Having a better language helps. Every language has some pain points that are responsible for more than their fair share of miscommunications. Just to use English as an example, although this is true of most natural languages, the overuse of the copula "is/are" is a consistent source of mistakes whether accidental or purposeful. So much so that computer programmers learning object oriented programming have to be taught the difference between "is-a" vs "has-a" relationships.
If you say "My coworker Taro is a samurai", what does that mean? Did he dress up as a samurai for the office costume party? Does he study older forms of Japanese martial arts? Was he descended from a noble family from the Japanese feudal era and have claim to an actual samurai title?
There are controlled dialects of English, like E-Prime, which forbid the use of the copula "to be" as ungrammatical, or at least heavily restrict it. You can say your coworker "dressed as a samurai", "trains in the arts of a samurai", or "traces ancestral lineage from a samurai clan", but you can't say he "is a samurai" in E-Prime.
Would this make communication more clear with fewer mistakes? I don't think this has been adequately studied enough to say for certain. But at least in certain domains like military speech and air traffic control we have examples of such enforced language simplification resulting in measurable decreases in miscommunications. I'm very curious to see if we can generalize those results to a full, general-purpose dialect or entirely new language.
> the overuse of the copula "is/are" is a consistent source of mistakes whether accidental or purposeful
I’m not sure I’d characterise these as ‘mistakes’, per se. They’re just a consequence of the fact that the copula is multifunctional — just like every other English word. In fact, you could similarly criticise almost any common word: ‘go’, ‘from’, ‘good’, ‘like’, ‘not’…
But no, "is/are" is not multifunctional in the same way that "from" is. If I say "she came from school" it is clear that we're talking about relative motion today or in the recent past from one nearby location to another. If I say "her family came from Japan" it is clear I'm talking about ancestry and/or a long ago emigration, but also spatially oriented. If I say "the party is from 3pm to 5pm" then I am using "from" to indicate a temporal rather than a spatial motion. But it still conveys the same basic meaning in all these cases, as the origin point of a motion or interval, and it is not usually the case that a single usage of the word could be confused for more than one meaning.
The IS-A vs HAS-A relationship is entirely different. It is the difference between existential quantification (some aspect of this thing resembles/has an X) and universal quantification (the entirety of this thing is fully captured by the meaning of X). Rigorously analyzed these are very different claims. In a strongly typed language they couldn't be substituted for each other.
To make this concrete, if I say "he is bad" then it is unclear whether I am saying that person is an intrinsically bad man, or if I am just commenting that the thing that he is doing right now is not morally justified.
This may seem like splitting hairs, but that's rather the point. It's at the edge of what we are comfortable thinking about in everyday life. But how much of that is because the language that we use--English--doesn't have these distinctions built into its very foundation? If we were native speakers of a E-Prime, maybe this distinction would be obvious and trivial. And maybe, just maybe, we wouldn't let politicians and con men off the hook so easily for equivocating language.
‘The copula can be used in many different situations.’
-----
Also, I think you underestimate the amount of variation in other words, e.g.:
> If I say "she came from school" it is clear that we're talking about relative motion today or in the recent past from one nearby location to another.
Not just recent past, but having any time near to the point of reference: ‘When she came from school after the bomb scare…’.
> If I say "her family came from Japan" it is clear I'm talking about ancestry and/or a long ago emigration, but also spatially oriented.
Or they might have arrived yesterday to visit her.
> If I say "the party is from 3pm to 5pm" then I am using "from" to indicate a temporal rather than a spatial motion.
But only because ‘3pm’ and ‘5pm’ themselves have clear temporal reference as opposed to spatial reference. For an ambiguous example, if I say ‘we drove from breakfast to lunch’, that might mean we drove starting at breakfast-time and finishing at lunch-time, or it might mean we started at a location where we had breakfast and drove to a location where we had lunch. (To more fully show that the latter is a valid interpretation, consider ‘we drove from breakfast to breakfast’: it makes no sense if ‘breakfast’ is a time, but it makes sense if treated with the sense of ‘place where we had breakfast’.)
-----
> The IS-A vs HAS-A relationship is entirely different. It is the difference between existential quantification (some aspect of this thing resembles/has an X) and universal quantification (the entirety of this thing is fully captured by the meaning of X).
This doesn’t sound quite right to me. In my view, both ‘has’ and ‘is’ are basically relationships, rather than quantifiers. Consider a sentence like ‘I have the keys’: this merely states a relationship between two objects, rather than quantifying over any set. A sentence like ‘The morning star is the evening star’ is similar in this regard. It is true that a sentence like ‘I have a key’ has existential meaning — but I suspect the quantification is linked to the indefinite article ‘a’ more than the verb.
> To make this concrete, if I say "he is bad" then it is unclear whether I am saying that person is an intrinsically bad man, or if I am just commenting that the thing that he is doing right now is not morally justified.
This ambiguity isn’t limited to the copula, though. ‘I like him’ has exactly the same kind of ambiguity.
> If I say "she came from school" it is clear that we're talking about relative motion today or in the recent past from one nearby location to another.
Unless we mean that she came from one school of philosophy or art to another. Or she came from the school long ago to move somewhere else.
> If I say "her family came from Japan" it is clear I'm talking about ancestry and/or a long ago emigration
Unless her family came from Japan as part of a cruise before going to Thailand. Or her family moved out of Japan because they were American military stationed in Okinawa.
Getting rid of copula gets rid of only a small portion of the ambiguity in natural language.
Yup. One man's "overuse" and "source of mistakes" is another man's way to draw attention towards a region in the latent^H^H^H^H^H^H idea space.
This is useful and often good enough, because a) the rest of what's been said and situational context will help home in on more specific associations (and if not, one can always ask for clarification), and b) we often don't need to resolve specific ideas - "my friend is a samurai" may just be an invitation for the other person to reply "oh, fun, speaking of more ancient cultures, have you read about ...", and then continue jumping around big clusters of associations, without ever properly resolving any.
If you say "My coworker Taro is a samurai", what does that mean? Did he dress up as a samurai for the office costume party? Does he study older forms of Japanese martial arts? Was he descended from a noble family from the Japanese feudal era and have claim to an actual samurai title?
There are controlled dialects of English, like E-Prime, which forbid the use of the copula "to be" as ungrammatical, or at least heavily restrict it. You can say your coworker "dressed as a samurai", "trains in the arts of a samurai", or "traces ancestral lineage from a samurai clan", but you can't say he "is a samurai" in E-Prime.
Would this make communication more clear with fewer mistakes? I don't think this has been adequately studied enough to say for certain. But at least in certain domains like military speech and air traffic control we have examples of such enforced language simplification resulting in measurable decreases in miscommunications. I'm very curious to see if we can generalize those results to a full, general-purpose dialect or entirely new language.