ame a female thinker with an eponymous adjective. The man-derived words are commonplace: Aristotelian, Confucian, Trotskyist, Churchillian. Two queens, Elizabeth I and Victoria, have great chunks of British history and culture named after them. But this is not the same thing. In fact, with the exception of Thatcherism, it’s hard to find a noun describing a woman’s ideas that is in anything approaching general usage in the UK. Even the novelists Jane Austen and George Eliot don’t have a style named after them in the way that Charles Dickens (Dickensian) and Henry James (Jamesian) do. It’s obviously no great puzzle to work out why this is. Intellectual life has mainly been stewarded by men. That’s one reason why Virginia Woolf is such a pivotal figure – and why Woolfian is one more exception to the rule above. She thought about ideas, and where they come from, all the time. “We think back through our mothers if we are women,” she wrote in her seminal essay about female exclusion, A Room of One’s Own. Why am I writing this now? Because recent events have forced me, like many others, to think much harder than I have been used to about feminism. The immediate cause is a conflict of opinion about transgender activism and the reasons behind an increase in the number of girls referred for treatment for gender dysphoria in England, from 32 in 2009/10 to 1,740 in 2018/19. But debate on these issues has exposed a faultline with wider implications. These arguments featured at the start of this year, after some candidates for the Labour leadership signed a “trans pledge” that labelled the feminist campaign group Woman’s Place UK a “hate group”. During the early months of the pandemic, hostilities were partly suspended. But they exploded again in the buildup to last week’s announcement by the UK government that it has decided against changing the law to allow people to change their legal sex without a medical diagnosis, although the process will be made easier and cheaper. With the topic routinely described as “toxic”, it’s unsurprising that many people’s reaction is to avoid it. But I think this avoidance also reveals a lack of interest in feminist political philosophy – and the rift that has opened up between adherents of two key thinkers. Simone de Beauvoir’s 1949 book The Second Sex set the stage for feminists in postwar Europe. She was determined to unpick the masculine/feminine hierarchy that made women subordinate. But she believed biological differences as well as social forces were important. “The body being the instrument of our grasp upon the world, the world is bound to seem a very different thing when apprehended in one manner or another,” she wrote. Later authors developed these ideas, introducing the term “gender” and taking feminist approaches into fields including history, law and literary studies, as well as activism. Scholars, including Avtar Brah in the UK and Kimberlé Crenshaw in the US, offered crucial insights into the ways that white feminism erases the experiences of black and minority-ethnic women. But the idea that a woman is made (“not born”) out of a female body was mostly accepted until the early 1990s, when the US philosopher Judith Butler sought to overturn it. Butler’s argument, set out in her books Gender Trouble and Bodies That Matter, is that sex is “no longer a bodily given” but a discursive concept: “a process of materialisation that stabilises over time”. Rather than treating their sexed bodies as the underpinning of their politics, she argued, feminists should embrace the fluidity of gender. Liberation from the patriarchy would be won alongside gay, lesbian, transgender and queer rebels against heterosexism. Feminists do not need to have read Butler or Beauvoir to be influenced by them; many Marxists, after all, have not read Marx. And of course, the trans experience did not begin with Butler. Any discussion of trans identities and politics must start with trans authors. But if the impasse between Beauvoirian, gender-critical feminists on the one hand, and Butlerian and queer feminists on the other, is ever to be overcome, it is essential to acknowledge the philosophical basis as well as the practical implications of their disagreement. In particular, it should be recognised that, as the scope of the terms “trans” and “transgender” have expanded to include a range of identities, no longer referring only to people who have undergone a medical or surgical transition, the relationship between trans activism and feminism has also shifted. That’s because of the importance placed by gender-critical feminists, including me, on the body. Of course we don’t agree on everything, any more than LGBTQ activists do. But broadly speaking, our analysis is that women’s lives are shaped by their physical differences from males as well as the cultural meanings derived from these. The exploitation of women’s domestic and caring labour, for example, is linked to (though not justified by) our role in reproduction. Female anatomy makes us vulnerable in specific ways to sexual violence, such as pregnancy from rape. Our breasts are the most common site of cancers among women. Understanding sexual difference to be an important facet of human experience, we seek a form of equality that recognises it. We do not accept the much newer concept of gender identity (the feeling of being male or female) as a substitute. And we think the idea that “sex” can be discarded in favour of more inclusive terminology, as advocated by Butlerian feminists, is naive. Because if “sex” ceases to be talked and thought about, how will we recognise and tackle sex-based oppression, not just in western countries but around the world? There are those who will say: I can fight for sex-based rights and accept the concept of gender identity – that subscribing to Butlerian theory doesn’t mean you can’t defend abortion rights. In the short run, it doesn’t, of course. The problem is that this kind of political practice is grounded in theory and, as much as some might like it to, can’t float free of it. Over time, the internal contradictions created by definitions that are subjective and unstable will, I think, pull gender-based feminism apart. By adhering to what I have called a Beauvoirian feminism, I don’t aim to invalidate anyone else. I recognise the importance of the concept of gender identity for trans people. But it (and with it, the term cisgender) can’t be forced on to women like me who regard questioning gender roles, while advocating on behalf of our sex, as the whole point of feminism. Nor is it accurate to describe us as “trans-exclusionary radical feminists”, as Butler did last week. Gender-critical feminism is more varied than that. (My own influences, for example, include Kleinian psychoanalysis and evolutionary biology.) None of this means “GC” feminists are in favour of bigotry, or don’t care about the obstacles and prejudices faced by transgender people, or that we deny the existence of people with differences in sex development. What it does mean is that we think rejecting sex as a way of thinking about ourselves would be a terrible error. And that we urgently want to be able to discuss this, in a respectful way, with those who disagree. Across the world, women’s rights as well as LGBTQ people’s are under threat (in the UK, according to one recent survey, more than half of men aged between 18 and 24 think feminism has “gone too far”). If feminists are to push back, clear analysis of the problems facing us is just the first step. • Susanna Rustin is a Guardian journalist