Sorry this is so late. Prepare for disappointment.
If that definition sufficed for social interaction, there'd be no call for preferred pronouns.
Of course there would. Gender is not always purely objective, so we communicate things that aren't always objectively black and white. Everyday example: I'm married, but don't wear a ring. In some social interactions, I will come out and say whether or not I am married, so that others know.
An internal sense can't suffice for social interaction, because nobody else can perceive your internal senses. In order to interact with others in society, you need to account for how they perceive you.
Agreed. Telling them is a great way to enhance that perception. We communicate internal senses all day long, verbally and non-verbally.
Traditionally, this was done by making a noticeable effort to "pass" as the opposite gender. But this was back when gender was synonymous with sex, and society's gendered expectations about dress and behavior were much more rigid and well-defined.
In modern times, it's done by aping traditional gendered dress, and by outright demanding (announcing preferred pronouns, etc.) that people behave as though they perceive you as the opposite sex.
Ok, no idea how you got there. How did you determine that 'traditionally' a transwoman was sincere, but now it's just a crude 'aping'? Why were they sincere before but just apes now?
All of which is effectively meaningless anyway, since in modern times there is no overt nor expected difference in the way we interact socially with each gender. We still treat the sexes differently in some cases, but gender decoupled from sex is functionally meaningless for social interaction.
I don't know where you get this either. I treat women very differently than I do men. In limited social interactions (my experience, anyway), we are all on a more or less even playing field. But generally, I'm watching my mouth and behaviors around a lady far more than around guys. Do you occasionally urinate or disrobe at the gym in front of women? I'm guessing not, and that you actually treat them very differently. And before you say it, no, that's not some kind of gotcha for sex trumping gender. It simply shows that you do, without question, interact with the genders very differently, no matter how you define them.
For example, people don't flirt based on the other person's internal sense of gender. They do it based on their own perception of the other's biological sex.
That's not a 'for example'. As I've said many times, that's the rare exception. If you are planning to ◊◊◊◊ them or perform certain medical procedures on them, their sex matters. In the vast overwhelming times we interact, their genitalia is irrelevant.
A much more realistic definition, which does not rely on invisible internal senses, and which is decidedly un-slippery, and which has practical applications beyond social interaction, is "adult human female". The only slipperiness to it, which baffles alien space robots but is immediately accessible to beings that communicate via natural languages, is that in some contexts the definition encompasses all human females, not just the adults (e.g., women's restrooms).
Again, the core problem. 'Human' doesn't matter either, because we are not overly concerned with Koala bears in restrooms. Your flat assertion here is Woman = Biological Female. Ok. That subtly negates the whole concept of transpeople, with all the baggage that comes with that negation. It turns a transwoman, as Ziggurat has insisted, into men pretending. That's a bridge too far for me.
Nothing capricious about it. Gender and sex have always been interlinked concepts in our society. Gender decoupled from sex has no practical applications. Your actual complaint, based on your recent arguments is that we're not capricious enough in decoupling gender from sex (e.g., again, women's restrooms; the sex-based definition, applied consistently, handles this case just fine, but you want to capriciously be inconsistent in this one case).
I've said this several times: you can be definitionally linked without being synonymous. Related, or correlated, as it were. Meaningless, or almost so, if the coupling is severed, but I see no reason to sever all connection, as you assert, to have a functional understanding of gender as unique
but strongly related to sex.
We already have a hard line distinction: Adult human female.
That's one, yes.
According to this definition, it doesn't matter what you think of yourself as in the showers, but it does matter that you're showering in the sex-segregated facility appropriate to your sex.
Sez you. Which is why many see your preferred and limited definition as inadequate and denying of the trans experience. Note: yet I agree with you, but for different reasons.
As for policy: We already have very clear policy that you cannot treat someone differently in housing, employment, etc. because of their outward gender presentation.
Fairly useless in this context. If you insist on calling a transwoman 'he' at the workplace, is that person protected by policy? You seem to be leaning strongly towards removing their protections and allowing you to essentially humiliate, mock, and harass them multiple times a day at work, pointing to your definition of woman.
And note that this definition does not assail the dignity of trans-identified people. It makes no reference to, nor cares one whit about, allegations of mental illness or perversion. This entire discussion can be had - has been had, several times - dispassionately, respecting all internal senses and outward presentations, honoring the entire spectrum of human expression.
Denying their existence is not falling neatly under the 'honoring' halo from my POV.
You like to lean on policy as a talking point. Ok, clean pool. But the problem with policy is that it dumbs down the complexities of the human experience into drawing one-size-fits-all lines. The perfect everyday example is transforming into legal adult on your 18th birthday. Nothing changes, but policy intentionally dumbs it down to uselessness for the kind of nuanced discussion we are having here.