What's interesting about the replies to this comment how readily people provide post-hoc justifications for language features that often have no essential rhyme or reason. The same is true for the prepositions which accompany verbs, which tend to vary by language, but for which every language's speaker will gladly offer you "rules" or "explanations" for when they fit. It's great evidence that we can be very good at something with no communicable understanding of what it is we actually know.
> people provide post-hoc justifications for language features that often have no essential rhyme or reason.
Nah. English articles make sense, they're just usually unnecessary, and languages can often do without the information they add (or they reduce ambiguity in other ways.) English articles certainly reduce the context necessary to understand an isolated sentence.
In Spanish, for example, knowing the subject of the conversation or even knowing what's going on in the surroundings of the speaker might be necessary to understand a subjunctive. In English, hearing a definite article will tell you that you've missed something if you don't know what it refers to; hearing an indefinite one will assure you that you haven't. Hearing an article at all will assure you that the noun isn't being verbed (if it's not obvious.) It's impossible to tell what some Spanish sentences mean in isolation, because you don't know who would do, could do, should do, or was doing the thing. Means nothing in normal conversation. Koreans are like "how do you even know how old they were?" Quechua are like "how do you even know how they found out?"
There's a good reason for everything in language, because if we don't need it, it will just get dropped. The obvious purpose of a thing might not be the reason that it is necessary, though. It may plug an ambiguity hole left by other parts of the language. It may be necessary socially/religiously. It may just reduce to a tolerable level the amount of thinking one has to do before beginning to speak.
> It's great evidence that we can be very good at something with no communicable understanding of what it is we actually know.
Definitely true, but this is a bad example. English adjective order is the really good example that people usually cite. We don't even know that we're doing it. Also all of our weird grammatical tones, and our strong word/phrase -initial stress. Shifting that stuff changes meanings completely, everybody understands, nobody notices. Except people coming from tonal languages, trying their best not to sound like robots or broken tape recorders.
The "I don't know" noise, "[note]mmm[higher note]MMM[middle note]mmm," and the other weird sing songy grunts we do that are words. Our crazy vowels. The fact that the word "tests" is a voiced click and two hisses.
And that's not even getting into politeness - and the difference between modulating politeness and indexing politeness. English speakers modulate. Speakers of many Asian languages index. We change forms of address as a way to express how we currently feel about someone, whereas when a Korean person starts dropping honorifics, it almost means they don't even think you're human.
I'd add an example I basically never see discussed about English (in common discussions, it is otherwise very well studied in phonetic linguistics, and mentioned in dictionaries) - weak and strong forms - how sentence stress is indicated by shifting vowels around. For example, the word "the" is pronounced as either ðə or ði, two quite different vowels, depending solely on whether it has topic-level stress ("the question is" vs "this is the question"). Similarly, "a" is either ə or eɪ, again depending on topical stress.
I believe this is quite uncommon in European languages (a system where the same word is pronounced with different sounds based on the topic level stress assigned to it, not on basic prosody/word sequence/etc). Apparently Dutch has a similar system.
