[KyleGoetz]

Originally Posted by Sumippi

え！「ため」is a noun! あ～～。(*_*)

Thank you very much, masaegu-sensei and Kyle-sensei...

I remembered learning in high school something like 'が、の、を、に、へ、と、より、から、で、や」as 格助詞case particles...

Oh... then「ので」is not a case particle? So, if「で」in「ので」is originally 「です」＝「だ」, then if I say 「の」+「で」＋「だ」or 「の」+「で」+「です」, 「だ（＝です）」will be redundant, so 「のでだ」 is impossible, right? It'd be like 「のです＋です」or「のだ+だ」. This makes sense to me... because 「お金がなかったのです」is fine.

難しい。。。こんがらがってきた。I'm getting more confused. （^_^;）
I'll have to check my Japanese Grammar textbook from high school. 笑。

The dictionary lists ので as a 接続助詞. This is a conjunctive particle (the English equivalent is just a "conjunction"), not a case particle. Strictly speaking, a case particle marks grammatical case/function within a sentence. ので does not mark a grammatical case. Case means subject (が), topic (は), direct object (を), indirect object (へ／に), location (に／で), etc.

It's a bit tricky to talk in English about case particles since English has almost no case system left (so many readers on JF, despite being native English speakers, have no idea what we're talking about). The only real case we have anymore is the possessive case (sumippi -> sumippi's [post]). The rest we basically do with sentence order and prepositions (so you could say prepositions are almost 接続助詞 for English).

In modern Japanese, a list of conjunctive particles includes: 「ば」「と」「ても（でも）」「けれど（けれども）」 「が」「のに」「ので」「から」「し」「て（で）」 接続助詞 とは - コトバンク

せつぞく‐じょし 【接続助詞】

助詞の種類の一。用言や用言に準ずるものに付いて、下 にくる用言や用言に準ずるものに続け、前後の文（また は文節）の意味上の関係を示す助詞。現代語では、「ば 」「と」「ても（でも）」「けれど（けれども）」「が 」「のに」「ので」「から」「し」「て（で）」など、 古語では、「ば」「とも」「ど」「ども」「が」「に」 「を」「て」など。

But now I'm just rambling. I'm merely an amateur linguist.