Pretty easy to answer. A women is someone who can naturally create a child inside of them, or naturally possesses the organs to do so.

It’s amazing our collective intelligence has dropped this far. We solved this problem quite a long time ago…

Are people with Müllerian agenesis not women then? Your definition doesn't seem to match up with colloquial usage, even ignoring trans women.

https://en.wikipedia.org/wiki/M%C3%BCllerian_agenesis

Contra:

> The first, preferred by Fowler, is that the presence of an exception applying to a specific case establishes ("proves") that a general rule exists. A more explicit phrasing might be "the exception that proves the existence of the rule".[1]

* https://en.wikipedia.org/wiki/Exception_that_proves_the_rule

Or perhaps:

> The phrase means that an extreme case is a poor basis for a general law that would cover a wider range of less extreme cases. In other words, a general law is better drafted for the average circumstance as this will be more common.[1]

* https://en.wikipedia.org/wiki/Hard_cases_make_bad_law

Further it can be argued that the fact that a defect is present in the biological system does not invalidate the presence of said system generally. The complete lack of a system could be the determining factor.

If someone considers themselves a woman, they are a woman. It doesn't have to be any more complicated than that for 99% of life. I can understand some objections in a very limited number of contexts and sports is one of those contexts, but otherwise just allow people to choose where they fall on the gender spectrum.

What makes 'woman' a special class in this regard? We wouldn't accept the same kind of self definition elsewhere. I couldn't decide to be a Native American without meeting some external criteria around my birth and life. Nor can I decide to be 6 foot 4 or thin even if I sincerely believed it. Someone who did self define like that would be regarded as delusional.

Is there some principled way to decide what things one can self define as and which one can't?

This is a difficult topic. A key difference between your example of height and something like gender is that gender is socially constructed, while height is a physically reality that can be objectively verified. So one part is that it has to be socially constructed.

However, race is also socially constructed, so it's tricky. People who claim to be "trans-racial" are still regarded as delusional by society despite this. This is mostly just the position of the society we are in.

But there is something more that makes gender transition more valid than racial "transition": Gender dysphoria is a real condition, that has the medically recommended solution of social and medical transition. This is a good reason for why society should adjust it's social construction of gender, and this is why it is happening right now. To date, "race dysphoria" is not medically recognized and has not been formally observed. It has no history dating back hundreds of years like being transgender does.

I largely agree, but I will add that we generally do allow people to self-identify their race. Lots of college and job applications that ask for your race will use this type of self-identifying terminology. The problem is when people are perceived to be lying about their identity as a means of getting some sort of advantage. Rachel Dolezal for example was caught lying about her parentage. Trans people generally don't lie to cover their transness (except maybe socially to avoid the attention their transness would garner).

This lying to get an advantage can potentially apply to trans people in sports too. People are always claiming that near elite male athletes who can't win in men's competitions will just say they are women to face easier opponents, but we haven't really seen any evidence of that occurring. This is primarily because the obstacles to check a box on a college application are so drastically different than the obstacles in front of someone who wants to publicly and officially change their gender. Considering that, I think the best approach is to not waste too much energy on "fixing" this problem until it is actually shown to be a problem.

> I couldn't decide to be a Native American without meeting some external criteria around my birth and life.

For the record, people have self-identified as being Black:

* https://www.nbcnews.com/think/opinion/jessica-krug-rachel-do...

* https://www.theguardian.com/us-news/2017/feb/25/rachel-dolez...

* https://en.wikipedia.org/wiki/Rachel_Dolezal

But that's the point. Rachel Dolezal is a grifter and a laughingstock, not a black person.

If anyone can be a woman, then no one is a woman.