As I had said to my friend, if someone makes the claim that all swans are white and I then show them a black (or, really, any non-white color would do) swan, it is illogical for that person to stick to their claim. The claim has been falsified; they need to back down from the claim. The same holds true here. If the claim is that all people with an XY chromosome are male, then those questions I raised above need to be addressed. This, though, may actually explain why McHugh does not clearly define what he means by "biological sex." It's hard to falsify a non-specific claim.
This friend, however, in a discussion regarding same-sex marriage, told my wife, who is intersex, and I that our situation is "different." This statement has a similar problem as McHugh's claims: Different from what, exactly? What is the claim being made that this is different from?
Unfortunately, these statements of "That's different" or "That's an exception" are all too common. I recently saw a blog post that put this in a slightly different perspective:
Confirmation bias is the tendency to seek out, perceive, accept, and remember information that confirms beliefs we already hold, coupled with the tendency to miss, ignore, forget, or explain away information that contradicts our beliefs.
How many times have you either said yourself or heard someone else say, “well, that’s an exception?” Is it, or is it just data? By calling an example an “exception” you are assuming that there is a rule it violates. This is a way of dismissing information that contradicts your beliefs.
As with my swan example, the idea here that people try to cling to their claims in the face of contradictory information is the same. To put it simply, if someone says there is an exception to the rule, then the rule isn't a rule. Period. It may be a tendency (or trend) at best, but not a rule. I think that is what my friend was meaning when they said "different." But, if the case is that they were saying that our case still fits the rule, then what's the rule?
Frankly, I became much more of an advocate of gay rights upon meeting Amy and it's largely because that helped me learn that the typical rules people spout about XY chromosomes make someone male were bunk. I hope my friend can someday realize the same. Granted, though, I didn't have the extra challenge I suspect my friend has of ditching the belief that this rule is imposed by some supposedly perfect deity, meaning the rule would be perfect by extension.
I was half-way through writing this when I realized McHugh's error isn't exactly confirmation bias when I realized he isn't exactly trying to apply a rule. Rather, he's saying the rule is through biology. I.e, the rule is whatever biology determines it to be. He does not need to define this rule because it's not his job to define it. This is instead an argument from ignorance, which can be seen where he says, "No evidence supports the claim that people such as Bruce Jenner have a biological source for their transgender assumptions." I noted in my post that just because evidence has not been found does not mean evidence does not exist. The swan example still applies, but would need to be twisted just slightly to fit. Instead, one might say, "All swans are white as no evidence supports the claim that non-white swans exist." When stated in such a way, I hope the logical error becomes more apparent: that no non-white swans are known to exist is not support for a claim that all swans are white. Similarly, that no biological source is known is not support for a claim that no biological source exists. As noted in that previous post, though, that claim of "no evidence" is hogwash. Yeah, sure, there's no direct evidence to show what, exactly, may cause transgenderism in humans, but there is evidence that gender is not a binary. In humans, the existence of disorders of sexual development and intersex people demonstrates this. And here's a new one I learned about in other animals: Apparently, temperature impacts the sex of bearded dragons. Hotter temperatures tend to cause bearded dragons that are genetically male to be female instead.
This also made me remember epigenetics. This is, from what I hear from biologists, getting to be a big field of study. This field studies how environment impacts the expression of genetics. The aforementioned impact of temperature on bearded dragon may be an example of this, though it seems the environment may actually impact their genetics and not just the expression.
The larger point, though, is that there is a lot that we humans don't know yet about biology. So, for one to argue that transgenderism can't be biological because "no evidence" exists is highly irrational and shows their ignorance of biology.