"I hate him" = 彼が嫌い or 彼は嫌い? Ambiguity regarding the target of the sentence


I apologize if this is a dumb question. I think I'm having a total brainfart
here, but this is something I've been wondering since some time ago now.

If I wanna say, "I hate him!", which one would be more grammatical?

> 彼は嫌い

or

> 彼が嫌い

In this example, I always get myself confused as I struggle identifying who
would be the 'person hating' and who would be the 'person being hated'.

I mean, could both of these be ambiguous? As in, could they also translate as
"he hates (something)"? Can either は or が establish a difference here? And
either way, which would be more appropiate?

My brain says が is the better choice, but I'd really appreciate if anyone
could help me clear up my doubts about the target and do-er of a sentence.
It's kind of embarrasing since I've been studying for some time but I still
get tripped up over this.

Really sorry for the long post. Thanks in advance and for reading!




Either can mean “[something] hates him” or “He hates [something]” depending on
the context. “〜は” vs “〜が” in Japanese has nothing to do with subject versus
object and in fact “〜が” has surprisingly little to do with subjects either.
Japanese particles are actually very overloaded but that's the case in English
too. Consider “I am seen by him/the river/way of eyes.” where “by” is very
overloaded and in theory “I am seen by the river.” could mean that the diver
did seeing, rather than being the location the seeing happened, but that's
unlikely. Rivers do not generally see.

The problematic, but very common, part of “嫌いだ” is that it marks both it's
subject and object with “〜が”, though “〜を” for the object also occurs in some
more limited contexts. The problematic part of “〜が” is that when “followed” by
“〜は" it mandatorily “contracts” to simply “〜は" opposed to say “〜に” which
becomes “〜には”. The problematic part of Japanese is that parts of speech
readily clear from context tend to be omitted.

So “私が猫が嫌いだ” could mean “I hate cats.” or “Cats hate me.”. In practice, it
almost always means the former. “私は猫が嫌いだ” is a bit more likely to mean
something along the lines of “Cats are the things that hate me.” because
topic-fronting is fairly common in Japanese but it also more often means “I
hate cats.”

As for which is the better choice, that simply depends on whether the context
wants to make “him” the topic or not. If you're already talking about this
person in or contrasting him in some way with something else then “〜は” is more
appropriate. If you're answering “誰が嫌い？” or bringing him up out of nowhere
then “〜が” is the way to go. But what part of the sentence, if any, to make the
topic in Japanese is a very difficult thing that comes with time and exposure
that's hard to explain and it's not just the subject that can become the
topic. For instance “彼が嫌いかどうか **は** 本当にわからない” means “I really don't know
whether I hate him or not” [or “I really don't know whether he hates it or
not”] note that “〜は” here comes after “彼が嫌いかどうか” “whether I hate him or not”.
Putting “〜は” there is natural in a context where both speaker and listener are
assumed to ponder the issue. The speaker isn't introducing the topic into the
conversation at that point but commenting on it and that's fundamentally what
“〜は” does, it marks that something is already “in the conversation” in some
way rather than being introduced into it, but it need not have been explicitly
mentioned before either.

