Why is “not knowing” 知らない and not e.g. 知っていない? [duplicate]

Question

I remember reading a bit about this topic in the answer of another post, but I specifically wanted to make this its own question:

It seems to make sense that "to know" is typically 知っている, because 知る by itself only means something along the lines of "to get to know". But going with that meaning, I can't quite grasp the logic behind "not knowing" being 知らない as opposed to, let's say, 知っていない.

Is there a good explanation for this? For example, 知る actually having a much broader meaning than what I described?

Answer 1

This is easy to misunderstand because the Vている form can mean a few things. Here are two that you're probably aware of:

1. Doing something or a continuous activity i.e.: running　走っている, eating　食べている, walking　歩いている, thinking 考えている
2. A state i.e.: the door is open　ドアが開いている, the cup is broken コップが割れている（われている）

It might be easier to think of 知っている as a verb that falls under the 1st category. As it's a continuous activity, then you can't be in a certain state if you haven't started it (i.e if you don't know something). I hope this makes sense!

Also, once you know something, you can't un-know it or stop knowing it. So while you can say to express the current state of something:
走っている
走っていない

ドアが開いている
ドアが開いていない

...It would be strange to say 知っていない。

Examples:

生徒１: 先生はどこに行ったのか、知っている？
生徒２：ごめん、知らない。

生徒１：明日は授業（じゅぎょう）がないよ。
生徒２：知っている。
生徒３：それは知らなかった。（しかし、今は知っている）

Note that 知らなかった is used, not 知っていなかった。This also reflects the verb being a continuous activity.

N.B. Just to make things more confusing, all of the below are used in Japanese and I just memorised them after failing to find a good explanation:
わかる　(to understand)
わからない (negative form)
わかっていない (te-iru form)