+I can think of a few criticisms of this proposal.
+
+First of all, there's a lot of room for disagreement over the operationalization of "people who would contribute to the atmosphere you made this a woman-only event for" in terms of some function of individual psychological traits that would exclude some women and include some men.
+
+I, the author of this blog post, went with "not-exclusively-androphilic" because I'm imagining that part of the appeal of women-only spaces is not having to deal with people who might want to hit on you, but that excluding bisexual women would go too far; and I went with "more than −1σ in Agreeableness and Neuroticism" because the Big Five seems to be the most popular personality model in the study of psychology, and Agreeableness and Neuroticism are the dimensions of that model with the largest sex differences, at _d_≈0.5 and _d_≈0.4, respectively[ref][Weisberg _et al_](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3149680/)[/ref].
+
+[TODO: footnote calculation of how many women and men this would exclude]
+
+[TODO: address that "non-exclusively-androphilic" does exclude lesbians]
+
+But that was just my _guess_ at how to apply reductionism to describe the atmosphere of women-only spaces using lower-level criteria—and it was probably a _bad_ guess. (For one thing, [TODO: lesbians]) A woman who benefits from women-only spaces and knows more about psychology than me might say something different, and we should listen to _her_, not me. The "more than −1σ in both of these two dimensions" threshold was completely arbitrary; maybe she would prefer some other function. Maybe she [doesn't like the Big Five model](https://en.wikipedia.org/w/index.php?title=Big_Five_personality_traits&oldid=868909816#Critique). Maybe (in fact, almost certainly) multiple such women wouldn't _agree_ on the exact criteria.
+
+But even if such a committee of female psychologists _could_ agree on such criteria, I think most people would say that reorganizing the group as the "not-exclusively-androphilic people in our-favorite-hobby whose results on this-and-such personality battery match the following 1 KiB description ..." does not seem very appealing.
+
+It would seem that in a world where psychological traits can't be cheaply, precisely, and verifiably measured, discrimination on the basis of [easily-observable traits that happen correlate with harder-to-measure traits that we actually care about](/2018/Feb/blegg-mode/) turns out to be a practical bright-line Schelling point for people to coordinate around.
+
+_Not_ an infinitely-thin, infinitely-bright line,[ref]As it is said: what about masculine women and feminine men (whose share of the population depends on where you set your sex-atypicality thresholds)? What about trans people (0.3%–[TODO] of the population, depending on how you define your categories and whose statistics you trust)? What about people with [5α-Reductase deficiency](https://en.wikipedia.org/wiki/5%CE%B1-Reductase_deficiency) or any of a dozen other specific intersex conditions?[/ref] but a line thin _enough_ and bright _enough_ that the forces of social evolution have coughed up some institutions and other cultural practices that take the line into account for _functional_ reasons.
+
+My goal in writing about this is certainly not to argue for _more sexism_—I'm looking forward to the postgender lesbian transhumanist future of Total Morphological Freedom as much as anyone else. (I already have my new name and outfits picked out!) If we can invent _new_ institutions and practices that serve more people more effectively, we should _do it_. But because I am a rationalist, because I cannot _unsee_ the cold, oppressive logic of [Chesterson's fence](https://en.wikipedia.org/wiki/Wikipedia:Chesterton's_fence), I have to speak when my friends resort to using facile, sophmoric word games [TODO: soften!] to obfuscate the _function_ of the existing fences.
+
+In response to the argument that women's restrooms function as safe havens away from scary men [TODO: verify paraphrase], Ozy writes:
+
+> I do not understand the relationship between this and psychological gender differences. It seems quite obvious that the relevant category here is "people who look like the vast majority of street harassers" versus "people who do not look like the vast majority of street harassers." The former group uncontroversially includes some trans women (closeted trans women) and some trans men (Buck Angel) and has nothing to do with psychology anyway. No matter how female-typical a trans man’s psychology is, if he has muscles like Chris Hemsworth and a beard like a lumberjack, he belongs in the men's room.
+
+It has to do with _probabilistic perceptions_ of psychology.