されている vs. している for certain objective verbs

Question

This has always confused me a bit and the answer might just end up being "it depends," but I was wondering if there's a way to properly evaluate this.

For example if I wanted to ask "Is this a shared PC?" I might say このPCは共有用？ and I'm not sure if that means 共有されている or 共有している。I almost always think されている sounds better but as for whether 共有する is transitive or intransitive or not - I don't know. As for which sounds stranger to Japanese people I get the impression that in the case of 共有 leaving out する and its conjugations all together is better.

I know that for intransitive verbs its simply the stative form of it, for example "It's been decided" is 決まっている rather than 決められている, but the differences in nuances of those two I think has to do with how direct you want to be, and whether the agent of the action is knowable. Obviously I might be trying to apply logic to this that doesn't work but...

Another example that confuses me:

"Is this applicable to everyone?"

みんなには適用している・されている？ 当てはまっている？

My intuition tells me that using される vs している means that there is some agent in the background or contextually that had an influence, whereas している just implies that it is a certain way. What's a good way to think about this?

Answer 1

First, 共有している doesn't mean "it's shared" but "someone shares it", i.e. 共有する is transitive only.

Second, if you are to use 決められている over 決まっている, the former sounds more like as if you are vulnerable to the one who has decided it.

Third, 適用する is transitive only and みんなには適用している？ means "Do you apply it to the rest of us?". (適用される is different from 当てはまる but that's irrelevant to this question.)

Edit: Among the verbs you listed, there's no ambiguity between their する and される forms. When it comes to verbs whose transitive version and intransitive one share the same form and have little preference in use, the される version feels like you can't control it and are excluded from the issue. This is parallel to the difference between 決まっている and 決められている.

• e.g. 計画が発動した vs 計画が発動された (the plan gets activated)