Why the question of categories matters

"What is a woman?" sounds like a question for a dictionary. In the debate over gender identity it has become one of the most fought-over questions in public life. It matters in law, medicine and sport, and in the private reasoning of anyone who has wondered whether they are "really" the opposite sex. Behind it sits one of philosophy's oldest problems: what makes a category real? Is a kind defined by a hidden inner nature, by observable features, by social arrangements, or by what members say about themselves?

This page traces that problem from Plato to current philosophy of gender. It then looks at how detransitioners use these ideas, often without the technical vocabulary, to make sense of their own realisation. It belongs to a series on the philosophical frameworks people use to understand gender distress and its resolution.

Two terms run through everything below:

• Essentialism: the view that members of a kind share an essence, a set of properties that makes them what they are and explains their other features.
• Nominalism (from Latin nomen, "name"): the view that only individual things exist, and that general categories are names or concepts we use to group them, not extra entities in the world.

Most positions lie between these poles, and "essentialist" has also become an accusation that both sides of the gender debate throw at each other.

Plato: Forms and the joints of nature

Plato (c. 428–348 BCE) held that the things we perceive are imperfect, changing copies of Forms: perfect, unchanging, mind-independent patterns such as Beauty, Justice or Equality. A particular beautiful thing is beautiful because it "participates" in the Form of Beauty. On this view universal categories are more real than the individuals that instantiate them.

Plato also gave philosophy its best-known image for good classification. In the Phaedrus, Socrates recommends:

dividing things again by classes, where the natural joints are, and not trying to break any part, after the manner of a bad carver. — Plato, Phaedrus 265e (Perseus translation)

"Carving nature at its joints" is still the standard image for classifications that track real divisions rather than arbitrary ones (Franklin-Hall, "Plato's joints"). The sex/gender debate is, in part, an argument over where the joints are.

Aristotle: essence, definition and kinds

Aristotle (384–322 BCE) rejected separately existing Forms. For him the form or essence of a thing exists in the thing. A thing's essence, which he called to ti ên einai ("what it is to be"), is captured by a definition naming its genus and its distinguishing feature. A human, in his famous example, is a rational animal. Accidental properties, such as being pale or tall, can change without the thing ceasing to be what it is (SEP: Aristotle's Metaphysics).

Aristotle also wrote at length about male and female. In Generation of Animals he defined them by their reproductive role: the male generates in another, the female generates in itself. He then loaded that definition with a hierarchy, describing the female as a kind of incomplete male, which later feminists rightly attacked. Both moves are ancient: defining the sexes by reproductive function, and attaching claims about women's inferiority and proper roles. Much of the modern charge of "biological essentialism" targets the second move, not the first.

The medieval problem of universals

Medieval philosophy inherited the question in a compact form. The Neoplatonist Porphyry had raised, and then set aside, three questions about genera and species: whether they are real or exist only in thought, whether they are bodily or not, and whether they exist apart from things or in them (Klima, SEP: The Medieval Problem of Universals).

• Realism: universals such as "humanity" are real. Augustine placed Plato's Forms in the mind of God as divine ideas.
• Moderate realism (Avicenna, Thomas Aquinas): a common nature really exists, but only as individualised in particular things and as abstracted by the mind. The same human nature is in Socrates and in Plato, but not as a separate object.
• Nominalism (William of Ockham, c. 1287–1347): only individual things exist outside the mind. Universals are concepts, natural signs in the mind that stand for many individuals. Ockham's principle of parsimony, later called Ockham's razor, says not to multiply entities beyond necessity.

These labels are useful. Many detransitioners quoted below are realists about sex and nominalists about gender: sex is a real division in nature, while "gender" names social patterns with nothing behind them. Popular gender identity theory often reverses this, treating an inner gender as the real thing and the body as secondary.

Locke: real and nominal essence

John Locke's Essay Concerning Human Understanding (1690) introduced a distinction that fits the gender debate closely. A thing's real essence is, in Locke's words, the "real internal, but generally in substances, unknown constitution of things, whereon their discoverable qualities depend" (Essay III.iii.15, quoted in the Routledge Encyclopedia of Philosophy). Its nominal essence is the abstract idea we attach to a name: the bundle of observable qualities we use to sort things into kinds (SEP: Locke's Philosophy of Science).

Locke doubted we could know real essences, so he thought our sorting was largely conventional. Applied to gender, his distinction separates three things often run together:

1. The observable cluster we use to sort people in daily life: face, voice, build, clothes, mannerisms. This works like a nominal essence. It is usually reliable and sometimes wrong.
2. The underlying basis on the biological view: the body's developmental organisation around one of two reproductive roles. Unlike Locke's hidden corpuscles, modern biology can examine this directly.
3. A posited inner gendered self on the gender identity view: something invisible that is supposed to make a person a man or woman whatever their body. This is the claim that critics compare to a soul, a "real essence" that no observation can reach.

Much confusion comes from treating (1) as evidence for (3): someone who doesn't match the stereotyped cluster for their sex concludes that their hidden "real" self belongs to the other sex. The gender stereotypes page explores that error.

Modern natural kinds: Kripke, Putnam and Boyd

In the 1970s Saul Kripke and Hilary Putnam revived essentialism about natural kinds. In Naming and Necessity (Kripke 1980) and "The Meaning of 'Meaning'" (Putnam 1975), they argued that kind terms like "water" or "gold" refer to whatever shares the underlying nature of the samples we first used the word for. They do not refer to whatever matches our description. Putnam's Twin Earth thought experiment imagines a liquid identical to water in every surface respect but made of a different chemical, "XYZ". It would not be water, because water is H₂O (SEP: Natural Kinds).

Philosophers of biology objected that living kinds don't work like elements: species vary and are defined by lineage and interbreeding, not a shared intrinsic essence. Richard Boyd proposed homeostatic property cluster (HPC) kinds (Boyd 1999). Their members share a cluster of properties held together by underlying mechanisms. No single property need be universal and the edges can blur, yet the kind is real and supports reliable predictions.

Sex fits this model well. Biologists define the sexes by the two gamete types of anisogamous species (species with two very different sizes of reproductive cell): small sperm and large ova. There is no third gamete type (Lehtonen & Parker 2014; Goymann et al. 2023). Around that anchor sits a cluster of traits: chromosomes, gonads, hormones, genitals and secondary sex characteristics. Developmental mechanisms usually keep the cluster together. Differences of sex development (DSDs) are conditions in which one step of that development is altered. They create unusual combinations, not a third category or a spectrum. Each still develops along one of two pathways, as the intersex and DSDs page explains.

So the modern biological definition isn't essentialist in the old sense. It doesn't claim every female shares a fixed list of properties, let alone a personality. It says that a body organised or developing towards one reproductive role belongs to one of two classes, even when infertile, before puberty, or after surgery.

Social kinds and social construction

Not every real category is natural. Money and marriage are social kinds: they exist because of human practices, and are no less real for that. To call something socially constructed is to say it exists, or has its features, because of social arrangements.

Haslanger: "woman" as a social position

The most influential social-constructionist analysis of gender is Sally Haslanger's (Haslanger 2000; Haslanger 2012). Her project is ameliorative: she asks not only what we mean by "woman" but what concept would best serve the goal of understanding and ending sex-based injustice. Her definition:

S is a woman iff [by definition] S is systematically subordinated along some dimension (economic, political, legal, social, etc.), and S is 'marked' as a target for this treatment by observed or imagined bodily features presumed to be evidence of a female's biological role in reproduction. — Haslanger, as quoted in (Mikkola, SEP: Feminist Perspectives on Sex and Gender)

Two features are often missed. The account is anchored to the female reproductive role: being a woman means being treated in a subordinating way because one is seen as female, not self-identifying. And it is avowedly political: its aim is a world without women in this sense, where sex no longer marks anyone for subordination. Critics note it implies an unsubordinated female, such as a powerful queen, would not count as a woman. Katharine Jenkins later argued that Haslanger's method should yield a second concept, gender as lived identity, which would include trans women (Jenkins 2016).

Other social accounts include Natalie Stoljar's resemblance nominalism, on which "woman" is a cluster concept (people count by resembling paradigm cases across sex, bodily experience, social role and self-attribution), and Ásta's conferralism, on which sex and gender are statuses conferred by others and institutions (Mikkola, SEP; Ásta 2018).

Hacking: kinds that change the people classified

Ian Hacking added a crucial point: unlike electrons, people know how they are classified. They may embrace a label, reshape memories and behaviour around it, or resist it, and that in turn changes the category. Hacking called these interactive kinds and the process the looping effect (Hacking 1995; Hacking 2006). His examples included multiple personality disorder.

Looping helps explain modern gender identities. A newly available category ("trans", "non-binary", "egg") offers a story that can reorganise a person's past, as the gender as explanatory framework page discusses. The category is real as a social fact and a lived identity; that doesn't make the inner essence it describes real.

Psychological essentialism

Susan Gelman's research found that children spontaneously assume categories like "dog" or "boy" have a hidden inner nature explaining their visible features. She described essentialism as "an early cognitive bias" (Gelman 2003). This may help explain why "I was always really a girl inside" can feel compelling: it fits a deep habit of looking for an invisible essence behind appearances.

Applying the frameworks: what is a woman?

Three broad answers dominate academic and public debate.

The biological answer

Alex Byrne argues, from dictionaries, ordinary usage and the parallel with "girl", that "woman" simply means adult human female, as "mare" means adult female horse (Byrne 2020). Kathleen Stock's Material Girls (Stock 2021) argues more broadly that sex is binary and matters materially for medicine, data, sport, single-sex spaces and feminist politics; that borderline cases such as DSDs don't undermine it any more than they do other biological categories; and that "gender identity" is too poorly defined to replace sex in law and policy. Stock, a philosopher of fiction, suggests some trans people's self-understanding can be seen as immersion in a fiction, which she presents as compatible with respect for trans people and many of their rights.

In its strongest, Putnam-style form: "woman" picks out a real kind, and stereotypes are only surface features used to recognise its members. A masculine woman is still a woman, as an unusual sample of gold is still gold.

The social-position answer

Haslanger agrees with the biological view that the category is anchored to perceived female reproductive features, but holds that what matters is the social treatment built on that perception. Gender-critical critics object that this makes womanhood depend on oppression; trans-inclusive critics, that it excludes trans women not perceived as female.

The self-identification answer

Talia Mae Bettcher criticises both the "wrong body" model and the "beyond the binary" model of trans identity. She distinguishes a weak wrong-body view (one becomes a woman through surgery) from a strong one (one's real sex is set by an innate gender identity) (Bettcher 2014). Her own account rests on what she calls the multiple meanings of gender terms:

In analyzing the meaning of terms such as 'woman,' it is inappropriate to dismiss alternative ways in which those terms are actually used in trans subcultures; such usage needs to be taken into consideration as part of the analysis. — Bettcher (2013), as quoted in (Mikkola, SEP)

She also defends ethical first-person authority: an avowal of one's gender is an act one takes responsibility for, not a report open to correction by others (NDPR review of "You've Changed"). Robin Dembroff goes further. They reject what they call the "Real Gender assumption", the idea that classification should follow facts about who "really" belongs to a gender kind. They argue that dominant gender kinds unjustly constrain trans and non-binary people, so membership facts should not settle how people are classified (Dembroff 2018). Dembroff has also argued that Byrne wrongly assumes a single fixed meaning for "woman" (Dembroff 2021; reply: Byrne 2021).

These are serious positions that avoid the crude "inner soul" version of gender identity. Critics raise three objections. "One who identifies as a woman" is circular unless the identification's content is spelled out, and when it is, it tends to fall back on sex or stereotypes. Moving from metaphysics to ethics changes the question: it explains why one might call someone a woman, not what a woman is. And the law has to draw lines somewhere, which is why these debates resurface in sex-versus-gender legislation.

The "gender essentialism" charge, in both directions

Both sides of the debate accuse the other of essentialism, and each charge has some force against some versions of the other view.

The charge against gender identity theory. In popular and clinical forms, gender identity theory often posits an innate inner gender that can contradict the body, and reads gender non-conformity as its sign: the tomboy who is "really" a boy. Critics argue this revives the old sexist idea of male and female natures of mind, merely relocating the essence from body to brain or soul. Some detransitioners describe their own former thinking this way, as quoted below.

The charge against the biological view. Many trans commenters and some queer theorists argue that defining women by reproductive biology is "bioessentialism", reducing women to their bodies and echoing Aristotle and Freud's "anatomy is destiny". Defenders reply that a thin biological definition ("women are adult human females; the rest is personality") is not determinism about roles or minds ("females are naturally nurturing", or "a feminine boy has a female brain"). The definition says nothing about what a woman must like, wear, feel or do. Determinism, in its traditional or its gender-identity form, does. The charge is still fair against arguments that slide from sex to character, a slide some gender-critical commenters themselves warn against.

The mind–body dualism page takes up the related question of whether a gendered self can come apart from a sexed body at all.

How detransitioners use these ideas

On r/detrans, threads asking "what is a woman?" draw a consistent answer: adult human female. More interesting than the slogan is what commenters do with it. Many use the thin biological definition specifically to release themselves from stereotypes:

Just because a group is defined by a characteristic doesn't mean that characteristic defines all individuals. I am a musician because I play an instrument. That doesn't mean that all musicians play the same instrument… —AlpacaAlias, desisted female

I wish I'd realized that gender is fake. Seriously. Being female was literally the only requirement I needed to be a woman. I didn't need to feel or think or wear or do anything to be a woman. I just.... Was. —VeraDicere

Some describe the definition itself as easing their distress:

Just being a female human who's an adult. I found that once I realized that's literally the only thing that makes me a woman, I lost a lot of the gender dysphoria I had. —Fujohime, desisted

Nominalism about gender

Many commenters take the medieval nominalist line on gender: a name for social patterns, not a property inside a person. One detransitioned woman made Hacking's point that such a property depends on others to sustain it:

If you are alone, 'gender' of this sense immediately evaporates. It is a social game people choose to play with one another. It doesn't exist without others to maintain it. Therefore it is not an intrinsic trait someone can possess. —Soggy_Agency_7062, detrans female

A recurring theme is that gender identity theory holds two incompatible views at once: gender is a mere social construct, and an innate essence worth changing the body for.

On the one hand, the idea that gender is a social construct supports the belief that your perceived birth gender is not significant and therefore can be altered at will, and on other hand, the claim that you have an essential gender identity and it's important for you to transition to your "real" gender assumes that gender is an innately true element of the self. —bigbeard61, desisted male

Essentialism turned around

Some comments turn the "essentialism" charge around, describing their former reasoning as a hidden essentialism that tied body parts to social meaning:

It's gender essentialism in my opinion, just a non-traditional kind. Tying social roles to sex characteristics yet again, but this time encouraging people to change their bodies to "match" their desired expression, rather than changing their expression to "match" their bodies. —Quiet-County-9236, detrans female

One side of the argument says "if you are a female, you must do x, y, and z," while the other says, "if you do x, y, and z, you are a female". Both are reductive and toxic mindsets. —datinsatan, desisted female

One commenter made an analogy that captures the nominalist stance exactly:

I'm 'agender' to gender, the way I'm atheist to theism. I don't consider this a trans identity. —eyesclouds, desisted male

The comparison of gender identity to a soul is common in these accounts. The religion and spirituality and mind–body dualism pages explore it further.

Detransitioners don't speak with one voice. One woman sympathetic to radical feminism rejected an online "bioessentialism" casting males as biologically bad and females as good, preferring an explanation based on socialisation. Another recalled the hostility she met for saying, after stopping testosterone, that her biology mattered to who she is:

They accused me of being a bigot and a "biological essentialist" like it was a dirty word. —sewreadknit, desisted female

From definition to realisation

For some, the shift from an identity-based to a sex-based category was the turning point itself. One detransitioned woman described asking her doctor what she needed to do to "count" as a woman again:

…she said, nothing. I didn't have to do anything; I was a woman. That statement really tells you everything, even though from her perspective, she was affirming an identity. From my perspective, even though I'd had all these changes to my body, what determined my sex still remained. —NefariousnessLate375, detrans female

This sort of realisation is not always comfortable. One desisted woman put it plainly: "Sometimes that biological reality hurts. That's life." (Star_Aries, desisted female). In the detrans.ai analysis of about 3,094 r/detrans users who described transitioning in some form, "came to accept their biological sex" was the main reason for detransition in roughly 12% of accounts. "Came to see the social construction of gender as the real problem" was the main reason in roughly 4% (detrans.ai stats). These figures come from a self-selected online sample and were extracted by AI. They show recurring themes, not population rates. The realisation moments and changing beliefs pages collect more of these accounts.

Trans perspectives

Trans commenters answer the same question in several distinct ways, which roughly map onto the academic positions. Some take an innate-identity view, the version critics call a gendered soul:

Your gender identity is something you are born with and it's innate to you. If you feel like a woman, then you are a woman. —EvieFlowDDT, trans woman (MTF)

Others make the social-constructionist case, echoing Judith Butler's claim that sex itself is constructed (see queer theory):

Sex is as socially constructed as gender, because they're the same damn thing. —Gardyloop, trans woman (MTF)

Some make the reverse essentialism charge in its strongest form, linking biological definitions to patriarchy:

The core principle of partirarchy is that men and women are beings of a fundamentally different nature. Because of those differences, the two sexes have fundamentally different roles in society. —Emily__Lyn, trans woman (MTF)

The same commenter, elsewhere in the thread, says she does not believe people can change sex. Instead the brain has an "internal sense of what sex it's supposed to be" and transition matches the body to it. That is close to Bettcher's "strong" wrong-body model, and it is exactly the kind of inner essence detransitioners reject.

These views are held sincerely, and the point isn't to argue with any individual. It is that "the trans perspective" covers incompatible theories (innate brain sex, social construction of sex, self-identification), each facing different objections.

Assessment: what philosophy can and can't settle

Part of the dispute is verbal: people using "woman" in different senses partly talk past each other. But it isn't merely verbal.

1. Sex is a real kind by any serious standard. It carves nature at a joint, is anchored by gamete type, is held together by developmental mechanisms in Boyd's sense, and supports reliable predictions in medicine and biology.
2. "Gender" in the sense of roles and stereotypes is a social kind and an interactive one. It is real as social fact and changeable as social fact. Nominalists about gender, among detransitioners and feminists alike, are on firm ground.
3. The inner gendered essence is the weakest link. An innate gender that can contradict the body, revealed by preferences that are themselves culturally variable, is the one entity in this debate that resembles a real essence in Locke's sense: invisible and inferred only from its supposed effects. The most sophisticated trans-inclusive philosophers, notably Bettcher and Dembroff, do not rely on it. They argue instead from ethics, community practice and politics. That is a coherent project, but it changes the question from what people are to how they should be treated and named.

For people working through gender distress, the lesson in many of these accounts is simpler than any theory. A thin, biological answer to "what is a woman?" or "what is a man?" leaves the rest of the self open. A masculine woman or a feminine man can simply exist, without a new category, as the gender non-conformity without labels page celebrates. Philosophy can clarify the choice of framework, but not make it painless; those who found it hard deserve as much patience as those who found it freeing.

Related pages

• Philosophical frameworks and mind–body dualism
• Gender identity beliefs, intersex and DSDs and sex vs gender in law
• Queer theory, gender-critical feminism and non-binary identities

References

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