+_In all philosophical strictness_, I think I agree. (And I wouldn't want to attend a men-only event.)[ref]But mostly for ideological and gender-dysphoria-related reasons, rather than because I _obviously wouldn't belong_. I've historically been inclined to cultivate a _self-image_ of being "not like the other guys", but self-images [aren't necessarily veridical](/2016/Sep/psychology-is-about-invalidating-peoples-identities/). If my self-perceived unmasculinity isn't reflected in other people's assessments of my unaffected personality and social behavior, it would be somewhat unreflective of me to protest, "But _I'm_ not gender-conforming—I have a _ponytail!_"[/ref] Outside of a few _relatively_ narrow domains of life (medicine, intercourse, family planning), I find it hard to think of good reasons to care about sex _per se_, as opposed to characteristics which might correlate with sex at some nonzero but certainly-not-so-huge-as-to-be-effectively-binary effect size. Ozy and me and Scott Alexander are all in agreement that categories are in the map, not the territory. There aren't ontologically-fundamental <span style="font-family: monospace;"><sex value="F"/></span> XML tags attached to people's souls—and moreover, we wouldn't have any reason to care if there _were_.
+
+The problem is that people don't always _have_ the detailed individual information that they would need to act in all philosophical strictness, at least not in an explicit, communicable form. If you're having a private get-together with some your friends who you know very well, you can pick and choose who to invite based on your individual knowledge of each individual, and you don't need to communicate (much less justify) your decision criteria to anyone else. If you don't like Brian, you can just not-invite-Brian, even if you're bad at introspection and don't even _know for yourself_ why you don't like Brian.
+
+In contrast, imagine telling the organizer of your local Women-in-Your-Favorite-Hobby meetup group, "The actual category you should be using is not _women_ in our-favorite-hobby. The actual category you should be using is, 'people who would contribute to the atmosphere you made this a woman-only event for.'"
+
+"Okay," she says. "So, what should we call the group now?"
+
+You think for a few moments. "What about 'non-exclusively-gynephilic people in our-favorite-hobby who are not less than one standard deviation below the population mean in the Agreeableness and Neuroticism factors of the Big Five personality model'?"
+
+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-gynephilic" 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]
+
+[interruptions study]
+
+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.