+We can't talk about group differences, for fear that anyone arguing that differences exist is just trying to shore up oppression. But ... structural oppression and actual group differences can _both exist at the same time_. They're not contradicting each other! Like, the fact that men are physically stronger than women (on average, but the effect size is enormous, like _d_ ≈ 2.6 for total muscle mass) is _not unrelated_ to the persistence of patriarchy! (The ability to _credibly threaten_ to physically overpower someone, [gives the more powerful party a bargaining advantage](/2020/Jan/book-review-the-origins-of-unfairness/#threatpoints-and-bargaining), even if the threat is typically unrealized.) That doesn't mean patriarchy is good; to think so would be to commit the naturalistic fallacy of [attempting to derive an _ought_ from an _is_](https://plato.stanford.edu/entries/hume-moral/#io). No one would say that famine and plague are good just because they, too, are subject to scientific explanation. This is pretty obvious, really? But similarly, genetically-mediated differences in cognitive repertoires between ancestral populations are probably going to be _part_ of the explanation for _why_ we see the particular forms of inequality and oppression that we do, just as a brute fact of history devoid of any particular moral significance, like how part of the explanation for why European conquest of the Americas happened earlier and went smoother for the invaders than the colonization of Africa had to do with the disease burden going the other way (Native Americans were particularly vulnerable to smallpox, but Europeans were particularly vulnerable to malaria).
+
+Again—obviously—_is_ does not imply _ought_. [TODO: explain that you should imagine yourself in the inferior group]
+
+I don't know how to build a better world, but it seems like there are quite _general_ grounds on which we should expect that it would be helpful to be able to _talk_ about social problems in the language of cause and effect, with the austere objectivity of an engineering discipline. If you want to build a bridge (that will actually stay up), you need to study the ["the careful textbooks \[that\] measure \[...\] the load, the shock, the pressure \[that\] material can bear."](http://www.kiplingsociety.co.uk/poems_strain.htm) If you want to build a just Society (that will actually stay up), you need a discipline of Actual Social Science that can publish textbooks, and to get _that_, you need the ability to _talk_ about basic facts about human existence and make simple logical inferences between them.
+
+And no one can do it! [("Well for us, if even we, even for a moment, can get free our heart, and have our lips unchained—for that which seals them hath been deep-ordained!")](https://www.poetryfoundation.org/poems/43585/the-buried-life) Individual scientists can get results in their respective narrow disciplines; Charles Murray can just _barely_ summarize the science to a semi-popular audience without coming off as _too_ overtly evil to modern egalitarian moral sensibilities. (At least, the smarter egalitarians? Or, maybe I'm just old.) But at least a couple things are even _worse_ (with respect to naïve, non-renormalized egalitarian moral sensibilities) than the ball-hiders like Murray can admit!
+
+Murray approvingly quotes Steven Pinker (a fellow ball-hider, though [Pinker is better at it](https://archive.is/bNo2q)): "Equality is not the empirical claim that all groups of humans are interchangeable; it is the moral principle that individuals should not be judged or constrained by the average properties of their group."
+
+A fine sentiment. I _emphatically_ agree with the _underlying moral intuition_ that makes "Individuals should not be judged by group membership" _sound like_ a correct moral principle—one cries out at the _monstrous injustice_ of the individual being oppressed on the basis of mere stereotypes of what other people who _look_ like them might statistically be like.
+
+But can I take this _literally_ as the _exact_ statement of a moral principle? _Technically?_—no! That's actually not how epistemology works! The proposed principle derives its moral force from the case of complete information: if you _know for a fact_ that I have moral property P, then it would be monstrously unjust to treat me differently just because other people who look like me mostly don't have moral property P. But in the real world, we often—usually—don't _have_ complete information about people, [or even about ourselves](/2016/Sep/psychology-is-about-invalidating-peoples-identities/).
+
+Bayes's theorem (just [a few inferential steps away from the definition of conditional probability itself](https://en.wikipedia.org/wiki/Bayes%27_theorem#Derivation), barely worthy of being called a "theorem") states that for hypothesis H and evidence E, P(H|E) = P(E|H)P(H)/P(E). This is [the fundamental equation](https://www.readthesequences.com/An-Intuitive-Explanation-Of-Bayess-Theorem) [that governs](https://www.readthesequences.com/A-Technical-Explanation-Of-Technical-Explanation) [all thought](https://www.lesswrong.com/posts/QrhAeKBkm2WsdRYao/searching-for-bayes-structure). When you think you see a tree, that's really just your brain computing a high value for the probability of your sensory experiences given the hypothesis that there is a tree multiplied by the prior probability that there is a tree, as a fraction of all the possible worlds that could be generating your sensory experiences.
+
+What goes for seeing trees, goes the same for "treating individuals as individuals": the _process_ of getting to know someone as an individual, involves exploiting the statistical relationships between what you observe, and what you're trying to learn about. If you see someone wearing an Emacs tee-shirt, you're going to assume that they _probably_ use Emacs, and asking them about their [dot-emacs file](https://www.gnu.org/software/emacs/manual/html_node/emacs/Init-File.html) is going to seem like a better casual conversation-starter compared to the base rate of people wearing non-Emacs shirts. Not _with certainty_—maybe they just found the shirt in a thrift store and thought it looked cool—but the shirt _shifts the probabilities_ implied by your decisionmaking.
+
+The problem that Bayesian reasoning poses for naïve egalitarian moral intuitions, is that there's no _philosophically principled_ reason for "probabilistic update about someone's psychology on the evidence that they're wearing an Emacs shirt" to be treated _fundamentally_ differently from "probabilistic update about someone's psychology on the evidence that she's female".
+
+These are of course different questions, but to a Bayesian reasoner (an inhuman mathematical abstraction for _getting the right answer_ and nothing else), they're the same _kind_ of question: the "correct" update to make is an _empirical_ matter that depends on the actual distribution of psychological traits among Emacs-shirt-wearers and among women. (In the possible world where _most_ people wear tee-shirts from the thrift store that looked cool without knowing what they mean, the "Emacs shirt → Emacs user" inference would usually be wrong.) But to a naïve egalitarian, judging someone on their expressed affinity for Emacs is good, but judging someone on their sex is _bad and wrong_.
+
+I used to be a naïve egalitarian. I was very passionate about it. I was eighteen years old. I am—again—still fond of the moral sentiment, and eager to renormalize it into something that makes sense. (Some egalitarian anxieties do translate perfectly well into the Bayesian setting, as I'll explain in a moment.) But the abject horror I felt at eighteen at the mere suggestion of _making generalizations_ about _people_ just—doesn't make sense. Not that it _shouldn't_ be practiced (it's not that my heart wasn't in the right place), but that it _can't_ be practiced—that the people who think they're practicing it are just confused about how their own minds work.
+
+Give people photographs of various women and men and ask them to judge how tall the people in the photos are, as [Nelson _et al._ 1990 did](/papers/nelson_et_al-everyday_base_rates_sex_stereotypes_potent_and_resilient.pdf), and people's guesses reflect both the photo-subjects' actual heights, but also (to a lesser degree) their sex. Unless you expect people to be perfect at assessing height from photographs (when they don't know how far away the cameraperson was standing, aren't ["trigonometrically omniscient"](https://plato.stanford.edu/entries/logic-epistemic/#LogiOmni), _&c._), this behavior is just _correct_: men really are taller than women on average (I've seen _d_ ≈ 1.4–1.7 depending on the source), so P(true-height|apparent-height, sex) ≠ P(height|apparent-height) because of [regression to the mean](https://en.wikipedia.org/wiki/Regression_toward_the_mean) (and women and men regress to different means).
+
+But this all happens subconsciously—and people _can't turn it off_. In the same study, when the authors tried height-matching the photographs (for every photo of a woman of a given height, there was another photo in the set of a man of the same height) _and telling_ the participants about the height-matching _and_ offering a cash reward to the best height-judge, more than half of the stereotyping effect remained. It would seem that people can't consciously readjust their learned priors in reaction to verbal instructions pertaining to an artificial context.
+
+The point is, once you understand at a _technical_ level that probabilistic reasoning about demographic features is both epistemically justified, _and_ implicitly implemented as part of the way your brain processes information _anyway_, then a moral theory that forbids this starts to look much less compelling. Maybe a Bayesian superintelligence could redesign the human brain to _not_ use Bayesian reasoning when contemporary egalitarians would find that ideologically disagreeable? But a world populated by such people, constitutionally incapable of reacting to statistical regularities that we, in our world, automatically take into account (without necessarily noticing that we do), would likely come off as creepy or uncanny.
+
+[TODO: elaborate on a specific uncanniness]
+
+[TODO: really need to address "But choice!" or "But not for psychology!" objections]
+
+Of course, statistical discrimination on demographic features is only epistemically justified to exactly the extent that it helps _get the right answer_. Renormalized-egalitarians can still be unhappy about the monstrous tragedies where I have moral property P but I _can't prove it to you_, so you instead guess _incorrectly_ that I don't just because other people who look like me mostly don't, and you don't have any better information to go on. Nelson _et al._ also found that when the people in the photographs were pictured sitting down, then judgements of height depended much more on sex than when the photo-subjects were standing. This also makes Bayesian sense:
+
+["more likelihood ratios is a _different_ moral than "don't descriminate"]
+
+[the other thing the ball-hiders can't get right: actually, IQ is morally valuable]