"何を言っている __のか__ 、分からない" vs. "何を言っている __なのか__ 、分からない"


In the recent thread titled [Reason for 「のか」 and 「かもしれません」 in
「何を言っているのかわからないかもしれませんけど」](https://japanese.stackexchange.com/questions/18960/reason-
for-%E3%81%AE%E3%81%8B-and-%E3%81%8B%E3%82%82%E3%81%97%E3%82%8C%E3%81%BE%E3%81%9B%E3%82%93-in-%E4%BD%95%E3%82%92%E8%A8%80%E3%81%A3%E3%81%A6%E3%81%84%E3%82%8B%E3%81%AE%E3%81%8B%E3%82%8F%E3%81%8B%E3%82%89%E3%81%AA%E3%81%84%E3%81%8B%E3%82%82%E3%81%97%E3%82%8C%E3%81%BE%E3%81%9B%E3%82%93%E3%81%91%E3%81%A9),
my impression is that saying "何を言っている **のか** 、分からない" sounds abrupt (and sort
of impolite). While I have no idea if this is correct Japanese, I would have
said "何を言っている **なのか** 、分からない". The "な" seems to take the edge out of the
straight-up "のか".

The answer to the thread titled [「なん」as a formal, spoken, suffix for
questions?](https://japanese.stackexchange.com/questions/13470/%E3%81%AA%E3%82%93-as-
a-formal-spoken-suffix-for-questions) mentions the phrase "なのか". But, I can't
figure-out if that answer is applicable to my desire to say "何を言っている **なのか**
、~" instead of just "何を言っている **のか** 、~". I also found this thread titled [What
exactly is なの(nano)?](https://japanese.stackexchange.com/questions/514/what-
exactly-is-%E3%81%AA%E3%81%AE-nano). That thread looks relevant to my
questions in this thread, did it really only confuses me.

>   1. Is it even possible to say "何を言っている **なのか** 、分からない"?
>   2. Would saying "なのか" make the sentence less formal?
>   3. Would saying "なのか" make the sentence less aggressive / abrupt? more
> polite?
>   4. Would saying "なのか" make the sentence sound more feminine?
>   5. Would a native speaker actually ever say "なのか" in this type of sentence
> in a conversation?
>




[As I wrote in reply to kingyo's
question:](https://japanese.stackexchange.com/q/13470/1478)

[code]

    　どこ **だ**　＋　のだ　＝　どこ **な** のだ
    
[/code]

That is, な is the 連体形 of だ used before the formal noun / nominalizer の.

In this case, だ is simply not possible:

[code]

      *何を言っている **だ**
    
[/code]

Generally speaking, you can't follow a verb with だ like this. And so the
longer sentence:

[code]

      *何を言っている **なのか** 分からない
    
[/code]

is ungrammatical for the same reason. Since it's ungrammatical, I don't think
any of your other questions are relevant.




[As I wrote in reply to kingyo's
question:](https://japanese.stackexchange.com/q/13470/1478)

[code]

    　どこ **だ**　＋　のだ　＝　どこ **な** のだ
    
[/code]

That is, な is the 連体形 of だ used before the formal noun / nominalizer の.

In this case, だ is simply not possible:

[code]

      *何を言っている **だ**
    
[/code]

Generally speaking, you can't follow a verb with だ like this. And so the
longer sentence:

[code]

      *何を言っている **なのか** 分からない
    
[/code]

is ungrammatical for the same reason. Since it's ungrammatical, I don't think
any of your other questions are relevant.

