Today on X, I ran across a conversation between a woman who wanted to know why women should be forced to undress in front of men in female-only spaces and a man who insisted that individuals identifying as the opposite gender are in fact the opposite gender. This is an obvious falsehood, and it is upon this falsehood that gender ideologues demand the inclusion of males in female-only activities and spaces. The man presented no argument not because he was not up to the task—nobody is up the task because there is no rational substance to marshal for it. However, defeating gender ideology requires not only insisting on biological truth, but on making sure public policy concerning gender-segregation in society is based on that truth and not on ideology that denies it.
The power of gender ideology in undermining the science of gender and women’s rights is part of a larger problem: science denialism. A rational secular society must be one that accepts science as a vital part of public policy and the delineation of rights. To delineate something means defining and describing something with clarity and precision. That involves drawing boundaries around or specifying the characteristics of a thing to distinguish it from other things. These boundaries and characteristics are objective, i.e., independent of the mind. Science is the superior way of determining the boundaries and characteristics of things that exist objectively.
Recognizing the role biological science plays in the determination of truth is not a presumption that scientific truths are fixed; science is an open system where claims are subject to scrutiny and disconfirmation. Rather, the establishment of science requires that the truth of the gender binary must be disconfirmed before policies based upon it are replaced. More than this, the claim that a man is a woman because he says he is must be supported by positive science. Given that such a claim is subjective, and that objective claims about gender that contradict science are easily disconfirmed, it is at present impossible to see how gender ideology can replace the science of gender. One can only do this by rejecting science.
Sal Grover’s commentary in the tweet I share below is thus on point. “If I was going to go on national television to say that women should accept men in women’s spaces, you better believe I’d make sure I had a good argument for it,” she writes. “But because there isn’t a good argument for it, everyone who does it ends up making a complete fool of themselves.” As a college professor, I am surrounded by administrators, faculty, and students who believe that women should accept men in women’s spaces. They justify this belief by asserting the same claim as the man in the video. But it is always only an assertion, asserted by someone who refuses to admit the science of the matter. Since the claim is false, and since I don’t want to simply assert something, I thought it would be useful to explain why.
Gender (or sex) determination in humans (and other mammals) is guided by chromosomal karyotypes, specifically XX and XY configurations. The presence of the Y chromosome plays a pivotal role, as it carries a critical gene called SRY (sex-determining region Y). This gene, when functional, directs the development of male reproductive tissues, leading to the production of small gametes known as sperm (or spermatozoa). In the absence of the Y chromosome, as in individuals with an XX karyotype, reproductive tissues develop to produce large gametes called eggs (or ovum). Occasionally, the SRY gene on the Y chromosome may not function properly. When this occurs, the reproductive tissues are unable to produce either sperm or eggs. Sometimes monotremes (echidnas and platypuses) are held up as examples of mammals that do not fit this model. However, even in monotremes, gender is binary; despite their unique system of gender-determining chromosomes, monotremes still produce individuals that develop as either male or female. There are no exceptions to the rule.
This is also true of birds, although sex determination operates through a different chromosomal system known as the ZZ/ZW system, the reverse of the system found in mammals. In the avian system, females are the heterogametic sex (ZW), while males are the homogametic sex (ZZ). The presence of the W chromosome determines female development, whereas its absence leads to male development. In birds, the DMRT1 (doublesex and mab-3 related transcription factor 1) gene, located on the Z chromosome, plays the critical role in male development. Because males have two Z chromosomes, they express more of this gene, which promotes the development of male characteristics. In females, who have only one Z chromosome, lower levels of DMRT1 and the presence of the W chromosome drive female differentiation. To be sure, there are complexities in avian biology. For instance, cases of sex reversal have been observed, typically influenced by environmental and hormonal factors rather than chromosomal anomalies. However, as with mammals, these exceptions do not negate the fundamentally binary nature of gender in birds.
In fact, the gamete system is fundamentally binary across all animals and plants (so I need not go through the reptile, fish, insects, and all the other varieties of life). In all sexually reproducing organisms, there are two types of gametes. This distinction defines the binary nature of gender at the gamete level and underpins the biological classification of male and female across species. This binary system arises in natural history (evolution) from the fundamental constraints of reproduction; small gametes are optimized for mobility and quantity, increasing the likelihood of fertilization, while large gametes are optimized for nutrient provision, ensuring the initial support of a developing zygote. This complementary strategy has evolved independently in many lineages because it is highly effective for sexual reproduction. Evolution is not intentional but it is remarkably rational.
Putting the matter simply, the gender binary is a feature of the chain of life across these kingdoms, whatever the variation in how these gametes are produced and distributed among individuals. Even in cases where secondary sex characteristics, reproductive roles, or chromosomal systems introduce complexity or variation within species gender remains binary.
This is an essential biological truth; it cannot be changed by ideology. Rejecting biological science only makes a person unscientific in his thinking. It does not change reality. It will not do to say that a man who claims he is a woman really is one and therefore should be allowed to participate in activities and be present in female-only spaces. If this demand proceeds on the ground of truth, then it must advocate for eliminating sex-segregated spaces altogether. Otherwise it is entirely arbitrary. Why women must accept men in their activities and spaces must proceed via a different argument, for example that individuals should have access to the same activities and spaces regardless of their gender. This argument proceeds on the grounds of strict equality of treatment, which must eschew recognition of grouped differences. If this is accepted, the principle of equity is abandoned. As it stands right now, the gender ideology crowd wants the have their cake and eat it, too.
Equity is why gender-segregated spaces exist in the first place. Gender-segregated spaces were established because they provide comfort, privacy, and safety in settings where material differences between males and females can have practical or social implications. In changing facilities, locker rooms, and restrooms, segregation generally ensures personal privacy during such activities as attending to hygiene needs. In sports, gender segregation allows for fair competition by accounting for physiological differences, such as muscle mass and strength, that can influence performance. In gender relations, it protects women from male violence, which has a profound and devastating impact on females. Male violence perpetuates gender inequality and undermines women’s autonomy, safety, and well-being. Victims may suffer long-term physical injuries, mental health challenges such as anxiety, depression, and trauma, and a diminished sense of self-worth. These effects perpetuate a cycle of fear and marginalization, as women feel and are unsafe in areas of life where they are especially vulnerable.
Even if there are women who don’t mind men in their spaces, the fact that there are women who do is sufficient for maintaining gender-segregated spaces. Likewise, the fact that not all men harass or perpetrate violence against women does not negate the fact that some do, including those men who claim to be women, and therefore the safety of women depends on the integrity of these spaces. The woman in the video makes several important points, one of which is the question of why it should be men who decide the fate of women. For that matter, why should some women decide the fate of all women?
Throughout this essay I have used gender and sex interchangeably. This is because, as I have shown in numerous essays on Freedom and Reason, they are synonyms and have been for eight centuries. I have shown on this platform that biologists still use the term gender in describing reproductive anatomy and processes. Moreover, I have documented the rise of gender ideology and the political project to falsely divorce gender from sex by arbitrarily changing the definition of the former and appealing to the subjective construct of gender identity. Disconfirmation requires identity to be an objective thing, this so we can determine what sort of thing it is.
There is no evidence in science that validates the claim that a person can be born in the wrong body, and it is difficult to imagine how this could even be possible given the fact that the brain of a male is by definition a male brain, this because the brain in question, like the heart, kidneys, and everything other organ and system, exists in a male body, however it may appear in a scan. That grouped differences come with trait variation in the myriad of attributes that delineate the gender binary does not obviate the qualitative differences inherent in sexual dimorphism. Moreover, altering physiology chemically or changing its appearance cosmetically through surgery doesn’t change what the organism is genetically. Those interventions only simulate gender. Simulations of things are not the things themselves. When they are not used to predict the working out of a theory, they are deceptions.
If reason and science were followed, there would be no controversy concerning gender since this whole thing would have been over before it started. But, over a period of decades, anti-science sentiment infected the thinking of those whose hands grasp the levers of power, and through this power an ideology has emerged that misleads people into believing impossible things. It is in this sense that I describe gender ideology as a religion. Unfortunately, it is a religion that state respects, which, considering the separation of religion and public policy articulated in the First Amendment to the United States Constitution, it should not. The relevant clause in the article is specifically worded this way: “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof,” and the free exercise piece requires freedom from its exercise.
The other items in that same article, the rights to freely speak and publish, are necessary conditions for the advancement of science. The goal of establishing a secular republic for the advancement of science and technology was paramount in the intent of the Founders. If they were alive today and looked at the corruption of our sense-making, law-making, and policy-making institutions by gender ideology they’d ask when America lost the plot. My essays on Freedom and Reason explain how this happened. My commitment to science compels me to do this work. But I cannot alone push ideology out of our sense-making institutions and governmental agencies and set the nation back on the path of enlightenment. That will require those of us who work from reason to pull together. It’s not that a man should be punished for claiming he is a woman. It’s that women shouldn’t be punished because he does.
freedom and reason 
Well said. I think there is a battle to be fought on two – fronts. The battle against biological denialism and blank slate thinking, and also the dismantling of the concept of “gender identity”. I am increasingly inclined toward the idea that “gender identity” is essentially just a confused view of what we always used to call “personality”. I think there are some good reasons to believe this – one being that the word “personality” seems to have all but disappeared from discourse – especially the discourse of gender identity advocates. This hypothesis also explains the ever-growing list of “genders”, since a single word or term will never adequately represent how a given individual sees themselves. It also explains why non-sexual themes have crept into gender ideology – since personality is about more than sex. This hypothesis might also explain why pubescent individuals are so easily duped into embracing gender identity ideology, because puberty has always been a time of burgeoning sense of one’s own personality. Once teachers started labelling this process of blossoming and self-discovery as “gender identity” rather than simply “personality”, it’s off to the races.