Meaning of 運命とはわからない

Question

まる子のタコ風船は、七夕飾りのとがった部分にさわってしまい、ものすごい音ではぜてしまったのだから運命とはわからない。
Maruko's octopus balloon ended up touching a sharp part of a Tanabata decoration and burst with a tremendous sound, so ????

I'm confused about 運命とはわからない. I thought とは was used when giving a definition. So this would be "..so Maruko doesn't understand (the definition/meaning of) fate".

I think this translation must be wrong because I don't see how it can be a consequence (から) of the events described.

Answer 1

Here わからない doesn't mean "someone is not able to understand" but works as if an adjective that means "not understandable". So the translation would be like,

運命とはわからない
(What) the fate (is) is inexplicable

This usage is but an extension of perhaps more familiar wordings as follows:

大切なことは目に見えない what is essential is invisible to the eye

経済に与える影響は無視できない the impact to economy is considerable (not negligible)

Also, [story] のだから [comment] is an idiomatic(?) construction that effectively expresses the nuance of "[story], which explains how [comment]" or "considering [story], it is indeed [comment]".

Answer 2

goo国語辞書 says:

とは

2. 定義・命題などの主題であることを示す。…というものは。「友情とは、かけがえのないものだ」

So とは is not limited to giving a definition, but it can also be used to present a general expected feature of something. ("～ is always ～", "～ is supposed to ～")

Some examples from BCCWJ:

• 結婚とはするものだし、両親や親戚も彼女に結婚しろと言っている。
  (Marriage is something you (are expected to) do)
• 女とは恐ろしいものだ。天性のうそつきの化けものだ、と平太郎は痛嘆した。
  (Women are horrible beings)
• おぬしもまた、朝鮮へ明へ呂宋へ、その彼方の国々へ兵を挙げるだろう。力とはそういうものだからだ。
  (That's what power is (supposed to mean))

Answer 3

～だから

because ～

(Semantically speaking, saying 運命とはわからない when you merely bursting a balloon a bit overblown, it seems to me.)

運命とはわからない

運命 is the subject of 分からない and the whole sentence. The と before the は denotes something like というもの.