Explanatory の/ん in questions with interrogatives: Two conflicting rules


I'm working through [this grammar
book](https://www.amazon.co.jp/%E5%BA%B5-%E5%8A%9F%E9%9B%84/dp/4883191559/),
which goes into a lot of detail about the grammar of questions and when the
explanatory の/ん needs to be included. On pg. 284, the book says that a
question must include の/ん if the following is true:

> 疑問文中に疑問語 (疑問詞) が含まれている (疑問語疑問文の) 場合

With more details further down the page:

> なお、疑問語 (疑問詞) を含んでいてもその疑問語 (疑問詞) が述語に含まれているときは名詞文と同じ構造になるので、「のだ」は必要ではありません。

In summary, a question containing an interrogative that isn't the final
predicate must include の/ん. Examples: 「田中さんは何を見た **の**
ですか。」「田中さんが見たのは何ですか。」(The book also notes that this rule isn't always followed
in beginner Japanese language education, even though sentences that don't
follow this rule would sound unnatural to native speakers.)

Edit: Just to clarify further, this rule only applies to questions as part of
a sentence's main clause. The book notes that relative clauses would not
apply. Example: 「私の留守中に **だれが来たか** 教えてください。」

But, on pg. 287, the book lists the following question forms as valid (where ↑
= a rising tone):

> だれが来ますか。  
> だれが来ましたか。  
> だれが来ます↑。  
> だれが来ました↑。  
> だれが来る↑。  
> だれが来た↑。

These two pages seem to contradict each other. How can the structures on pg.
287 be valid without の/ん, if the rule on pg. 284 is true? The book doesn't
clarify this, and I'm not sure what I'm missing.




They indeed seem to contradict each other. However, the rules described in the
preceding pages should not be taken too literally. The book itself offers the
following caveat in p286.

>
> 本来「のだ」が必要とされる文で「のだ」が使われないことがあります。この場合、「のだ」を使っても問題はないので、学習者は「「のだ」が不要になることもある」ということを知っていれば十分です。

As for the examples you copied from p287, the authors probably needed a few
examples with an interrogative that end with か (without の) in order to
demonstrate だれが｛来る／来た｝か as invalid in contrast to あの映画を｛見るか／見たか｝ with no
interrogative.

While these questions are not exactly invalid, they sound somewhat _detached_
from the situation, as if the speaker is interrogating someone for the purpose
of obtaining a fact, indifferent to the situation of that person. Depending on
the context, they could even sound a little intimidating.

The following equivalents with ん or の sound more natural in most cases.

> だれが来る **ん** ですか。  
>  だれが来た **ん** ですか。  
>  だれが来る **の** ↑。  
>  だれが来た **の** ↑。

The difference is the presence or absence of 前提 and 焦点 as the book puts them.
The _who_ part gets focused by の or ん against the background knowledge that
someone will, has, or did come and only their identity is unknown. I suppose
it is due to the lack of this focus that questions with interrogatives sound
unnatural unless they also contain の or ん.




They indeed seem to contradict each other. However, the rules described in the
preceding pages should not be taken too literally. The book itself offers the
following caveat in p286.

>
> 本来「のだ」が必要とされる文で「のだ」が使われないことがあります。この場合、「のだ」を使っても問題はないので、学習者は「「のだ」が不要になることもある」ということを知っていれば十分です。

As for the examples you copied from p287, the authors probably needed a few
examples with an interrogative that end with か (without の) in order to
demonstrate だれが｛来る／来た｝か as invalid in contrast to あの映画を｛見るか／見たか｝ with no
interrogative.

While these questions are not exactly invalid, they sound somewhat _detached_
from the situation, as if the speaker is interrogating someone for the purpose
of obtaining a fact, indifferent to the situation of that person. Depending on
the context, they could even sound a little intimidating.

The following equivalents with ん or の sound more natural in most cases.

> だれが来る **ん** ですか。  
>  だれが来た **ん** ですか。  
>  だれが来る **の** ↑。  
>  だれが来た **の** ↑。

The difference is the presence or absence of 前提 and 焦点 as the book puts them.
The _who_ part gets focused by の or ん against the background knowledge that
someone will, has, or did come and only their identity is unknown. I suppose
it is due to the lack of this focus that questions with interrogatives sound
unnatural unless they also contain の or ん.

