Question about a context sentence


#1

So one of the context sentences on this site is:

日本に住むために、まず最初に自分の親を説得しなくてはいけません。

My question is, what’s the point of using the double negative at the end when it says “説得しなくてはいけません”? I don’t question whether or not its grammatically correct, but is it common/necessary to see a double negative used like that in this case?


#2

Yes that is how you express that something has to happen in Japanese.


#3

A literal translation for this construction would be something like “if it is not thus, it can’t be”.


#4

It’s how you say something must be done/have to do:

http://www.guidetojapanese.org/haveto.html