+> I've seen one anti-transgender argument around that I take very seriously. The argument goes: we are rationalists. Our entire shtick is trying to believe what's actually true, not on what we wish were true, or what our culture tells us is true, or what it's popular to say is true. If a man thinks he's a woman, then we might (empathetically) wish he were a woman, other people might demand we call him a woman, and we might be much more popular if we say he's a woman. But if we're going to be rationalists who focus on believing what's actually true, then we've got to call him a man and take the consequences.
+>
+> Thus Abraham Lincoln's famous riddle: "If you call a tail a leg, how many legs does a dog have?" And the answer: "Four—because a tail isn't a leg regardless of what you call it."
+>
+> [...]
+>
+> I take this argument very seriously, because sticking to the truth really is important. But having taken it seriously, I think it's seriously wrong.
+>
+> An alternative categorization system is not an error, and borders are not objectively true or false.
+
+But this is just giving up _way_ too easily. The map is not the territory, and many very different kinds of maps can correspond to the territory in different ways—we have geographical maps, political maps, road maps, globes, _&c._—but that doesn't mean _no map is in error_. Rationalists can't insist on using the one true categorization system, because it turns out that—in all philosophical strictness—no such thing exists. But that doesn't release us from our sacred duty to describe what's actually true. It just leaves us faced with the _slightly more complicated_ task of describing the costs and benefits of different categorization systems with respect to different criteria.
+
+There's no objective answer to the question as to whether we should pay more attention to an animal's evolutionary history or its habitat—but given one criterion or the other, we can say definitively that whales _are_ mammals but they're also _dag_/water-dwellers. And this isn't just a matter of [mere labels](http://lesswrong.com/lw/ns/empty_labels/) that contain no more information than we used to define them. The categories do cognitive work: given that we observe that whales are endotherms that nurse their live-born young, we can assign them to the category _mammal_ and predict—correctly—that they have hair and have a more recent last common ancestor with monkeys than with herring, even if we haven't yet seen the hairs or found the last common ancestor. Alternatively, given that we've been told that "whales" live in the ocean, we can assign them to the category _water-dwellers_, and predict—correctly—that they're likely to have fins or flippers, even if we've never actually seen a whale ourselves.
+
+This works because, empirically, mammals have lots of things in commmon with each other and water-dwellers have lots of things in common with each other. If we [imagine entities as existing in a high-dimensional configuration space](http://lesswrong.com/lw/nl/the_cluster_structure_of_thingspace/), there would be a _mammals_ cluster (in the subspace of the dimensions that mammals are similar on), and a _water-dwellers_ cluster (in the subspace of the dimensions that water-dwellers are similar on), and whales would happen to belong to _both_ of them, in the way that the vector *x⃗* = [3.1, 4.2, −10.3, −9.1] ∈ ℝ⁴ is close to [3, 4, 2, 3] in the _x₁-x₂_ plane, but also close to [−8, −9, −10, −9] in the _x₃-x₄_ plane.
+
+If different political factions are engaged in conflict over how to define the extension of some common word—common words being a scarce and valuable resource both culturally and [information-theoretically](http://lesswrong.com/lw/o1/entropy_and_short_codes/)—rationalists may not be able to say that one side is simply right and the other is simply wrong, but we can at least strive for objectivity in _describing the conflict_. Before shrugging and saying, "Well, this is a difference in values; nothing more to be said about it," we can talk about the detailed consequences of what is gained or lost by paying attention to some differences and ignoring others. That there exists an element of subjectivity in what you choose to pay attention to, doesn't negate the fact that there _is_ a structured empirical reality to be described—and not all descriptions of it are equally compact.
+
+In terms of the Lincoln riddle: you _can_ call a tail a leg, but you can't stop people from _noticing_ that out of a dog's five legs, one of them is different from the others. You can't stop people from inferring decision-relevant implications from what they notice. (_Most_ of a dog's legs touch the ground, such that you'd have to carry the dog to the vet if one of them got injured, but the dog can still walk without the other, different leg.) And if people who work and live with dogs every day find themselves habitually distinguishing between the bottom-walking-legs and the back-wagging-leg, they _just might_ want _different words_ in order to concisely _talk_ about what everyone is thinking _anyway_.
+
+-----
+
+So far, I probably haven't actually said anything that Alexander didn't already say in the original post. ("A category 'fish' containing herring, dragonflies, and asteroids is going to be stupid [...] it fails to fulfill any conceivable goals of the person designing it.") But it seems worth restating and emphasizing that categories derive their usefulness from the way in which they efficiently represent regularities in the real world, because on the topic of exactly how to apply these philosophical insights to transgender identity claims, Alexander strangely—uncharacteristically—doesn't seem to find it necessary to make any arguments about representing the real world, preferring instead to focus on the mere fact that some people strongly prefer [self-identity](/2016/Sep/psychology-is-about-invalidating-peoples-identities)-based gender categories:
+
+> If I'm willing to accept an unexpected chunk of Turkey deep inside Syrian territory to honor some random dead guy—and I better, or else a platoon of Turkish special forces will want to have a word with me—then I ought to accept an unexpected man or two deep inside the conceptual boundaries of what would normally be considered female if it'll save someone's life. There's no rule of rationality saying that I shouldn't, and there are plenty of rules of human decency saying that I should.
+
+This is true in a tautological sense: if you deliberately gerrymander your category boundaries in order to get the answer you want, you can get the answer you want, which is great for people who want that answer, and people who don't want to hurt their feelings [(and who don't mind letting themselves get emotionally blackmailed)](/2017/Jan/dont-negotiate-with-terrorist-memeplexes/).
+
+But it's not very interesting to people like rationalists—although apparently not all people who _self-identify_ as rationalists—who want to use concepts to _describe reality_.
+
+-----