Is this ~もので a grammar pattern?

Question

I came across this JLPT N1 sentence:

人生はなにが幸いするかわからないもので、たぶん、あれはあれでよかったんじゃないかと思う。

My literal translation:

Life is a thing in which we don't know what will prove fortunate, but I think this is probably good in its own way.

What nuance, if any, does ~もので produce here?

It seems like もの is used strictly as a noun to mean "thing", but that seems too simple for JLPT N1 (although maybe it's a red herring). I know there's a breadth of 「もの」grammar patterns, especially ~ものだ, where this ~もので would be the continuative form. For example the usage of ~ものだ implying "general tendencies and cold facts". Coincidentally, a Japanese dictionary entry for 「幸いする」 includes an example sentence with near-exact phrasing (https://dictionary.goo.ne.jp/word/%E5%B9%B8%E3%81%84%E3%81%99%E3%82%8B/), leading me to believe that this may be a proverb.

(Sentence link: https://japanesetest4you.com/japanese-language-proficiency-test-jlpt-n1-grammar-exercise-9/, #2)

Answer 1

This もので is the continuative form of ものだ, and this ものだ is used to introduce a well-known fact or saying with a little bit of emotion. I think the first three usages explained in this answer are all somewhat relevant. This type of ものだ is commonly used especially with advice based on tradition, morals or experience. I don't think there is a perfect equivalent in English, but maybe "indeed" is close to the nuance of this ものだ.

人生はなにが幸いするかわからない is not an idiomatic fixed proverb, but it's something we often hear. (By the way, there is a proverb that exactly means this.)