Almost all instances of the word "true" can be eliminated from the sentences in which they appear by applying Tarski's formula. For example, if you say, "I believe the sky is blue, and that's true!" then this can be rephrased as the statement, "I believe the sky is blue, and the sky is blue." For every "The sentence 'X' is true" you can just say X and convey the same information about what you believe - just talk about the territory the map allegedly corresponds to, instead of talking about the map.
When can't you eliminate the word "true"? When you're generalizing over map-territory correspondences, e.g., "True theories are more likely to make correct experimental predictions." There's no way to take the word 'true' out of that sentence because it's talking about a feature of map-territory correspondences in general.
Similarly, you can eliminate the sentence 'rational' from almost any sentence in which it appears. "It's rational to believe the sky is blue", "It's true that the sky is blue", and "The sky is blue", all convey exactly the same information about what color you think the sky is - no more, no less.
When can't you eliminate the word "rational" from a sentence?
When you're generalizing over cognitive algorithms for producing map-territory correspondences (epistemic rationality) or steering the future where you want it to go (instrumental rationality). So while you can eliminate the word 'rational' from "It's rational to believe the sky is blue", you can't eliminate the concept 'rational' from the sentence "It's epistemically rational to increase belief in hypotheses that make successful experimental predictions." You can Taboo the word, of course, but then the sentence just becomes, "To increase map-territory correspondences, follow the cognitive algorithm of increasing belief in hypotheses that make successful experimental predictions." You can eliminate the word, but you can't eliminate the concept without changing the meaning of the sentence, because the primary subject of discussion is, in fact, general cognitive algorithms with the property of producing map-territory correspondences.
The word 'rational' should never be used on any occasion except when it is necessary, i.e., when we are discussing cognitive algorithms as algorithms.
If you want to talk about how to buy a great car by applying rationality, but you're primarily talking about the car rather than considering the question of which cognitive algorithms are best, then title your post Optimal Car-Buying, not Rational Car-Buying.
Thank you for observing all safety precautions.
I come to Less Wrong to learn about how to think and how to act effectively. I care about general algorithms that are useful for many problems, like "Hold off on proposing solutions" or "Habits are ingrained faster when you pay concious attention to your thoughts when you perform the action". These posts have very high value to me because they improve my effectiveness across a wide range of areas.
Another such technique is "Dissolving the question". The post you linked to (Yvain's "Diseased thinking: dissolving questions about disease") is valuable as an exemplary performance of this technique. It adds to Eliezer's description of question-dissolving by giving a demonstration of its use on a real question. It's main value comes from this, anything I learnt about disease whilst reading it is just a bonus.
To quote badger in the recent thread "Rational Toothpaste: A Case Study"
But we don't need more than one or two such examples! Yvain's post about question-dissolving was the only such post I ever need to read.
Posts about toothpaste or house-buying or room-decoration or fashion (EDIT: shaving, computer hardware) only tell me about that particular thing. As good as many of them are they'll never be as useful as a post that teaches me a general method of thought applicable on many problems. And if I want to know about some particular topic I'll just look it up on Google, or go to a library.
It's not possible for LessWrong to give a rational treatment of every subject. There are just too many of them. Even if we did I wouldn't be able to carry all that info around in my head. That's why I need to learn general algorithms for producing rational decisions.
(Also: Even though badger makes it clear in the quote I gave that the post is supposed to about the algorithms used, only one of the comments on it (kilobug's) is talking about this. Most of the rest are actually talking about toothpaste.)
EDIT: Should I repost this to discussion level?
Yes.