+At least, a _pedagogy_ mistake. If Yudkowsky _just_ wanted to make a politically neutral technical point about the difference between fact-claims and policy claims _without_ "picking a side" in the broader cultural war dispute, these Tweets did a very poor job of it. I of course agree that pronoun usage conventions, and conventions about who uses what bathroom, are not, themselves, factual assertions about sex chromosomes in particular. I'm not saying that Yudkowsky made a false statement there. Rather, I'm saying that it's _bizarre_ to condescendingly point this out _as if it were the crux of contemporary trans-rights debates_. Conservatives and gender-critical feminists _know_ that trans-rights advocates aren't falsely claiming that trans women have XX chromosomes. But the question of what categories epistemically "carve reality at the joints", is _not unrelated_ to the question of which categories to use in policy decisions: the _function_ of sex-segrated bathrooms is to protect females from males, where "females" and "males" are natural clusters in configuration space that it makes sense to want words to refer to.
+
+Even if the thread only explicitly mentioned pronouns and not the noun "woman", in practice, and in the context of elite intellectual American culture in which "trans women are women" is dogma, I don't see any _meaningful_ difference between "you're not standing in defense of truth if you insist on a word, brought explicitly into question, being used with some particular meaning" and "I can define the word 'woman' any way I want." (About which, the Yudkowsky of 2008 had some harsh things to say, as excerpted above.) It's hard to read the Tweets Yudkowsky published as anything other than an attempt to intimidate and delegitimize people who want to use language to reason about sex rather than gender identity. [For example](https://twitter.com/ESYudkowsky/status/1067490362225156096), deeper in the thread, Yudkowsky wrote:
+
+> The more technology advances, the further we can move people towards where they say they want to be in sexspace. Having said this we've said all the facts. Who competes in sports segregated around an Aristotelian binary is a policy question (that I personally find very humorous).
+
+Sure, _in the limit of arbitrarily advanced technology_, everyone could be exactly where they wanted to be in sexpsace. Having said this, we have _not_ said all the facts relevant to decisionmaking in our world, where _we do not have arbitrarily advanced technology_. As Yudkowsky [acknowledges in the previous Tweet](https://twitter.com/ESYudkowsky/status/1067488844122021888), "Hormone therapy changes some things and leaves others constant." The existence of HRT does not take us into the Glorious Transhumanist Future where everyone is the sex they say they are.
+
+Rather, previously sexspace had two main clusters (normal females and males) plus an assortment of tiny clusters corresponding to various [disorders of sex development](https://en.wikipedia.org/wiki/Disorders_of_sex_development), and now it has two additional tiny clusters: females-on-masculinizing-HRT and males-on-feminizing-HRT. Certainly, there are situations where you would want to use "gender" categories that use the grouping {females, males-on-feminizing-HRT} and {males, females-on-masculinizing-HRT}.
+
+But the _reason_ for having sex-segregated sports leagues is because the sport-relevant multivariate trait distributions of female bodies and male bodies are quite different.
+
+[TODO: relevance of multivariate—
+
+Different traits have different relevance to different sports; the fact that it's apples-to-oranges is _why_ women do better in ultraswimming—that competition is sampling a corner of sportspace where body fat is an advantage
+
+It's not that females and males are exactly the same except males are 10% stronger on average
+
+It really is an apples-to-oranges comparison, rather than "two populations of apples with different mean weight"
+
+https://www.lesswrong.com/posts/cu7YY7WdgJBs3DpmJ/the-univariate-fallacy
+https://www.lesswrong.com/posts/vhp2sW6iBhNJwqcwP/blood-is-thicker-than-water
+
+If you just had one integrated league, females wouldn't be competitive (in almost all sports, with some exceptions [like ultra-distance swimming](https://www.swimmingworldmagazine.com/news/why-women-have-beaten-men-in-marathon-swimming/)).
+]
+
+[TODO: sentences about studies showing that HRT doesn't erase male advantage
+https://twitter.com/FondOfBeetles/status/1368176581965930501
+https://link.springer.com/article/10.1007/s40279-020-01389-3
+https://bjsm.bmj.com/content/55/15/865
+]