A few months ago, I was invited to give a talk, this coming March, about my book Vagina: A New Biography at a new women-only club in London, named Grace Belgravia. I was happy to discuss the subject in a private all-female setting, in a discussion moderated by a figure in British feminism whom I have long admired, Rosie Boycott. It was intriguing, too, that the club seemed designed to be a challenge to, or at least a twist upon, the network of all-male spaces that have so long supported British (and American) power hegemonies.

But when the event changed to a more public one, my comfort level with an all-female invitation list changed as well. I asked the organizers to open the event to both genders, which, to their credit, they did. Viv Groskop, in the Independent, citing the women-only language on the invitation, wrote:

"Presumably if Mrs Carter wanted to attend, Mr Carter would have to stay at home. How is this any different to a golf club in the 1970s? … I can understand that people are tired of all the rhetoric and of waiting for things to change and so they're taking drastic action by reviving the sisterhood in both thought and deed. But there is a very fine line being crossed here … you end up creating a mirror image of the exclusive and excluding public spaces that feminism once fought against."

I agree with Groskop, in important ways – and, critically, when it comes to any public event or institution. Yet, I also see value for women, and men, too, even in a truly egalitarian world, in maintaining some kinds of same-sex spaces. The idea of a women-only club at all, or women-only schools and programs, at this stage of feminism, raises important questions about whether same-sex spaces in general have any value or validity any more. Is there, indeed, a line that separates valuable women-only spaces from those that are discriminatory or counterproductive?

In my mind, there is such a line.

Feminism in the 1970s was based on the truism that every woman needed "a room of one's own", a phrase that drew on Virginia Woolf's framing of the value of all-female colleges in the 1929 essay by that name. The phrase, in turn, became a cliché, spawning a thousand feminist books and college courses with "of their own" in the title.

And indeed, all-female gatherings did radicalize the generation western feminists of the 1970s, who were fighting a self-concept that had defined them always in relationship to men and male needs. Whether it was the "aha!" about invisible discrimination realized in a consciousness-raising group, the awareness of same-sex passion discovered in a lesbian retreat, or the context of a group of women learning about their sexuality from feminist sex educators such as Betty Dodson, the insights that emerged from these women-only gatherings would have been unreachable in mixed groups.

There are still breakthroughs in skills acquisition, learning and leadership that happen most easily in women-only settings. Grameen Bank has a record of great achievement with small business entrepreneurship by training low-income women in all female settings – so much so that it is a target for government seizure; as does the Barefoot College in Tilonia, India, founded by Bunker Roy in 1972, and the subject of a recent documentary by Jehane Noujaim, "Rafea: Solar Mama".This program turns desperately impoverished, illiterate women from Columbia, Kenya and Jordan into solar engineers within a six-month training period. The film shows how the sisterhood, support and freedom from male intervention and control liberate these women's capabilities and confidence.

Similar boosts to female leadership and self-esteem have long been documented in graduates of all-female US colleges such as Smith and Wellesley, and from the until recently single-sex St Hilda's and St Hugh's. And I have seen the vast leaps in confidence and skill set acquisition that comes from all-female training settings in the young women's leadership program I co-founded, the Woodhull Institute.

Counselors who work with male abusers know that an all-male setting allows for more personal responsibility to be taken on as men confront their peers. The Girl Guides' and Boy Guides' sex segregation allows both genders to focus on learning that supports their own development. For these reasons, I do see value in some single-sex programs and settings, even today.

But when there is now a trend of female-to-male transgender Smith undergraduates raising questions about "what is a Smithie?" – and even what is a woman, or a man – how do we justify women-only events, training or ideologies? How do we justify them when the best and most appealing version of feminism on college campuses is one in which young men feel included in exploring gender issues, and have a place in championing fairness to women?

And how do they make sense after what I saw when we sent young female alumni from Woodhull with new financial skills back to their low-income neighborhoods, and their boyfriends clamored, rightly, for a program of their own? Even on college campuses, young women and young men reasonably ask whether there should even be a "women's center" at all.

My best sense is that all public institutions, events and gatherings should be open to all without discrimination. But is there is still a place for the occasional same-sex discussion group, training program and private gathering? I believe there is. In my ideal world, so long as we have a larger goal that what is learned separately is always directed back to a discussion that brings us all together.