She's not a brass-knuckled political figure, a Birkenstock-wearing Amazon or a breaker of corporate glass ceilings; she's just a sassy single girl in New York City. So why am I so sure that Carrie Bradshaw – the charming, ever-hopeful star of the longrunning HBO series and hit film, all based on Candace Bushnell's New York Observer column – is an icon and did as much to shift the culture around certain women's issues as real-life feminist groundbreakers?

I have written before about how radical it was that the narrative of Sex and the City centred not around a couple – let alone the traditional formula of hero-plus-beautiful-secondary-love-interest. Rather, the core of the tale was always the life-sustaining friendship among four women, as the men in their lives came and went. This break from narrative norms was remarkable not just because Bushnell was insisting that four women – no longer in their first youth – were renewably compelling on their own terms; it was also radical because, in a very un-PC but admirable flouting of feminist norms, Bushnell was brave enough to lay bare the secret – that for many women the search for love is the same urgent, central, archetypal quest story that for men is played out in war narratives and adventure tales. Bushnell was gutsy enough to disclose that even we serious, accomplished, feminist women spend a lot of time, when we are alone with our female friends, telling stories centred on the men with whom we are romantically entangled, exploring the quality of the love and attraction, the romance and the sex. And we are often just that graphic and hopeful and vulnerable and slutty as those four characters.

This was so startlingly un-sayable that when women watched Sex and the City, it was like seeing a secret set of their own dramas spring into art. Now they are the stalest of cliches, but when, in the first 1998 episode, in the midst of all that big hair and weird brown lipstick, you hear Carrie first describe the allure and disappointment of "toxic bachelors", when Samantha first says frankly that she likes to have sex without emotion, to "fuck like a man", it was bitingly fresh for women to speak these aphorisms out loud, in public, and in fabulous heels.

But there are other reasons that the characters of Sex and the City endured as icons throughout the first decade of the 21st century, and other reasons that Carrie will continue to resonate. She was a writer who arrived in the big city to test her mettle and realise her voice. Male writers have structured stories around exactly this character from F Scott Fitzgerald to JD Salinger to Philip Roth; but Carrie showed audiences week after week that a lively female consciousness was as interesting as female sexuality or motherhood or martyrdom – the tradition role model options.

Carrie is a writer, and her adventures aren't just love escapades as they would be for a Fanny, or even an Elizabeth Bennet: they are material filtered though one woman's distinctive point of view and crafted into text in her unique voice. After the shallow or deeper sagas of hot sex or social slights, of hungover breakfasts with the girls or Cosmopolitans and hookups at night, every episode saw the letters unscrolling – often forming quite existential questions – across Carrie's computer screen. Teenage girls watching each episode were taking in a clear message. Not only can I dress up and flirt, seduce and consume, overcome challenges, yield to temptations, take risks, fail, try again – I can think about it all, and what I think will matter.

It may seem ironic that the first female thinker in pop culture (not in books – books have had them since Doris Lessing) came to us with corkscrew curls and wacky cloth flowers in her hair, teetering on Manolos worn over Japanese-schoolgirl socks. But really, can you name a TV show or film prior to this that centred around a woman reflecting about her life and the world? Carrie, for better or worse, was our first pop-culture philosopher.

What about other firsts from Sex and the City that made a big difference in women's lives, and probably, by extension, men's lives too? Let's just take a look at Samantha. The history of English – and one might say western – culture, when it comes to female sexuality, is the history of sluts getting punished for their lust.

From the teenage non-virgins stoned to death in the Bible, to Hester Prynne and Madame Bovary, sluts always, but always, get some terrible disfiguring disease – or die. They are always object lessons to women reading or watching that they can't get away with it – if it is sexual autonomy and self-expression. Erica Jong will always be a personal heroine of mine because her alter ego, Isadora Wing in Fear of Flying, broke that convention so decisively. But again, books are not enough. In TV or film, do you get to be a slut without comeuppance? Never. Yet there is Samantha, bawdy as the Wife of Bath, always cheerfully horny and materialistic, utterly without Calvinic redeeming qualities, living at last with her devoted younger boy toy in LA in the Sex and the City movie – finally leaving him because she is just not cut out to mix her driving, unmediated sexual energy with commitment. Did not thousands of young women eager to explore their sexuality, but scared of being labeled sluts by their peers, breathe a sigh of relief or even liberation watching Samantha down another tequila, unrepentantly ogle the sex god at the end of the bar, and get richer and more beautiful with age, with no STDs or furies pursuing her? Charlotte and Miranda are fine, as they go – stereotypes of the good girl and the restless corporate achiever. But Carrie, and then Samantha? A revolution.

Oddly enough, as I was getting ready to write this, I stepped into a restaurant in New York – and in brushed a woman in big sunglasses and crazy boots, who warmly greeted the staff in a manner so familiar to me I smiled instinctively. I thought it must be a friend of mine. Well, I wasn't completely wrong. Actually, it was Sarah Jessica Parker, a stranger. Yet every woman in the room reacted with a similar happy, gut familiarity.

Why? Not because of the actor – because of the character.

Because we had all heard Carrie's stories from our own girlfriends, and recognised in her something of our best selves. Hey girlfriend!

• This article was amended on 26 February 2010 to correct a previous amendment. The original included some references to Sex In the City. This title has been corrected.