Why use 用いる and not 用いられる? Who’s the subject?

Question

Source: 類語例解辞典

「または」は、二つのもののうちの一方を捨てて一方だけをとる場合や、どちらでもよいという許容を表わす場合に用いる。

So the subject of 用いる is the generic “one/you/people” or is it “we, the Japanese people”? I may have overthought this but I would say it is the former, since it is just an objective definition of a word in a language, but the definition stems from how the Japanese people have been using the word.

This actually reminded me of one conversation I saw on HiNative. An American asked a 日本人 what もったいぶる means.

https://ja.hinative.com/questions/45016

「もったいぶる」は例えば、恋愛話をもったいぶってなかなかお話してくれない、とかに使います。おいしい話をもったいぶってなかなかシェアしてくれないことです。

Who does the 使う? Is it “we, the Japanese”? Or is it the generic “one/you/people”? When I am asked what a word means in my native language, I respond either with “is used” or “we use” as “we, the natives”, or even “I use” if I am not sure. When there’s no pronoun in Japanese I have trouble understanding which one of all these options fits the best into the context.

Answer 1

Why use 用いる and not 用いられる? Who’s the subject?

I think those are separate questions.

Why use 用いる and not 用いられる?

The effect is basically the same in this context, just like "You use X when ..." and "X is used when..." mean basically the same. Because 用いる is shorter, it might be preferred. But that doesn't mean the 用いられる is wrong.

Who’s the subject?

Who the empty subject and the agent in a passive sentence refer to depends on the context. In instructions, the empty subject in Japanese would probably refer to the reader. In explaining how to use certain linguistic expressions, '(native) speakers' would be the default subject. I think in English the generic 'you' works similarly.

That said, at least in instructions, I think there is a subtle difference.

このボタンは非常時に押します
このボタンは非常時に押されます

the first version sounds more like the reader is supposed to push it, while the second version makes it more neutral - it can be the reader, but it can be someone else, or it can even be automatic.

Answer 2

Since your example sentences are about the Japanese language, their implicit subject is Japanese-speaking people in general. Unlike Japanese, English is a language that requires an explicit subject. When translating such a sentence into English, you have to choose from you, one, people, or we, depending on the writing style and the type of the article, but I would say this has little to do with the Japanese language itself. You can choose whichever sounds the most natural to you.