There is a moral panic in America over young women's sexuality – and it's entirely misplaced. Girls "going wild" aren't damaging a generation of women, the myth of sexual purity is. The lie of virginity – the idea that such a thing even exists – is ensuring that young women's perception of themselves is inextricable from their bodies, and that their ability to be moral actors is absolutely dependent on their sexuality. It's time to teach our daughters that their ability to be good people depends on their being good people, not on whether or not they're sexually active.

A combination of forces – our media- and society-driven virginity fetish, an increase in abstinence-only education and the strategic political rollback of women's rights among the primary culprits – has created a juggernaut of unrealistic sexual expectations for young women. Unable to live up to the ideal of purity that's forced upon them in one aspect of their lives, many young women are choosing the hypersexualized alternative that's offered to them everywhere else as the easier – and more attractive – option.

More than 1,400 purity balls, where young girls pledge their virginity to their fathers at a prom-like event, were held in 2006 (the balls are federally funded). Facebook is peppered with purity groups that exist to support girls trying to "save it." Schools hold abstinence rallies and assemblies featuring hip-hop dancers and comedians alongside religious leaders. Virginity and chastity are re-emerging as a trend in pop culture, in our schools, in the media, even in legislation. So while young women are subject to overt sexual messages every day, they're simultaneously being taught their only real worth is their virginity and ability to remain "pure."

So what are young women left with? Abstinence-only education during the day and Girls Gone Wild commercials at night. Whether it's delivered through a virginity pledge or by a barely dressed tween pop singer writhing across the television screen, the message is the same: A woman's worth lies in her ability – or her refusal – to be sexual. And we're teaching American girls that, one way or another, their bodies and their sexuality are what make them valuable. The sexual double standard is alive and well, and it's irrevocably damaging young women.

I started to see the myth of sexual purity everywhere. Whether it appears in a story about a man killing his girlfriend while calling her a whore or in trying to battle conservative claims that emergency contraception or the HPV vaccine will make girls promiscuous, the purity myth in America underlies more misogyny than most people would like to admit.

And while the definition of "virginity" is fairly abstract, its consequences for young women are not. And that's why I wanted, and needed, to write this book. The Purity Myth is for women who are suffering every day because of the lie that virginity exists, and that it has some bearing on who we are and how good we are. Consider the implications virginity has on the high school girl who is cruelly labelled a slut after an innocuous makeout session; the woman from a background so religiously conservative that she opts to have her hymen surgically reattached rather than suffer the consequences of a non-bloody bedsheet on her wedding night; or the rape survivor who's dismissed or even faulted because she dared to have past consensual sexual encounters.

My reasons for wanting to write this book weren't entirely altruistic, however. I was once that teenage girl struggling with the meaning behind my sexuality and how my own virginity, or lack thereof, reflected whether or not I was a good person. I was the cruelly labelled slut, the burgeoning feminist who knew that something was wrong with a world that could peg me as a bad person for sleeping with a high school boyfriend while ignoring my good heart, sense of humour and intelligence. Didn't the intricacies of my character count for anything? The answer, unfortunately, was no, they didn't. It was a hard lesson to learn, and one that too many young women are dealing with nationwide.

Take the latest trend in virginity worship: purity balls. Fathers escort their daughters to these prom-like balls, where at some point the girls recite a pledge vowing to be chaste until marriage and name their fathers as the "keepers" of their virginity until a husband takes their place. Sounds a bit old school, but these events are becoming a nationwide phenomenon and received widespread media attention – from The New York Times to Dr. Phil – and parties are being planned in nearly every state in America.

From the book The Purity Myth by Jessica Valenti. Excerpted by arrangement with Seal Press, a member of the Perseus Books Group. Copyright (c) 2009.