Words, and "Rationality"
Some of this discussion is fraught, unfortunately, because of the bombast that the word "rationality" evokes. It's useful here to say some about what I think words are and aren't.
Mostly I would say, words are just that: despite the authoritativeness that the use of a word can have, words are "in fact" symbols which carry culturally constituted meaning, etc etc. This is to say, just because we have a word for something, or we're used to thinking about there being this or that category, that's in principle only necessarily a fact about the way humans see the world, and how that's reflected in our cultures and languages. Words can also refer to things which don't exist, or which group together many different things that actually have very little in common.
We can also define words narrowly in a particular context, and understand the word to refer to that definition in that context. Obviously, of course, there is still connotation, and a lot of abuse can be done by implicitly bringing in intuitions about some word or category, while [insisting that one is only using a very specific definnition].
The illusion of transparency
[ something something just using a word and the other person seeming to affirm that they understand you is not that strong of evidence that you're actually communicating this isn't narrowly about words but still idk how to say this more legibly, but like so there's two things, one being like, you have to serialize and deserialize, using ontologies that are potentially askew, especially for things that are at the edge of either of your sensemaking etc and there's a sort of human social thing where people often are socialized into producing the right noises and facial expressions as though they're communicating, because appearing not to communicate is awkward, maybe even rude etc. so people will affirm that they understand you when they just don't!
but more seriously, often both sides aren't even bullshitting, and actually think they're communicating, but they're using different ontologies or just have different priors and then they're hardly communicating at all
[also re translation, etymology, connotation etc. it's often opaque what a translation means, and when we say "x in other language means y in my language" we have to assume that they have narrowly the same ontology often ontological impedance mismatches are kind of subtle but also not that important, like, exactly where do the legs end at the buttocks start? where does the waist start? mostly who cares, from the perspective of translation, but this gets way harder when we're translating spiritual materials from other languages.] ]
"""Rationality"""
With respect to "rationality" in particular, one would be reasonable to complain: "who are you to say that you own or can define truth, at everyone else's expense?" I think this is basically a good take, and insofar as I fall into speaking singularly authoritatively about "rationality," I'm mostly just being sloppy. However, I still think there's a very important collection of concepts which I need to make reference to... and it would only confuse matters to try to come up with a new name for them. Probably a productive angle from which to engage here would be to say, "ok, this is a fine enough concept, agnostic of the name," and notice what distinctions it makes salient.
Also unfortunately, a number of intellectual movements have used the word 'rational' or 'rationality.' I'm pretty thinly read here, and mostly pulling from Yudkowsky, but I believe the definitions below originally come from a literature on rationality in the 20th century, by way of decision theory, economics, and psychology, starting with Von Neumann and Morgenstern.
One last point: "rational" often evokes what Yudkowsky calls a "straw vulkan" —a caricatured person with no emotion, who only thinks in probabilities, weights, and causality. I think this image is less of a strawman than would be flattering, but I'll stress that rationality, as I approach it and as Yudkowsky presents it, is not fundamentally in contradiction to human richness and sensitivity.