What fallacy is this transphobe making?

So there is this guy arguing against the legitimacy of Trans people, who's definition of women is

A person born with XX chromosomes who is of the nature to give birth.

 

I pointed out that this excludes infertile women and he responds:

I said is of the nature to give birth. Infertility among women is the exception that proves the rule. The fact that a women goes to the doctor to try and fix it implies that she is supposed to be fertile. 

 

A man who can't give birth wouldn't even think to go to the doctor to see why he can't give birth. Because he is not of the nature to give birth.

 

What fallacy is he making here?

The argument presented involves several logical fallacies and poor reasoning. Here are the key issues:

1. **No True Scotsman Fallacy**: This fallacy occurs when someone's qualifications for membership in a group are arbitrarily changed to exclude counterexamples. Initially, the definition provided for a woman is "a person born with XX chromosomes who is of the nature to give birth." When challenged with the example of infertile women, the speaker shifts the criteria subtly by saying that infertility is an exception that "proves the rule." This adjustment conveniently excludes infertile women from undermining the definition, making the argument non-falsifiable and inconsistent.

2. **Begging the Question**: The argument assumes its conclusion in its premises. The definition provided presupposes the very criteria (chromosomes and ability to give birth) being debated about who qualifies as a woman, especially in discussions about transgender identities. By doing so, the argument circularly defines "woman" without addressing the broader societal and biological complexities, thus failing to engage with the central issue.

3. **Hasty Generalization Fallacy**: This fallacy involves making a broad claim based on insufficient evidence. The definition of a woman as someone who is "of the nature to give birth" ignores the wide range of biological, medical, and social realities that can affect this ability and does not account for those who do not fit neatly into these categories.

4. **Appeal to Nature Fallacy**: This argument claims that a woman is "of the nature to give birth" and that implies some natural state or essence of being a woman. This is problematic because it suggests that what is "natural" is inherently correct or better, which does not account for the diversity of human experiences and conditions.

These fallacies combined show a lack of nuanced understanding of gender and biological science, and they undermine the validity of the argument.

I don't see a fallacy at all, except in your introducing the claimant as a transphobe (ad hominem guilt by association).

it may not be politically correct. But as you have laid it out he is basically giving the physiological definition of sex and not gender. Nowadays, there's a controversial attempt to restructure gender identity. So there might be a potential equivocation discrepancy in your dialogue, but no inherent fallacy.

"A person born with XX chromosomes who is of the nature to give birth."

Whether this statement is a fallacy depends on the context of the conversation. Therefore, this falls under the heading of poor communication. Humans have 23 pairs of chromosomes, or 46 total, and 22 are numbered chromosomes, known as autosomes. The 23rd pair is a pair of sex chromosomes (XX or XY), which determine whether you’re biologically male (XY) or female (XX).

What a person self-identifies as is not important. The person is what it is: male or female. I might self-identify as a muskrat, but that does not make me one.

Starting with his definition, I see two issues. One, using XX chromosomes as part of the definition. Even if you're discounting trans women, there are intersex conditions that will cause someone is a physiologically a woman to have chromosomes other than XX. The second part, "of the nature to give birth" is committing the ambiguity fallacy . It is pretty unclear exactly what that is supposed to mean, allowing this person to tailor their definition in response to any criticism.

So, when they are pressed, they use the phrase "the exception that proves the rule," which is a commonly used phrase, but one that really runs counter to logic. Sure, some rules can be complicated and require caveats. But others are ironclad and would only be weakened by the existence of exceptions. For instance, the law of conservation of energy, or "Tourists at Yellowstone must not try to pet the bison." This person might be committing the overwhelming exception fallacy here. But, if they are trying to create a rigid definition in order to categorize things, but then creating exceptions, the definiton becomes increasingly meaningless and the categorization becomes more subjective.

"The fact that a woman goes to the doctor to fix it proves that she is supposed to be fertile" has a couple issues. There may be stereotyping (the fallacy) at play here, as it's implied that all infertile women seek infertility treatment. There are a number of reasons why a woman would not, such as not having access to such care, not realizing that she's infertile, or just not wanting children.

Additionally, this person is using the naturalistic fallacy here, by making the claim that women are "supposed to" be fertile. Most women are, but the fact is that nature isn't sentient, doesn't have a plan, and produces a lot of variety and what we might consider imperfections within humans.

And, finally, the idea that going to a doctor to fix an issue proves this is just a non sequitur . In the 18th century, a woman may have seen a doctor to fix the issue of her humors being out of balance. Today, a woman might see plastic surgeons because she wants to look like a living Barbie doll. While doctors do rely heavily on science to improve people's quality of life, there have also been time where medical science has reached incorrect conclusions, and when the goals of medical care are driven by things like cultural norms.