友人と as a subject


A sentence from a blog whose host is temporarily absent from school:

> 実際に行動を起こすなら友人とがいい。

This sentence is not difficult to understand.

I was able to rule out the possibility of `がいい` here acting as a 副助詞 as in
`見るがいい`. However, I feel unsure of myself to interpret `友人と` as the subject of
this sentence, governing the `が` after it.

I've come across comparative expressions like `～と～とでは`, but this sentence
above is my first time looking at something like `とが`. I cannot wrap my head
around what constitutes a legitimate subject in Japanese.




Some particles, such as から and まで, can form noun phrases.

> 熱海 **まで** がＪＲ東日本で、その次の駅 **から** がＪＲ東海です。

Though I might have given you the impression by my comment that と works in a
similar way to them, that’s not quite the case. I think your sentence could be
understood as an abbreviated version of the following, in which the
nominalizer の, not と, is the head of the noun phrase.

> 実際に行動を起こすなら友人と（起こすの）がいい。

The original sentence doesn’t sound particularly informal. It sounds normal
enough.




Some particles, such as から and まで, can form noun phrases.

> 熱海 **まで** がＪＲ東日本で、その次の駅 **から** がＪＲ東海です。

Though I might have given you the impression by my comment that と works in a
similar way to them, that’s not quite the case. I think your sentence could be
understood as an abbreviated version of the following, in which the
nominalizer の, not と, is the head of the noun phrase.

> 実際に行動を起こすなら友人と（起こすの）がいい。

The original sentence doesn’t sound particularly informal. It sounds normal
enough.

