Why is intentional form used in 「カラオケに行こうと誘われました」?


> 近所のひとにカラオケに **行こう** と誘われました。

I can easily understand what this sentence wants to tell me, but I don't
really understand why intentional form is used here. I usually would just use
plain form いく.




The form with _-ō_ isn't just for intentions (the intentional mood). It's also
for invitations, i.e. an encouragement to do something together (the
**cohortative mood** , like English "let's").

To understand the sentence, first we have to consider that the clause before と
is a quotative argument. Xと誘われました means "I was invited to 'X'", where I put
quotes around 'X' to emphasize how the particle と works; it takes complete
sentences and treat them as quotations. That isn't done as often in English,
but the structure is parallel to: "A neighbor invited me, like, 'let's go to
the karaoke!'." – except in Japanese it doesn't sound casual or slangy; it's
just a normal, unmarked way of expressing the idea.




You should parse it this way:

> 近所のひとに『カラオケに行こう』と誘われました。

( _lit._ ) I was invited by my neighbor, (saying) "Let's go to Karaoke."  
⇒ My neighbor invited me out to Karaoke. / suggested we go to Karaoke.

* * *

> I usually would just use plain form いく.

You could rephrase the sentence as:

> 近所のひとにカラオケに誘われました。

I was invited to Karaoke by my neighbor.  
⇒ My neighbor invited me out to Karaoke.

... but I can't think of a natural way to rephrase it using the plain form いく.

