Kathleen Stock is a Reader in Philosophy at the University of Sussex. She writes on the philosophy of fiction, and on issues in feminist philosophy. Her current research project focuses on conflicts of interests between trans women and natal women, and how to resolve them. Here, she examines arguments against expanding the concept of “trans women” to include anyone self-identifying as such.

What are concepts for? At least: for categorising things into useful groups. Concepts tell us what gets included and what doesn’t: for instance, books don’t normally get into the category of plates. This isn’t “exclusionary” in any sinister sense.

Some philosophers do “conceptual analysis”: roughly, tracking our current concept use and its implications. Let’s focus on the sentence “trans women are women”. It’s occasionally said that this is already widely accepted as an implication of the current public concept of “woman”. Certainly, some speakers sincerely believe it, but still, I think, the usage hasn’t spread widely enough for this to be persuasive. Most use trans people’s preferred pronouns and names, but arguably this only shows a wish, which I share, to be compassionate and respectful. It’s also true that British law recognises trans women as women, but again, this was not intended to settle conceptual disputes but to alleviate discrimination against trans people.

In the same vein, in recent philosophical discussion a different focus has emerged: “conceptual engineering”, or deliberate conceptual change, towards good social ends. In particular—sticking with our example—some philosophers say that, even if the current public concept “woman” doesn’t include trans women, we should actively engineer it to do so in future. It’s argued that this will vastly improve the experience of trans people, ultimately helping to minimise both their sense of gender dysphoria (distress caused by a mismatch between felt and perceived gender identity) and their susceptibility to transphobic violence. Trans activists emphatically agree. But crucially, they also effectively suggest that the concept “trans woman” should simultaneously be engineered. Namely, “trans woman” should include anyone who isn’t already a natal woman and who sincerely self-declares as a woman. Putting these two proposed acts of engineering together, we get: anyone who isn’t already a natal woman, and who sincerely self-declares as a woman, should be counted as a woman. In public discourse, there’s a lot of focus on whether trans women should be counted as women. Whatever the ultimate answer, that’s obviously a reasonable question, despite trans activists’ attempts to count it as “transphobic”. But I think we should also ask whether self-declaration alone could reasonably be the only criterion of being trans. There’s little precedent elsewhere. In a superficially comparable case, such as coming out as gay, there is still another underlying factor, sexual orientation, that secures your membership. It’s not just a matter of saying that you are gay. And though, as in the notorious case of Rachel Dolezal, a person might “self-declare” that she is “trans racial”, it has seemed clear to nearly everybody responding to this case that such a declaration would be not only false, but also offensive to genuinely oppressed members of the race in question. There is no such thing as being “trans racial”; there is only thinking falsely that you are. If it’s not self-declaration, but some other factor, that makes you trans, what’s that factor? Not all trans people seek surgery or take hormones; not all consistently dress or self-adorn in a stereotypical feminine or masculine way; not all have gender dysphoria; and neither trans women, as a group, nor trans men as a group, have any common sexual orientation. Equally, some people have gender dysphoria and yet resist calling themselves trans; some surgically add feminised features without being trans. And so on. All we seem left with is self-declaration.

If we agree, and also accept that trans women should be categorised as women, then ultimately this leaves us with: anyone who isn’t a natal woman, and who sincerely self-declares as a woman, should be counted as a woman. Both Theresa May, Britain’s prime minister, and Jeremy Corbyn, the leader of the opposition Labour party, have apparently enthusiastically taken up this conclusion. They want to change the law to allow gender self-identification via an administrative process of self-certification as the only criterion for legally changing the sex recorded on one’s birth certificate. However, I’ll now suggest that such a move is not cost-free. In particular, certain harms to original members of the category “woman” should be weighed against any gains.

One problem is that, since “woman” and “female” are interchangeable in many people’s minds, we’re likely to lose a secure understanding of the related concept “female”. (Indeed, some activists advocate stretching this concept to include trans women, too.) Yet the existing concept is in good order. It designates a person with XX chromosomes, and for whom ovaries, womb, vagina and so on are a statistical norm, even if some females are born without some of these, or lose one or more later. That intersex people exist doesn’t seriously threaten this category, since most categories have statistical outliers.

Nor does the existence of males born with none of these features, who then take hormones or undergo surgery to gain some such features artificially. Maintaining the concept “female” as it is is crucial to an understanding of a particular kind of lived physical experience, already significantly under-investigated in relation to other medical and academic specialties. To put it bluntly: if we were to lose this concept, and with it the concept “male”, we would have to reinvent them.

The category “female” is also important for understanding the particular challenges its members face, as such. These include a heightened vulnerability to rape, sexual assault, voyeurism and exhibitionism; to sexual harassment; to domestic violence; to certain cancers; to anorexia and self-harm; and so on. If self-declared trans women are included in statistics, understanding will be hampered. A male’s self-identification into the category of “female” or “women” doesn’t automatically bring on susceptibility to these harms; nor does a female’s self-identification out of those categories lessen it. In a sexist world which often disadvantages females, as such, we need good data. We need good data about trans people too, of course, but the two tasks should be separated.

Even more pressingly, if we lose a working concept of “female” in the way indicated, self-declared trans women (males) may well eventually gain unrestricted access to protected spaces originally introduced to shield females from sexual violence from males. We are already seeing the erosion of these, as companies and charities open formerly female-only spaces such as changing rooms, shared accommodation, swimming ponds, hospital wards, and prisons, to everyone out of a desire not to appear transphobic.

The problem here is male violence. The category of self-declared trans women includes many with post-pubescent male strength, no surgical alteration of genitalia, and a sexual orientation towards females. And, even currently, gender reassignment can legally change sex category on birth certificates. This leaves the future of “same-sex” spaces unclear. Note that this is emphatically not a worry that self-declared trans women are particularly dangerous or more prone to sexual violence. It’s rather that we have no evidence that self-declared trans women deviate from male statistical norms in relevant ways. There’s also a separate worry that violent males who do not consider themselves trans will eventually take advantage of increasing confusion about social norms about such spaces. Sex offenders already go to great lengths to access vulnerable females; there’s no reason to think they wouldn’t use this situation to their advantage. The construction of social spaces is necessarily coarse-grained. Once sex-based protections are gone, we can’t easily keep out only the dangerous people.

And changing the concept of “woman” to include self-declared trans women also threatens a secure understanding of the concept “lesbian”. Lesbians are traditionally understood as females with a sexual orientation towards other females. Again, the categorisation is socially useful. It helps members of the category understand themselves in a positive, distinctive way, despite living in a heteronormative society. It motivates them to create their own social spaces. It gives them special protections, as a discriminated-against minority; and access to special sources of charity funding. Some trans activists seek to engineer the concept “lesbian” too, arguing that, since self-declared trans women are women, or even female, self-declared trans women with a sexual orientation towards women, or females, are “lesbians”, and should have access to exactly the same social spaces, protections and funding. Furthermore, many self-declared trans women retain male genitalia. Some trans activists have it that female lesbians are “transphobic” for ruling out sexual attraction for those with male genitalia. The upshot of this is likely to involve confusion and shame for some emerging young lesbians, socially pressured into considering sleeping with males to whom they are fundamentally unattracted, as determined by their basic sexual orientation.

These are only some of the harms associated with introducing self-declaration as the defining criterion of being trans, whilst simultaneously counting trans women automatically as women. Harms also arise for females having to share already meagre sex-based resources with self-declared trans women (such as all-women shortlists for political candidacy, representation in the media and sports scholarships). They arise for post-operative “transsexuals” in relation to the approaching massive expansion of their defining category. And they arise for gender-nonconforming children, whose emerging world-view can be strongly influenced by trans-activist rhetoric about self-declaration. In sum, when deciding what the law should say, or even what our concepts should be, there are more things to consider than some trans activists would have you believe.

This is part of a two-week discussion on transgender issues, with ten contributors. The other contributions are available here.