Explanatory 「の」 particle being used twice in the same phrase


I was reading [**Tae Kim's Guide to Learning Japanese** on the explanatory 「の」
particle](http://www.guidetojapanese.org/learn/grammar/nounparticles#part5)
and was following it very well. I was able to understand the usage of the
**の** particle in the end of sentences to add an explanatory tone. Then, Tae
Kim explained that it's possible to conjugate the **の** particle itself,
creating the following:

  * **んだ** (plain)
  * **んじゃない** (negative)
  * **んだった** (past)
  * **んじゃなかった** (past-negative)

Although confused in the beginning, I believe I was able to understand that as
well. _Except for one example:_

                                         ![](https://i.stack.imgur.com/YNEYo.png)

                   _(Taken from<https://www.youtube.com/watch?v=obOAAmHHHVI> @ 08:12)_

**Let's look closely to sentence A.** _(I have no problem with sentence B, I
left it there for completeness.)_

**Why Tae Kim needed two の particles (separately highlighted in red)?
Shouldn't one suffice? Worse, isn't using two wrong?**

This seems like a double explanatory tone. In my point of view, the sentence A
should be **日本 と 同じ なんじゃない** instead of **日本 と 同じ なんじゃないの**.




じゃない as "isn't it?" is rather special because it can be appended to
practically anything and still be grammatically correct. Also, the two
locations of の are serving different purposes. 同じなの is giving the explanation
of being the same (Tae Kim would probably translate it as "the thing is, it's
the same"), and じゃないの is making じゃない less rhetorical and more inquisitive.

Repetition of concepts doesn't necessarily make things grammatically incorrect
either. Consider the English phrase, "It is, isn't it?" which brings up
another point - casual spoken language is much less strict with grammar than
essays/formal writing, and Tae Kim is demonstrating casual spoken language
with that example. In that case, the best measure of correctness would be a
native speaker's approval.




じゃない as "isn't it?" is rather special because it can be appended to
practically anything and still be grammatically correct. Also, the two
locations of の are serving different purposes. 同じなの is giving the explanation
of being the same (Tae Kim would probably translate it as "the thing is, it's
the same"), and じゃないの is making じゃない less rhetorical and more inquisitive.

Repetition of concepts doesn't necessarily make things grammatically incorrect
either. Consider the English phrase, "It is, isn't it?" which brings up
another point - casual spoken language is much less strict with grammar than
essays/formal writing, and Tae Kim is demonstrating casual spoken language
with that example. In that case, the best measure of correctness would be a
native speaker's approval.

