What are the differences between the usage of は and では in negative sentences?


I understand that in a sentence such as

> わざわざあなたが行くことはありません。誰かに行かせます。

the general meaning of ～ことはない is that there is no need to do something.

But why would it be wrong to say ではない ? Is there a complete different meaning
behind では ？

Thank you in advance for your help! :)




> Is there a complete different meaning behind では ？

I'd rather think では doesn't have much meaning compared to こと. ではない apparently
doesn't have specific meaning for unnecessity and I guess it cannot be used
with 行く from the grammatical point of view.

Let me explain in depth.

行くことはありません is separated as 行く + こと + は + ありません. こと we're using here is called
"dummy noun" (形式名詞 in Japanese). So, basically, it points to 行く and is used to
form a noun with 行く (to go). は is just a postpositional particle. Don't care
about it too much. ありません is the negative form of ある. I don't know why, but こと
seems to gain a meaning for unnecessity when it's used with the negative form
of verbs.

Next, ではない. When we want to negate the meaning of 行く, we'd say 行 **か** ない
because 行く conjugates along
[カ行五段活用](https://ja.wikipedia.org/wiki/%E4%BA%94%E6%AE%B5%E6%B4%BB%E7%94%A8).
There's no room for putting ではない right after 行く. It's just grammatically
wrong.

So, you might wonder what ではない is. I guess it's separated as で + は + ない, not
では + ない. で is part of the conjunctive form of verbs (e.g. 好き **で** + は + ない).
は here is a postpositional particle and ない just negates verbs.

In conclusion, Xではない is the negative form of verbs and it doesn't have
additional meanings other than negation. Also, putting ではない right after 行く is
grammatically wrong.

