When Simone de Beauvoir declared in 1949 that “one is not born, but rather becomes a woman,” she upended the broadly held notion that sex is a simple, biological given. She challenged the long-held belief that our sex alone determines our destiny, showing instead that social forces—and our own choices—shape who we are.
More than 75 years later, her insight still holds true: we continue to “become” women. Yet today, society not only limits what a woman can be, but also controls who may even enter that category.
Who truly belongs to a sex? Who is really a woman? And how many sexes are there, anyway? These questions have become a political battleground in a culture war.
A war that, on the surface, Trump has declared done. One of his first executive orders firmly set the tone for his administration’s position on how many sexes there are: “‘Sex’ shall refer to an individual’s immutable biological classification as either male or female.”
Trump was clear: sex is binary. No discussion, no further questions. Neither in political nor in scientific discourse.
And on 16 April 2025, another court decision poured fuel on the fire. The UK Supreme Court announced its ruling in the case Women Scotland Ltd (Appellant) v The Scottish Ministers (Respondent): “[…] the term ‘woman’ […] is limited to biological women and does not include trans women.” The consequence of this decision is that trans women are to be excluded from any women’s quotas; that is, the court decided who is considered a ‘woman’ under the Equality Act 2010 — and who is not.
But of course, the court’s ruling is more than just a decision in this specific case; its impact extends far beyond women’s quotas, as it responds to the broader question underlying the case: who really is a woman? In the UK, from now on, individuals whose legal gender is female may not be recognised as women.
The decision sparked widespread protests. Thousands of people across the country — from London and Oxford to Manchester — took to the streets to support trans rights. The protesters chanted “trans rights, human rights” and emphasised that the government needed to “put the equalities law back on sound footing”.
Furthermore, in response to Harry Potter author J.K. Rowling’s stance backing the Women Scotland Ltd’s case, many members of the Harry Potter cast signed an open letter calling for action on trans rights in the film industry. They made it clear that they did not side with Rowling on the matter—and do not share her understanding of feminism.
What does this tell us about our present? After years of strengthening queer rights and widespread debate over how independent biology is from the cultural perception of binarity, we now see governments all over the world taking several steps back. To put it differently: why does selling (binary) sex work so well?
Gender and sex have long been popular topics of discourse— largely because we all ‘have’ them. As we move through the world, we may not be able to confidently determine the exact impact of CO₂ levels on the environment at any given moment; yet many people trust that climate scientists’ concerns are well-founded.
But when it comes to gender and sex, we walk through the world feeling both able and compelled to categorise everyone, including ourselves.
Trans people have challenged fixed categories since ancient times. With the trans and non-binary rights movements, they not only gained visibility in public discourse but also claimed their own labels—and could no longer be ignored.
When long-held certainties over gender and sex are questioned, the confidence in being able to categorise others and ourselves is unsettled.
It’s not only trans and non-binary people—by their very existence—who challenge our long-held categories, but science itself. The science we so often regard as the source of ‘facts’ and ‘truths’ doesn’t fare any better, as a quick look at the search-engine results shows: articles titled “Why There Are Only Two Sexes” appear alongside pieces proclaiming “Nature and sex redefined – we have never been binary.”
Sex is no longer—and never was—just a scientific matter; it has always been a political battleground. From its ties to the fight for women’s and queer rights to its place in gender, women’s, and queer studies since the 1960s, it’s far more than biology. It’s a symbol of how reality can diverge from what we’ve been told.
When Trump moves to politically define how many sexes there are, he’s doing more than declaring a version of the truth—and ignoring the contradiction in claiming to ‘decide’ what truth is. He becomes the living example of Michel Foucault’s notion that power in discourse determines what becomes ‘true.’
He’s offering an identity marker for those who cling to the belief in two sexes (and two genders, for that matter). It’s a signal: You belong with us—the ‘rational’ people who believe in ‘nature,’ ‘reality,’ and so on. It’s another sign of the close ties between the MAGA movement and religious fundamentalists in the U.S.
In the UK, something different happened. The Supreme Court has a judicial, not an executive, function, which should imply no political or strategic intent. However, its decision carries political consequences and, regardless of its role, becomes part of the battleground of identity politics.
Their reasoning is not as polemical or authoritarian as Trump’s, but it still feeds into a narrative he likely approves of: the desire for certainty, for a simpler reality. As the justices wrote in their decision: “A biological definition of sex would make it simpler to make a women’s-only ward a space for biological women.”
But it’s questionable whether this really makes things simpler—or safer. Women who want to exclude trans women from their spaces argue that these spaces are no longer safe, while overlooking—or deliberately accepting—that trans women will instead be forced into spaces with cis men, where they face real risks.
The ruling was welcomed by political leaders. PM Keir Starmer, once a vocal supporter of trans rights, endorsed the decision: “It’s a welcome step forward. It’s real clarity in an area where we did need clarity.”
But the question remains: clarity for whom? This ‘clarity’ is a slap in the face to more than 200,000 non-binary and trans people in England and Wales—and to everyone who considers themselves an ally of these communities.
Politics sells sex: for clarity, for simplicity, for a battleground where one side fights for—and claims to win—the ‘truth.’ Where identities are negotiated—often over the heads of the very people whose identities are at stake.
If the time and energy spent debating how many sexes there are, and who truly belongs to a sex, were instead directed toward making the world safer for all women—cis and trans—and toward fighting gender-based violence and inequality, we could all benefit. But that, of course, is far more complicated.
Acknowledging that who we become is shaped far more by external forces than by innate traits—as de Beauvoir made clear in 1949—is a painful realisation. It forces us to wonder who we might be without society and whether we can ever truly be ourselves.
Yet this insight can also empower us to challenge societal authority—a power that today reaches further than ever, not only in dictating which women we should become but also in deciding who may become a woman.