Deliberately Vague Language is Bullshit

I don't entirely agree. I think vague language is sometimes bullshit but sometimes honesty.

I am a human being rather than an idealized superintelligence. Sometimes my own knowledge and understanding are vague. E.g., to take one of the examples in the OP, I may say "you probably shouldn't try for a career in theoretical physics unless you are very smart"; I'm not giving an "IQ threshold" (or a mapping from IQ to probability of success, or whatever) because I don't have one to give. I could be more concrete: "you probably shouldn't try for a career in theoretical physics unless you have an IQ of at least 130" or something. But that would likely be interpreted as meaning that I have a detailed understanding of the relationship between the cognitive requirements of a theoretical physics career and the things measured by IQ tests, and that I've somehow found that 130 is the Right Threshold, and none of that is true. I could be more concrete and make the hedging explicit: "theoretical physics requires a lot of very hard thinking, the sort that correlates well with IQ test results. I have very little idea what the exact requirements are but a super-handwavy guess is that if your IQ isn't at least 130 and you don't have concrete evidence that you're better at theoretical physics than your IQ would suggest, you probably won't have a good time trying to be a theoretical physicist". But brevity has value, and frankly that much longer version doesn't actually convey much more information than "you need to be very smart".

Unless you and your interlocutor are completely indifferent to the downsides of verbosity, when your knowledge is vague your language should sometimes also be vague.

Vague language is often the result of vague thinking; most people do not actually try to be specific in their thinking; many of them don't know how.

Vague language will also arise when language doesn't correctly encapsulate a concept, or when the writer doesn't know how to use language for that specific purpose; pointing more specifically at the wrong thing is being actively misleading.  Thus vague language can often occur in areas where there isn't a common and codified way of expressing specific thoughts.  For example, this post is vague about what vague language is; the specific concept is one I suspect you've never had to specify, so it's hard to translate it into words.  Instead you focus on what it isn't, trying to be specific by ruling out, rather than ruling in.

Vague language can also arise in areas where the common communication mechanism is necessarily lossy, such as when talking about qualia.

I think "deliberate" is doing most of the heavy lifting in this post.

"Fit" is vaguer than BMI and bodyfat percentage. 

While I agree that it's more vague I don't think using a word like fit always suggest bullshit. Someone with strong asthma and reduced lung function might have a BMI and bodyfat percentage that otherwise correspond to being fit but they still aren't fit according to the common meaning of fit. 

There are goodhearting interventions such as fat removal that clearly help with BMI and bodyfat while increasing the average size of fat cells which happens to be bad and makes people less fit. 

If you find yourself or others using deliberately vague language around a topic it means there is something you can't say.

The same goes for only allowing precise language. If you only allow precise language you prevent people from pointing to goals like being fit that they don't know how to operationalize well. This leads to metrics that then get goodharted without leading to what the person who wants to be fit actually wants. 

This is pointing in a good direction, but I think the post could benefit from some more concrete examples.

A Paul Graham essay which is more directly related to this topic is How to Write Usefully:

Useful writing makes claims that are as strong as they can be made without becoming false.

For example, it's more useful to say that Pike's Peak is near the middle of Colorado than merely somewhere in Colorado. But if I say it's in the exact middle of Colorado, I've now gone too far, because it's a bit east of the middle.

Precision and correctness are like opposing forces. It's easy to satisfy one if you ignore the other. The converse of vaporous academic writing is the bold, but false, rhetoric of demagogues. Useful writing is bold, but true.

There are a lot of cases where vague language is all you have. There is no way to be more precise. And if you are aware of that you will be deliberate about it. Thus I am unhappy with your choice. I think more accurate would have been to call it misleadingly vague langue - which makes it kind of trite/trivial.

In case it's not clear what I mean by vague language by need here are some examples:

• You just don't know enough of the subject (yet). Being deliberate about it might mean that you are honest about that.
• The audience is not familiar enough with the subject and the precise terminology. While I think this may be true in some circumstances I wouldn't say it's usually true with the media.
• There is not enough precise terminology and knowledge about the subject at all. This is the case with all new knowledge at the beginning - sometimes even physics and math. It is toying around with ideas and analogies and seeing what sticks and works. This is the state still with quite a lot of the soft sciences. And that is OK. It is how over time we move from imprecise to precise definitions. Look at a lot of what Scott Alexander writes. While clearly, he tries to use as precise terms as he can a typical m.o. is to approach the topic from multiple sides and use multiple analogies and examples.   

"Fit" is vaguer than BMI...

Which is in every way less precise and useful than body shape index (ABSI). BMI fails for: athletes and strong people, people over 50, smokers and ex-smokers, skinny-fat people; in fact it fails for most people. Maximum longevity is in the (mildly) overweight category of BMI.

ABSI predicts heart disease mortality far better than blood tests. BMI is not even in the race except at extremes.

This is a classic case of medicine's common practice of  persisting with inferior metrics and practices. My suspicion is that this is a result of the excessive power of "great men" and authorities within the field. 

See refs at the end of this https://www.fatcalc.com/absi

Vague language (and low communication more generally) also gives you plausible deniability for bending the truth.

Related: It's a common feature of Machiavellianism to "keep one's cards hidden" (12:25 here), i.e., not disclosing motives behind one's actions and generally communicating little information. 

People without anything to hide can build trust by communicating a lot and clearly.

The post is about being specific [LW · GW], precision in communication, not truth. In practice, truth is given by evident hypotheses, those readily verifiable or otherwise supported by available evidence. Getting to that point benefits from precise communication of concepts and hypotheses, building blocks of truth judgements (as well as claims about how to attain relevant evidence), but communication doesn't itself convey their truth. Conflating these different ideas wastes opportunity for precision.

I think true, but kind of trivial.  The vast majority of human interaction is bullshit (very often bullshit mixed with a small amount of metaphorical or directional actual communication (meaning: true and surprising data that someone can update on)).  Of course this includes vagueness, and especially vagueness that doesn't include an explanation of WHY it's unspecific.  

It's the reason LW reacts so badly to generalizations of politics as a weak attempt to discuss politics without the mind-killing.

See also: The trouble with passive voice sentences [LW · GW].

If numbers could be used but aren't then you are dealing with a taboo subject

Alternatively, the speaker doesn't precisely know, or the specifics are a distinction without consequence.  E.g., gjm's example where someone recommends against pursuing a career in theoretical physics "unless you're very smart."

Vague language is bullshit when the vagueness is deliberate with the intention to mislead.

Maybe this could be a subset of "simple" language  (vague because complexity is unnecessary), but it's not clear if this was an intent of that category.

I have not yet read the book, but from a recommendation I infer that Leo Strauss' "Persecution and the Art of Writing" goes into considerable depth on the mechanics of using vagueness as a dogwhistling mechanism.

I generally agree with the post but I miss a paragraph pointing at that precise language can be (and it is extensively used to) bullshit. It is hinted in "How many shares of a company you own is vaguer than what percentage you own". And also, as others say, vague language does not imply attempting to obscure reality.

I find also that nuanced language is much more precise and less bullshit than very direct language.

Bullshit is what comes out of the mouth of someone who values persuasion over truth. [...] The people with a need to obscure the truth are those with a political or social agenda.

Almost all humans, in almost all contexts, value persuasion over truth and have a social agenda. Condemning all human behavior that is not truth-seeking is condemning almost all human behavior. This is a strong (normative? prescriptive? judgmental?) claim that should be motivated, but you seem to take it for given.

Persuasion is a natural and desirable behavior in a social, cooperative species that is also competitive on the individual level. The main alternative to persuasion is force, and in most cases I'm glad people use persuasion rather than force. Truth-seeking would also fare worse in a more violent world, because truth has some persuasion value but little violence-value.

Truth is instrumentally useful to persuasion inasfar as people are able to identify truth and inclined to prefer it. I'm all for increasing these two characteristics and otherwise "raising the sanity waterline". But that is very far from a blanket condemnation of "valuing persuasion over truth".

"Bullshit is what Bullshitters use to justify their Bullshit to other Bullshitters."

( Vaguely motioning to a vague meme-like chart vaguely referring to some vague graphical Bullshit about some vague bullshit.) 

But it's broadly applicable and will only offend people you don't like. 

(Vaguely motioning to a different vague meme-like chart vaguely referring to some bullshit about the new bullshit.) 

It's funny that you mention this as I stumbled across this classic bit from the Onion just the other day and was looking for a good excuse to share it. (Warning: more coarse language)