Rationality requires intelligence, and the kind of intelligence that we use (for communication, progress, FAI, etc.) runs on language.
It seems that the place we should start is optimizing language for intelligence and rationality. One of SIAI's proposals includes using Lojban to interface between humans and an FAI. And of course, I should hope the programming language used to build a FAI would be "rational". But it would seem to me that the human-generated priors, correct epistemic rationality, decision theory, metaethics, etc. all depend on using a language that sufficiently rigorously maps to our territory.
Are "naturally evolved" languages such as English sufficient, with EY-style taboos and neologisms? Or are they sick to the core?
Please forgive and point me towards previous discussion or sequences about this topic.
No, I don't. Evolution is always a hack of what came before it, whereas scrapping the whole thing and starting from scratch doesn't suffer from that problem. I don't need to hack an existing structure; I can build exactly what I want right now.
Here's an excellent example of this general point: Self-segregating morphology. That's the language construction term for a sound system where the divisions between all the components (sentences, prefixes, roots, suffixes, and so on) are immediately obvious and unambiguous. Without understanding anything about the speech, you know the syntactical structure.
That's a pretty cool feature, right? It's easy to build that into an artificial language, and it certainly makes everything easier. It would be an important part of having a stable sound system. The words wouldn't interfere with each other, because they would be unambiguously started and terminated within a sound system where the end of every word can run smoothly against the start of any other word. If I were trying to make a stable sound system, the first thing that I would do is make the morphology self-segregating.
But if a self-segregating morphology is such a happy point, why hasn't any natural language come to that point? Well, that should be pretty obvious. No hack could transform a whole language into a having a self-segregating morphology. Or at least I don't know of such a hack. But even then, it's trivially easy to make one if you start from scratch! Don't you accept the idea that some things are easier to design than evolve (because perhaps the hacking process doesn't have an obvious way to be useful throughout every step to get to the specific endpoint)?
That whole mountain of evidence concerns natural languages with irregular sound systems. A self-segregating morphology that flows super well would be a whole different animal.
Per my points above, I still don't see why using the capabilities of the natural language hardware would lead to it changing in all sorts of unpredictable ways, especially if it's not used for anything but trying to reproduce your thought in their head, and if it's not used by anybody but a specific group of people with a specific purpose in mind. I still imagine an engine well-built to drive its own evolution in a useful way, and avoid becoming an irregular mess.
How do you know that? To support this claim, you need a model that predicts the actually occurring sound changes in natural languages, and also that sound changes would not occur in a language with self-segregating morphology. Do you have such a model? If you do, I'd be tremendously curious to see it.