で・と・が・は - Nuance

Question

ボブと戦ってる

Fighting with Bob (Against Bob/Bob is fighting someone, and that same someone is fighting Bob)

ボブが戦ってる

Bob is fighting

ボブたちが戦ってる

Bob and them are fighting (not necessarily together nor necessarily against the same thing)

ボブたちで戦ってる

Bob and them are fighting (together against the same thing)

ボブは戦ってる

(Lacking Context to Know, As for Bob, fighting, could replace と・が probably, or it could mean something totally different)

This is my current understanding. (The above are my own sentences) My question is, if と is used, then does that mean they are doing the action to each other? Like if you use と with Hanasu they are both talking to each other. If you use が with a verb that just means that those people are doing that verb. If you use they with a group of people like ボブたち then that means they are doing an action together, but not to each other.

And then は is super context dependent.

と - Reciprocal

が - Simply doing an action (in active sentences)

で - With a plural group of people, means they are doing the action together, but not against each other

は - Context defined

Is this understanding correct?

Answer 1

For those sentences in particular, your understanding is all right.

As for が and は, you should know there are many aspects. Roughly it is correct to assume they indicate a subject, everything else would depend on context.

For と and で, it depends on verbs and how you interpret them (or the term reciprocal). For example,

• 彼女とデートした

would mean dated with her, arguably did a date together. (You could interpret it as some sort of reciprocal activity.)

• 二人でけんかしている

would mean those two are arguing against each other, which could be interpreted as reciprocal. (You could say doing a quarrel together)

So together or reciprocal is more a matter of meaning/interpretation, and you cannot really set one meaning for particles by themselves.

Answer 2

This is not about nuances as much as it is about grammar. Particles mark values for certain slots, in this case mostly the が slot (the subject, who does the fighting) and and the と slot (the opponent of the fighting). These slots are associated with the main verb 戦う, and different verbs expect different slots with different levels of requirement (but the が slot is often highly required)^*.

Xは often brings X to the が slot. Xで doesn't bring X into any of the required が and と slots, making the sentence incomplete (not in the sense that it's ungrammatical, but it requires the context to provide the missing values).

ボブたちで戦ってる

This makes the subject (or the が slot) and the opponent (or the と slot) implicit, and has extra vagueness. The implicit subject could exactly match ボブたち, but it could be something else. There might be a larger group that is the subject of 戦う, and ボブたち might be select representatives - in that case it's reasonable to assume they are fighting together, not against each other. There might be controllers that is the subject of 戦う and ボブたち might be merely tools/puppets - in that case, they might be fighting together (under the same controller), and they might be fighting against each other (under different controllers on each side).

I'm not saying you can draw these interpretations from one particle alone, though. They will simply be possible with that sentence, while in the other sentences they will probably be incompatible with the explicit subjects (except for in some very contrived context).

ボブと戦ってる

This is kind of similar in being vague about the subject, but it at least fills the と slot.

*: This concept is called 必須格 in Japanese linguistics. I don't know what is the correct term in English - "required case value"?

How to disambiguate と

-と can be used to mean 'together with _', which is optional in a lot of verbs, in addition to the opponent slot mentioned above, leading to two possible interpretations. The required slot (the "opponent" interpretation here) usually takes precedence over the "together" interpretation, because it needs to be filled somehow, but not always. When the context heavily implies the existence of someone else on the same side to the subject, that interpretation could be preferred.