A quote from 星の王子様 (The Little Prince)

Question

There is a popular quote from the famous novel The Little Prince:

What is essential is invisible to the eye.

The Japanese translation goes something like this:

大切な物は目に見えないんだ。

I have three questions: First, invisible is "cannot be seen". Why is 見えない used instead of 見られない？

Second, what does it mean when you put: んだ in the end of the sentence? For me i wouldnt have thought about it and could have ended with みられない。

Third, 大切 is important. Since the word used in the text is essential, is it possible that there is a better word for that? Something that is one level higher than just being important? Perhaps a level like 欠かせない。

Answer 1

Q1: Because the verb 見える has more than one meaning, and it can both mean "to be able to see (something)" and "to be visible". See this question, too.

Q2: んだ is a colloquial form of のだ. See this question.

Q3: Literally, important is 大切/重要 and essential is 本質的. And according to this page, the original French version seems to contain two similar sentences, one using essentiel and one using important:

• L'essentiel est invisible pour les yeux.
• Le plus important est invisible.

The translation of the latter using important seems to be better-known in Japan. 「本質的なものは目に見えない」 would perfectly make sense, but the word 本質的 may be a bit too difficult for children.