Time-travel with me to the late 1970s, inside the headquarters of the Berkeley Women’s Health Collective. Its storefront windows are draped in Indian-print bedspreads, shielding the free-pelvic-exam patients and women’s consciousness-raising groups from curious passersby. The bricks-and-board shelves are loaded with books, many of them missiles fired by one side of the feminist “sex war” at the other. All across the country, in “wimmin’s” groups like BWHC; at conferences and in books and position papers, two factions have been arguing a pivotal issue facing the second-wave women’s movement: How should feminists have sex?

First-wave feminists focused on the burning issue of their day — suffrage. The second wave is focused on cultural critique. Our motto is “the personal is political,” and what could be more personal, or more provocative, than sex?

One problem: We can’t agree on what, exactly, feminist sex is. After Betty Friedan dubs lesbians the “Lavender Menace,” big internecine questions only get bigger: Are lesbians a threat to feminist goals, or its purest proponents? Is hetero sex inherently oppressive to women? Is consensual sexual power-play empowering, or a perpetrator of patriarchy? Should pornography be banned for promoting violence against women, or defended as free speech?

Books from both sides are proliferating, deepening divisions in our already fragmented movement. In the “anti-sex” camp, Susan Brownmiller argues that men use rape to perpetuate male dominance by keeping all women in fear; Catharine MacKinnon opposes porn, which she says, is a form of human trafficking; Andrea Dworkin defines all sex involving force as rape. From the “sex positive” faction, we have “Our Bodies, Ourselves” and Germaine Greer’s “The Female Eunuch.” Gayle Rubin and Pat Califia write articles calling all consensual acts, including sadomasochism, a form of women’s emancipation. Ellen Willis accuses the anti-porn camp of puritanism and disparaging free speech.

Back in Berkeley, the same battle has been brewing. Today it comes to a vote. Sitting in a non-hierarchical circle, braless in our “Women’s Struggle Is Class Struggle” T-shirts, the BWHC Steering Committee — all of us in our 20s and early 30s, all White and middle-class — discuss the motion on the floor. Should we purge the BWHC of internalized sexism — and thereby, since most of us have boyfriends, sex — by voting ourselves gay?

The yes vote is called. Six women raise their hands, flashing thick thatches of unshorn underarm hair. Two, including me, vote no. I’ve actually had some same-sex stirrings, but I’m madly in love with my boyfriend, who keeps warning me, “if you hang out with those lesbos, they’re gonna turn you into one.”

Zoom forward to 2021. My boyfriend’s nightmare came true: At age 69, I’ve been a lesbian half my life. I’m also a book critic, and I’ve spotted a trend in the galleys that land on my porch. Just as books launched the second-wave sex war, today many feminists in their 30s and 40s are riding a fierce, no-holds-barred feminist wave, writing fierce, no-holds-barred books about sex.

Their sex.

In many cases, their kinky sex.

About which they seem to feel no shame.

Feminists having sex? Kinky sex? In print? Without shame? Now there’s a gift that second-wave feminism failed to give. How many potential feminists, I wonder, were turned away from the women’s movement of my day because they felt forced, as I did, to choose between their bodies and their beliefs; their personal proclivities and their politics?

Accepting no such binary bifurcation, these passionate, polemical sexual confessionals make me exhale a breath I’ve been holding for 50 years. At long last, the women’s liberation movement is advocating for the actual liberation of women! Unlike 1970s consciousness-raising groups, in which mostly straight, mostly White women whispered our secrets to each other in cloistered kaffeeklatsches, these third-wave women — heterosexual and queer, coupled and thrupled and single, vanilla and kinky, Black and Brown and Asian and Native American and White — are publishing their complex, controversial sexual truths for all the world to read.

In the past year alone, sex journalist Tracy Clark-Flory released “Want Me,” busting herself for a decade of orgasm-faking hookups, followed by conversion to the “traditional romantic fairy tale,” complete with diamond engagement ring. In “Girlhood,” Melissa Febos proves that it’s never too soon or too late for a female to claim her own sexual agency. Self-identified adulteress and breast cancer survivor Gina Frangello writes in her memoir “Blow Your House Down” of wanting more from her life, and from her soon-to-be ex-husband, who sometimes engaged her kinks to appease her, but left her feeling humored and lonely. And “Kink,” an anthology edited by R.O. Kwon and Garth Greenwell, includes a steamy fictional chapter by Roxane Gay in which a married woman ruminates about her willing wife who “wants me to take her somewhere — a place she has no vocabulary for — a place neither of us has been. . . . I can hear it in her cries when we’re crammed into the antiseptic space of the train bathroom.”

In interviews with these and other super-sex-positive authors, they tell me of feeling oppressed (as well as grateful for the inroads carved) by second-wave feminism.

“Some anti-sex feminism, like Dworkin’s, did not resonate with the masses,” Frangello says, triggering flashbacks to the alienation I felt, being asked to vote myself gay.

Carmen Maria Machado, whose stunning 2017 memoir, “In the Dream House,” details her abusive relationship with a former female partner in kink, struggled with that alienation, too. The legacy of her feminist forebears (regretfully including me: guilty by association if not by intention) made her fantasies feel problematic.

“For decades, feminists conflated wanting to be hit and internalized misogyny; wanting to hit and being a domestic abuser,” Machado says. “I struggled with why I wanted things sexually that I didn’t want in real life. I had to decide if I was going to live the lie of acceptability, or if I was going to live. A whole lot of people walked before me, so I could run. I ran.”

Febos, likewise, “came of age reading second-wave texts like ‘The Feminine Mystique’ and ‘The Beauty Myth,’ and the work of Andrea Dworkin. My feminism was profoundly informed by them, but some of their views seemed narrow to me, especially as a queer woman. And I was frustrated that many second-wave feminists didn’t seem to believe that you can be a feminist and also have fantasies and desires ranging from hetero sex to sadomasochism and beyond.”

Cultural lightning rod Katie Roiphe, who takes a rare turn to memoir in 2020’s “The Power Notebooks,” agrees. “There was a feminist fantasy that you could somehow disentangle sex from aggression. I think that’s wrong. Power is inexorably bound up with sex. It’s part of the good experience. The idea that one should resolve one’s rape fantasies through feminism is a leftover problem from the ’70s.”

Gay, whose first fictional erotic story was published in 2001, has argued publicly with many of Roiphe’s views, but on this issue the two agree. “Having fantasies of submission is just a fantasy,” Gay says. “When you act on it, it’s just sex. Kink is actually incredibly feminist, because it requires a framework of consent. There’s nothing more feminist than that. It’s radical and it’s powerful to talk openly about desire.”

These young carriers of the flame are capturing today’s post-#MeToo moment, writing radically, powerfully and beautifully about a fuller freedom than their foremothers dared imagine when a women’s right to vote, to carry her own credit card, to decline sex with her husband seemed beyond reach. In 2021, the dream of gender equality is far from fulfilled. But especially when compared with the gains and losses of other civil rights movements, as George Floyd’s public murder made clear, the progress made in my lifetime by the women’s liberation movement is breathtaking. These new feminist books reflect that progress and advance it.

“I believe sex-positive feminism is inclusive feminism, and I believe in the power of literature to change thinking and lives,” Frangello tells me. “When I read Carmen Machado, it was like gulping air: ‘Yes please, talk about your body, I have a body, too.’ ”

“For me, it was way more embarrassing to admit that a woman had me groveling for a really long time than it was to name the kind of sex we had,” Machado says. “Writing about bodies, and about kink, liberates women from the idea that your sexual practices make you ‘other.’ We need to stop believing that one sexual practice is the organic norm. I hope for a future in which we no longer have reasons to label certain sexual behaviors as kinky at all.”

Gay, too, is bullish on feminism and sexual liberation; bearish on shame.

“Our social mores around sex are shifting,” she says. “We’re in a moment of sex positivity, which I think is extremely healthy. Women have more of a voice — not enough, but we’re heading in the right direction. We’re allowed to be empowered, to act on our desires without shame. We’re having more enriching conversations about the types of sex we have and who we have it with.”

Writing sex, even fictionally, makes Gay feel vulnerable, she says. But she’ll continue to do it regardless. “Other people’s judgments are not my problem,” Gay concludes. “The shame is theirs, not mine.”

Meredith Maran is a journalist, critic and the author of “The New Old Me: My Late-Life Reinvention,” among other books.