The Matter Of “Material Girls”, Part 3

If It Ain’t One Thing, It’s Another

Hand Waving To Manufacture A Binary Reality

Kim Hipwell
16 min readMar 12, 2023


This is one of a series of articles, beginning here, that discusses Kathleen Stock’s “Material Girls”.

The Central Claim And How It Collapses

The second chapter of “Material Girls” is intended to establish the reality of “binary sex”. Or more precisely, it presses:

“the claim that humans are divided into females and males, and that this binary division is a natural state of affairs rooted in stable biological fact.” [p45]

Stock quickly torpedoes her own claim by acknowledging that sex is not a natural binary division:

“if ‘binary’ means that every entity in the world must clearly fall into one state or the other.” [p59]

That’s precisely what ‘binary’ means. A binary choice offers only two options; a binary digit can contain only a 0 or 1; binary opposition is reflected in complementary antonyms that do not admit of intermediates.

A light switch
Photo by Isabella and Zsa Fischer on Unsplash

But human bodies display more than two different patterns of correlation between different sexual characteristics.¹

So, Stock is compelled to acknowledge that the implication of her central claim — that there is an clearcut definition of “sex” that gives two mutually exclusive and exhaustive ways of describing human bodies — can’t be cashed out.

Why does it matter? Because where intersex or trans people are concerned, enforcement of the idea that binary sex is “reality” — that only two specific patterns can be applicable — can have devastating results.

Elsewhere, rejection of this model is due to recognition that it only approximates a more complex reality:

  • the processes involved in sex differentiation can have a variety of outcomes
  • gender transition has a wide range of material effects, such as the effects of hormone therapy on secondary sex characteristics²

But “Material Girls” insists otherwise; this equivocation about the meaning of “binary” is used to slur over the complexity apparent in the diversity of human bodies, suggesting that a simplistic abstraction of sex — a naive folk theory — actually corresponds to a precise description of “material reality”.

The Bigger Picture

Stock invokes “stable biological fact” within her central claim, to frame herself as a defender of fact against fiction.³

But how a “binary division” of sex is “rooted” in such facts is never established satisfactorily in any of Stock’s three accounts (pp45–53):

  • The “gamete account” relies on unverifiable counterfactuals and teleological reasoning.⁴
  • The “chromosome account” has fundamental problems which are necessarily also present in broader genetic accounts.⁵
  • The “cluster account” presents a more sophisticated form of essentialist categorisation⁶; however, there is no reason to assume that binary sex will naturally emerge from a clustering process.⁷

The fact that three different incompatible accounts are given implies that there is no single principle that accurately draws a dividing line between sexes. Indeed, Stock ultimately endorses the position that sex can be conceptualized using different dividing lines between “male” and “female”, stating that where the line is drawn is:

“in a sense a practical decision, to be made in relation to wider theoretic goals” [p52]

So, drawing a binary division between sexes does not entirely reflect a “natural state of affairs”, but relies on a sharp-edged border being drawn through regions of ambiguity by the imposition of social conventions. This is unavoidable, because of the inherent blurriness of biological categories.⁸

How such “wider theoretic goals” affect sex classification is extensively discussed by the philosopher Sally Haslanger in Theorizing with a Purpose: The Many Kinds of Sex. In that article, Haslanger discusses the inescapable importance of a “framework of social meaning” in defining how we differentiate between “male” and “female” — even in situations when we take that distinction to be grounded solely in physical difference. Different frameworks suggest radically different boundary lines.

This image shows the border between Belgium and Netherlands in Baarle-Nassau, and illustrates how complex borders can be. This shows Belgium territory contained in 16 enclaves that are entirely surrounded with Netherlands territory; within some of those Belgian enclaves are 7 counter-enclaves, areas of Netherlands territory entirely surrounded by Belgian territory.
Enclaves and counter enclaves constituting the complex border between Belgium and Netherlands in Baarle-Nassau. Original image By Tos — Own work, Public Domain,

Once we recognise that “social meaning” is inherent to the definition of sex, then notions of sex and gender seem necessarily intertwined: both are socially driven ways of classifying people that stem either from a blurry first-order distinction based on the possession of of specific physical characteristics, or even blurrier higher-order reflections on that first-order distinction.⁹

In fact, various conventionalist and constructivist positions highlight that there’s not only an ill-defined boundary in play, but that there are also many examples of cultures that draw sex/gender boundaries in an altogether different way, using criteria that weigh such “stable biological facts” differently.

For example, it’s perfectly workable to operate with an octonary distinction, a quinary distinction, or a unary lack-of-distinction, without any requirement for “biological facts” to be swept under the carpet.¹⁰

Stock dismisses such elaborations upon what “practical decision, to be made in relation to wider theoretic goals” might look like with breathtakingly gauche strawmanning and vitriolic characterisation.

For example, she describes Judith Butler as an:

“intellectual behemoth in the world of sex denial” [p60]

And continues with the ludicrous framing that their constructivist position is necessarily equivalent to an assertion that:

“not only that there are not two naturally pre-given, stable biological sexes, but also that there are no pre-given facts about natural selection. There is no sexual reproduction. There are no pre-given chemical elements or biological species. […] There are no molecules, atoms, or quarks. […] Creationism is neither worse nor a better theory than Darwinism.” [p63]

But this only serves to highlight that the quality of Stock’s argumentation is awful: this is a preposterous argumentum ad lapidem. The crude smack of boot leather on boulder is no more more philosophically informative than it ever was.

No one thinks that, for example, the diversity of colour terminologies in different languages affects the electromagnetic spectrum.

Cladistic taxonomy tells us that there is “no such thing as a fish”, but holding this belief doesn’t require an insistence that the entities we folk-theoretically describe as fish don’t literally exist, nor does it require repudiating the existence of chips, the digestive system, or the general theory of relativity.

A portion of fish and chips
Photo by Meelan Bawjee on Unsplash

Likewise, demurral from a crude “common sense” brand of natural kind realism about “biological sexes” is not equivalent to dismissing scientific explanations; and characterizing all forms of constructivism — a major current of thought within philosophy — as a ride down a slippery slope to ontological nihilism¹¹ is just intellectually feeble.

Thomas Laqueur gets the exact same treatment as Butler. His discussion of incommensurability, a familiar concept in the philosophy of science, is framed as support for a crude notion of theory creating reality:

“Do big differences between ancient and modern conceptions of cancer mean present-day cancer was invented by scientists rather than discovered by them? […] Were there no black holes before Einstein’s theory of general relativity predicted them?” [pp68–69]

All of the absurdity here is entirely resident in Stock’s garbling of the idea of competing paradigms.

The philosophically naive might be convinced by the immolation of these strawmen, or by Stock positioning herself as sole arbiter of what material reality consists of. A sterner evaluator would pause to note that Stock’s own statements mean that the difference between her own position and those she attacks so vehemently is one of degree, not of kind.


It might seem odd that Stock accedes to the fundamental challenges to a binary model of sex while regarding them as basically unimportant.

But the game here is to dismiss the “blur” of intersex and trans existence as mere statistical noise, treating scarcity as a proxy for immateriality and insignificance. Likewise, any harm resulting from playing that game.

The trinitarian credo that this chapter defends — “sex” as real, binary, and immutable — is, as we have seen, far from incontrovertible. And it’s important to push back against this idea, because it’s a standard pretext for harmful anti-trans campaigning:

  • It’s the basis of claims that gender transition is immaterial, meaningless, or impossible
  • Which are used to fuel insinuations that being trans is therefore a form of derangement or delusion (Stock uses the euphemism of “immersed in a fiction”)
  • And that idea, in turn, is used to justify actions intended to strip away societal support for trans people, including medical care and any legal basis for transition

We’ve already seen Stock advocating for those kinds of actions in Fabricated Identity.

More broadly, removing human rights from transgender people — all for the good of ourselves and/or society, of course — is precisely what’s demanded by the grossly transphobic WDI “Declaration On Sex-Based Rights Of Women”.¹² Note the “sex-based” here — this all is hinged on the kinds of arguments Stock is making in this chapter.

The position of the WDI is most plainly stated in this submission to UK parliament by the organisation who set up the Declaration, which straightforwardly says that they are calling for the elimination of “the practice of transgenderism”.¹³

Stock was not only one of the earliest signatories to the WDI declaration, but is also directly quoted on the WDI’s website.

One might well feel that the metatextual framing of “Material Girls” as the work of a philosopher providing an intellectually rigorous two-fisted counterblast to unreasonable ideas is rather undermined by the observation that its author is openly signed up to a petition that advocates for the elimination of trans existence.

Next Article

The next article in this series is Mother’s Ruin.



This observation is sometimes taken to show that sex is “bimodal” rather than binary. (See here for a description of bimodal distribution).

One spurious objection often made to bimodality as a model of sex is that there is no single scale for the possession of sexual characteristics to be measured on. No such scale is needed: bimodality can obviously emerge in multivariate distributions.

Stock’s “cluster account” of sex follows this basic idea; we’ll consider this further below.


Just before the conclusion to this chapter, there is a section in which Stock produces a fiat declaration that physical changes wrought by gender transition are immaterial to any definition of sex:

“None of the features cited as essential to or otherwise relevant for sex category membership … can be artificially produced through hormone treatment or surgery or anything else.” [p73]

The fundamental problems with her accounts of “sex category membership” will be considered below. But it’s very telling that here Stock attempts to justify this declaration by focusing on a feature that clearly isn’t pertinent to any of those accounts, average breast size:

“Breasts acquired by trans women through hormone treatment are on average very modestly sized (one study reported changes ‘mainly resulting in less than an AAA cup size’) and usually require silicon augmentation to reach desired proportions, making them compositionally and functionally different from endogenous ones.” [p74]

(The fact that ‘silicon’ is a substance very different from ‘silicone’ might lead one to question the thoroughness of Stock’s expertise/research here).

This doesn’t even qualify as a bad argument: it is simply an evocation of queasiness caused by the mere contemplation of trans bodies, a ham-handed kind of othering.

Average breast size or augmentation are clearly irrelevant to “sex category membership”. The number of trans women who undergo breast augmentation procedures is vastly outnumbered by cis women who do; none should have a question mark hovered over their “sex category membership” as a result. The breasts developed by cis and trans women don’t have fundamental differences.

(Lest one question the significance of breasts, Stock bolsters her point with a brief consideration of the quality of the arm fat of trans women after a year of hormone treatment: we’re almost recapitulating Ancient Greek conceptions of the fundamental differences between male and female flesh at this point).

None of this bodes well for Stock’s claim that:

“making a distinction between endogenous and artificial parts of a sexed body serves various legitimate explanatory purposes we can’t do without” (p74)

While she promises to redeem this claim in Chapter 3, she simply reiterates the idea:

Endogenous features count as an important baseline in specifications of human health. It’s not the only baseline; as noted earlier, disease can be endogenous too. (pp80–81)

So, what is “natural” is good in establishing a baseline, except where it should be discounted (in which case, we call it disease), or where something else might be important. Which leads to this zinger:

“Artificially altering some natural feature in an organism comes with knock-on effects for other features, bad as well as good”. (p81)

In other words, Stock has discovered that medical treatments can have side effects. This is hardly startling. (And, of course, endogenous factors such as aging are also used to modulate baseline expectations, as Stock approvingly notes in the run up to this).

All of this huffing about artificiality is no more than a bog-standard appeal to nature. But this is dangerously used to advocate that we might ignore medical history and treat trans patients as if their bodies conform solely to the typical patterns of one side of a “binary sex” model; they clearly do not.


This is particularly noticeable in Chapter 6, which literally argues that everyone that disagrees with Stock’s position is saying things that they don’t really believe (because common sense says they can’t possibly).

That chapter, framed around the topic of fiction, stands out as one of the more risible intellectual lowpoints in a book jammed full of them.

(Aesthetics, particularly philosophy of fiction, is Stock’s field of expertise; she is a defender of extreme intensionalism, an interesting position to contemplate in the light of her insistence that biological fact can only be interpreted in one way).


The “gamete account” of sex suffers from the glaring problem that some people don’t produce gametes. This hole in the account is patched up by assuming what we might call subjunctive gametes for those people — gametes that their body would have produced if things had turned out differently — and taking those to define sex.

But saying that everyone is somewhere on a “pathway” to some particular mode of gamete production is no more valid that saying that everyone is on a “pathway” to becoming a portrait painter — even those who’ve never touched a brush. On what basis?

The patch up embodies a classic fallacy — the injection of teleological assumptions into biology (see here). This is apparent in Stock’s description of development that can “go awry” or turn out “according to plan” (and, very specifically, in her attempt to arbitrate using such assumptions on p45).

In reality there is no plan — and therefore no principled way to decide a subjunctive outcome to development — what “should” have happened — such as whether an ovotestis was “really” destined to be an ovary or a testis.

Not only does this subjunctivism rely on the implict assumption that nature is goal-driven; it also insidiously frames the purpose of human bodies and therefore human existence as reproduction — an idea that fuels far right anti-feminist ideologies such as pronatalism and is an omnipresent theme within homophobia.

(For examples of this framing in Material Girls, see p76, p92, and p98 on the importance of procreation for the survival of the human race, or pp98–102 and pp156–158 on womanhood conceptualized as motherhood).


The “chromosome account” is fundamentally an appeal to the naive idea that a pair of “sex chromosomes” determines sex, with a clear cut mapping from an XX pair to female and an XY pair to male.

However, there are numerous exceptions to this pattern. The relationship between karyotype and phenotype displays a complexity that has doomed attempts to use such accounts as an operational definition of sex in sports governance.

It is sometimes suggested that a more sophisticated general “genome account” would work in its place. So, let’s consider the idea that there could exist a function to divide the set of all possible genomes into two subsets — male or female. This function would take into account translocation of the SRY region, the existence of genes for androgen insensitivity, and so on.

There would still be two fundamental problems.

Firstly, DNA is not a blueprint: this function can’t give us a universal account of biological sex because developmental occurrences such as mutation and mosaicism exist; in many species, environmental sex determination also determines the outcome of development.

Nor does it take into account epigenetics, the modulation of gene expression caused by environmental factors, such as hormone levels.

(As with the gamete account, teleology has crept in, this time via the assumption that a specific genome is designed to reach a specific outcome).

Secondly, even if we put development to one side, we must first have a phenotypic definition of sex in order to know what the developmental outcome of a specific genome actually is. If we don’t know how to distinguish between effects, we can’t connect them to causes. Knowing what a genome sequence is doesn’t, by itself, lead to any clarity about which sex its bearer should be classified as.

This is a fundamental question that all “sex testing” runs into: which phenotypes belong to which sex? Knowing a karyotype, or even an entire genome sequence, does not provide an answer. We cannot “read off” a sex from a genome directly; DNA does not define it for us.

(The same confusion between causal factors and definition renders otiose Stock’s invocation of cause on pp54–55: quotidian accounts of sex are naturally based on observeable features, not on unknown or unknowable factors. Note that Stock flips to this exact inverse position on pp93–94).


The “cluster account” makes use of the notion of homeostatic property clusters — HPCs — is presented by Stock as an alternative to essentialism:

Unlike on the gamete or chromosome account, though, on the cluster account, no individual characteristic is treated as essential for being female or male. [p52, emphasis in the original]

But HPCs still embody a form of essentialism, as per the originator of the term:

I’m offering an alternative approach to the problem of essentialism. I’ll argue that species (and probably some higher taxa) do have defining real essences, but those essences are quite different from the ones anticipated in the tradition that Mayr, Hull, and others criticize

[from “Homeostasis, species and higher taxa” by Richard Boyd]

Stock never considers anti-essentialist accounts of conceptual structure, which require no overlaps in features between category exemplars (a notion famously discussed by Wittgenstein in his examination of what constitutes a “game”, which introduced the notion of family resemblance patterns of word meaning).

This is a significant oversight, which undermines much of what Stock later says about the meaning of “woman”: this is analysed in more detail in the review of Chapter 5.


Richard Boyd introduced a notion of HPCs as a way to provide a stable footing for the idea of “natural kinds” in the face of taxonomic ambiguities in biology (particularly in relation to the concept of species).

However, an HPC account does not imply that that there must be a sharp boundary between natural kinds; nor does it require that ambiguities of classification will cease to exist. (It is more interested in underpinning the notion of “natural” relatedness than in determining what forms a “kind” must take).

Cluster analysis of data takes many different forms, and so always requires operational decisions: choosing which features to measure, deciding on a similarity metric, selecting the algorithm used to generate clusters, and so on. This does not necessarily result in mutually exclusive and exhaustive classification of all data points: algorithms that allow for partial clustering, overlapping clustering, or fuzzy clustering are all possibilities.

In other words, there is no reason to suppose a binary would be naturally emergent from such an analysis, as opposed to a bimodal distribution, or another, more complex, clustering.

Likewise, a species division between lions and tigers, presumably explainable with an HPC account, does not preclude the existence of ligers or indeed tigons, literal intermediates. Stock herself refers to such ambiguities on p58, shortly before she equivocates over “binary” on p59.

A photograph of a liger, which resembles both lion and tiger


Stock reiterates this point throughout the chapter. For example:

“The lines of these accounts are not completely clean” (p48)


“difficulties about borderline cases is absolutely standard for biological categories” (p58)


“There will obviously be cases that don’t clearly belong to either, or seem to belong to both” (p58)

So much for a binary division being a “natural state of affairs”.


It’s unsurprising that concepts of sex and gender are commingled, given that both concepts were once solely encompassed by the word “sex”, that the two words are still used interchangeably in common and legal usage, and that many other languages do not even draw this distinction.

Gender critical arguments often work from the assumption that there is a clean separation between the two; but this isn’t borne out in general usage.

The insistence that sex and gender cleanly separate along “biological” lines is integral to Stock’s program: insisting on the unreality of gender alongside the reality of sex is the key to insisting on a “biology is destiny” justification for the naturalness of gender divisions, as will be seen when looking at the other chapters.


Stock mentions some other examples in passing on p35, solely to be dismissive of them at speed; she lumps all forms of gender variance together as part of an “explosion of identities”.

A severe colonial bias is revealed by this airy dismissal of a multiplicity of social contexts as though they are frivolous or faddish.


Ontological nihilism is a real thing, by the way (irony intended).

But this argument is very far removed from the historiological, sociological or anthropological concerns of Fausto-Sterling, Butler, Lacquer, Oyěwùmí, or indeed any other scholars of sex and gender.


The WDI was formerly called the WHRC (Women’s Human Rights Campaign). These are unwarrantedly grandiose names for what is simply a tawdry crusade against human rights.

The anti-human rights nature of the declaration is condemned by the Association for Women’s Rights in Development here; a detailed and damning analysis of the WDI Declaration by a human rights lawyer can be viewed here; more analysis from Trans Safety Network is available here.

The Wikipedia article on the declaration, with additional context, is here.


I wrote an article called Schrödinger’s Drag, which might be a useful read for anyone who has fallen for the bizarre line that trans people, specifically, reinforce gender stereotypes to a greater extent than cis people do.



Kim Hipwell

PhD in Cognitive Science, interested in the structures of natural and artificial languages. Thrives on atonal music and trans rights. She/her.