance.

Her achievement, as choreographer Agnes de Mille put it, was a point of view.

Duncan didn't really discover anything new except an attitude. Before Duncan, dance adhered to a formula. Afterward, it became a tool of self-expression. Dance had declined into an artless frivolity before Duncan spoke up about it. Afterward, it was taken seriously as an art form.

Duncan peeled away the artifice and excesses that had cluttered concert dance, namely ballet. She denounced ballet's restricted, codified technique, its unchanging recipe of components (three acts, inscrutable pantomime, showy technical tricks, assorted pageantry), its unrealistic story lines, its reliance on spectacle and its pandering to the egos of its stars.

"The dance was once the most noble of all arts," she wrote, "and it shall be again."

At the end of the 19th century, European ballet had become an exercise in titillating the male audience--the well-dressed leerers, immortalized in Degas' paintings, who came to gawk at the girls in their increasingly short skirts. Duncan centered her dance on subjects like love, loss and motherhood. Issues that meant something--especially to other women, who were her most ardent fans.

She preached a return to natural movement, which is why she kicked off her slippers, slipped out of her corset and petticoat and danced in a loose Grecian tunic. She indulged in her own relaxed, idiosyncratic style, with emphasis on the fluidity of the arms and swoop of the upper body. Her lines were curvy, undulating--she was inspired by the rhythm of the waves--as opposed to ballet's rigidly upright posture. She introduced natural, unaffected running and walking. She was also frequently still.

Just as she stripped her person of the ornate attire of the Victorian era, she stripped the stage of scenery and props. The Duncan experience was an unadorned body on an unadorned stage, moving to the music of such eminent classical composers as Beethoven, Schubert and Chopin.

Duncan was a resolutely unconforming artist who didn't give a damn about tradition--and created a model for legions of artists since to follow. She was a flamboyant character who lived a life of open and unabashed scandal, bearing three children out of wedlock. She delighted in defying social convention. She was a feminist and a Darwinist. As a high-profile supporter of women's rights and of the Russian Revolution, she became a magnet for left-wing intellectuals. She was, in short, an advocate for all kinds of personal and political freedoms, at a time when the struggles for such freedoms were bubbling to the surface. Though during her lifetime she achieved her greatest fame in Europe, she was the prototypical modern American--the individual rising above society.

While she's rightfully seen as the mother of modern dance, the originator of the break with ballet, the irony is that though Duncan had sought to demolish ballet, she ended up enriching it and ensuring its continued success.

Her dances to Chopin moved Russian choreographer Fokine to institute his own reforms. He stuck to basic ballet technique but, after seeing Duncan perform, he began incorporating a greater freedom of the upper body. He broke from the three-act formula, creating short, concentrated one-act ballets like "Les Sylphides" and used sophisticated classical music instead of the commonplace scores that had become popular in ballet. Fokine's influence, in turn, spread to George Balanchine, to Frederick Ashton and throughout modern ballet.

During the latter half of the 19th century, critics complained that ballet had debased itself with acrobatics and music-hall crudeness. Technical feats--pirouettes, jumps and whipping turns on one foot, or fouettes--were valued over artistry. Yet one can point to the same faults in much of dancing today--the emphasis on technique above all else, the flaunting of physical ability over individual expression. We're due for another voice like Duncan's, to sweep away the froufrou and the fabulousness, and return to dance its primal power.