Transgenderism presents intersex people, that is, people with CCSDs (congenital conditions of sexual development), as evidence that there is no absolute male/female binary. If it’s really true that there is (or was) even a single human who does not fit the binary, then the absolute is shattered.
Abigale Favale’s book The Genesis of Gender does a good job of pointing out that research suggesting that 1.7% of people are intersex is disingenuous. However, even with a more medically precise definition, it’s true that some 0.02% of people have both male and female sexual characteristics, such that their sex is not easily assignable at birth. Even this 0.02% is more than enough to achieve transgenderism’s goal, because all they’re looking for is one individual.
But Favale goes deeper on pages 127-129 of her book:
In the remaining [0.02%] outlying cases, the reality of sex is still present but must be more carefully discerned—not for curiosity’s sake, but in order to support the person’s physical health. This is not because those individuals are neither male nor female, but rather because their developmental pathways of becoming male or female took some unexpected turns.
Discerning sex in these individuals entails looking at multiple factors taken together: karyotype (chromosomes); phenotype (genitalia); gonads (ovaries or testes); internal structures that support gamete production; and hormones… Sexual ambiguity occurs when the phenotype is not readily classifiable as male or female, or when the karyotype is not consistent with the phenotype. Overly broad use of the term “intersex” tends to privilege karyotype and phenotype , while overlooking gamete production and the structure of the body as a whole…[but] gamete production is the foundation of biological sex.
This reflects a common error: reducing biological sex to secondary sex characteristics—seeing sex as merely about genital appearance or breast development. The gender paradigm fundamentally misunderstands what sex is, confusing cause with effect. Secondary sex characteristics develop as a consequence of sex; they are the effect, rather than the cause.
…When faced with ambiguity at the level of phenotype and karyotype, the best response is not to shrug and embrace the spectrum, but to continue the discernment of sex by looking at the anatomical structures that support either large gamete production or small gamete production. Although the term “hermaphrodite” used to be applied to cases of sexual ambiguity, this is a dehumanizing misnomer. Hermaphrodites are species that do not have separate sexes, such as snails and slugs; instead, each member of the species has the ability to produce both large and small gametes and can thus take on either the “male” or “female” role in reproduction. For this kind of species, hermaphroditic reproduction is the norm. Human biology, on the other hand, does not support this model of reproduction. In the rarest CCSD, an individual can develop both ovarian and testicular tissue, but even in this case, he or she will produce one gamete or the other, not both. There have been only about five hundred documented cases of an ovotesticular CCSD in medical history, and there is no direct evidence in the literature of a hermaphroditic human being, someone able to produce both small and large gametes. [Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6737443/]
When all the dimensions of sex are taken into account, sex can be discerned in each human being. To conclude otherwise is to exclude some individuals from a reality in which we all participate.
Thus, Favale argues that a person’s sex must include consideration of whether they produce large gametes (eggs) or small gametes (sperm). This is crucial for her understanding of sexuality. She later defines men as people whose bodies are organized around the ability to be the reproductive donors, and women as people whose bodies are organized around the ability to be the reproductive hosts. A person’s maleness or femaleness involves the totality of biological factors related to one or the other of these reproductive roles (even if they are infertile).
With this definition, Favale is able to defend the male/female binary by claiming that “there is no direct evidence in the literature of a human being who is able to produce both small and large gametes”; even the 500 people (ever!) who have had both ovarian and testicular tissue will produce only one or the other. It remains either/or.
Every human is either male or female. No human is neither. No human is both. There is no third option.
As an addendum, I’d like to point out that it’s important to include “no human is both.” I know of a teacher who, being probably unaware of how Favale successfully defended the inner keep on this issue, has attempted to resolve the question of the 0.02% by denying “a third sex,” but offering instead that we are either “male, female, or both.” But if someone can be both sides of a binary, then it’s not a real binary—not an either/or, not a mutually exclusive dual categorization. If people can be both, then transgenderism still wins, because that premise can be extrapolated to almost all their other conclusions. If the circuit is on, or off, or both on and off, then we do not have something we can build a circuitboard with. If you are male, or female, or both male and female, then we do not have something we can build a Genesis view of sexuality with.