Can one say "A decides that B will do X" with ことにする?


Can one use ことにする to express the idea "A decides that B will do X"?

Take the sentence 私は外へ出ることにした. The way I see it, 私 is the subject of both 出る
and した, with one usage omitted due to being understood. So in full the
sentence is

> 私は｛私が外へ出る｝ことにした。  
>  I decided to go outside.

Now what happens if the subjects are different? Can we say

> AはBが外へ出ることにした。  
>  A decided that B would go outside.

If this construction is not allowed, how else could you say this?




I think one of your assumptions is wrong. A nominalized verb phrase doesn't
necessarily need a subject (omitted or otherwise). Take a look at the
following sentence:

> [ **嘘をつくこと** ] は良くない。  
>  [ **Telling a lie** ] is not good.

I don't think there's a recoverable subject in the verb phrase 嘘をつく. I think
it's more like "telling a lie" or "to tell a lie" than "[someone] tells a
lie". And I think the same thing is true about your example:

> 私は [ **外に出ること** ] にした  
>  _As-for me, [ **going outside** ] decided-to_  
>  = I decided [ **to go outside** ].

The nominalized verb phrase [ **外に出ること** ] talks about the idea of going
outside, but it doesn't specify an actor via a subject or anything else.
There's no subject to recover here.

The topic 私 connects to the matrix verb した, not the embedded verb 出る. Usually
a topic splits things into two parts:

> 私は ｜ 外に出ることにした  
>  topicは ｜ _comment_

This is called a _topic-comment_ structure: the comment on the right tells us
something about the topic on the left. Essentially, the topic connects with
the entire verb phrase on the right half, the head of which is した. And that's
why it can't connect with 出る, which is stuck inside a relative clause.

If you'd like to say you decided to _make_ someone go outside, you can do so
by getting rid of the intransitive 出る and putting the transitive (causative)
出す in its place (as jovanni suggested in [this
comment](https://japanese.stackexchange.com/questions/13106/can-one-say-a-
decides-that-b-will-do-x-
with-%E3%81%93%E3%81%A8%E3%81%AB%E3%81%99%E3%82%8B#comment28108_13106)). This
makes an を-role available inside the nominalized verb phrase:

> 私は [ **snailboatを外に出すこと** ] にした  
>  _As-for me, [ **making snailboat go outside** ] decided-to_  
>  = I decided [ **to make snailboat go outside** ].

But you can't directly say "A decided that B will do X", only "A decided to
make B do X". The ことにする idiom doesn't have a separate role for B to fill.

* * *

(Note: in the above, decided-to really corresponds in meaning to ことにした, not
just にした. Even though ことにする isn't a single constituent, it _is_ a single
idiom, so you can't really divide it up when talking about what it means.)




I think one of your assumptions is wrong. A nominalized verb phrase doesn't
necessarily need a subject (omitted or otherwise). Take a look at the
following sentence:

> [ **嘘をつくこと** ] は良くない。  
>  [ **Telling a lie** ] is not good.

I don't think there's a recoverable subject in the verb phrase 嘘をつく. I think
it's more like "telling a lie" or "to tell a lie" than "[someone] tells a
lie". And I think the same thing is true about your example:

> 私は [ **外に出ること** ] にした  
>  _As-for me, [ **going outside** ] decided-to_  
>  = I decided [ **to go outside** ].

The nominalized verb phrase [ **外に出ること** ] talks about the idea of going
outside, but it doesn't specify an actor via a subject or anything else.
There's no subject to recover here.

The topic 私 connects to the matrix verb した, not the embedded verb 出る. Usually
a topic splits things into two parts:

> 私は ｜ 外に出ることにした  
>  topicは ｜ _comment_

This is called a _topic-comment_ structure: the comment on the right tells us
something about the topic on the left. Essentially, the topic connects with
the entire verb phrase on the right half, the head of which is した. And that's
why it can't connect with 出る, which is stuck inside a relative clause.

If you'd like to say you decided to _make_ someone go outside, you can do so
by getting rid of the intransitive 出る and putting the transitive (causative)
出す in its place (as jovanni suggested in [this
comment](https://japanese.stackexchange.com/questions/13106/can-one-say-a-
decides-that-b-will-do-x-
with-%E3%81%93%E3%81%A8%E3%81%AB%E3%81%99%E3%82%8B#comment28108_13106)). This
makes an を-role available inside the nominalized verb phrase:

> 私は [ **snailboatを外に出すこと** ] にした  
>  _As-for me, [ **making snailboat go outside** ] decided-to_  
>  = I decided [ **to make snailboat go outside** ].

But you can't directly say "A decided that B will do X", only "A decided to
make B do X". The ことにする idiom doesn't have a separate role for B to fill.

* * *

(Note: in the above, decided-to really corresponds in meaning to ことにした, not
just にした. Even though ことにする isn't a single constituent, it _is_ a single
idiom, so you can't really divide it up when talking about what it means.)

