Purpose of "のだ" in "数年も漁村に住んでて、いろんな魚種類を食べてるのだ"?


I am making this example based on some Japanese I heard about a different
subject, but the basic context is the same.

The context is that someone has lived in a fishing village for a long time. As
a result, they have eaten many types of fish:

> "数年も漁村に住んでて、いろんな魚種類を食べてる **のだ** 。"

however, I would say it without "のだ":

> "数年も漁村に住んでて、いろんな魚種類を食べてる。"

So, is it like a native speaker will not feel an **implied causation** between
(1) my having lived in a fishing village for a long time, (2) I have eaten a
lot of different types of fish _unless_ I attach the "のだ"? (1) and (2) could
be completely different thoughts in the same sentence?

What I mean by implied causation is as such:

> Having lived in a fishing village for several years, I have been eating many
> types of fish.

Because of the implied causation, I don't need to say

> **Because** I have been living in a fishing village for several years, I
> have been eating several different types of fish."




The indication of the the cause-effect relationship between (1) and (2) will
be there with or without the のだ. Why? Because that implication comes from the
particle "て" in "住んで **て** ", and the "のだ" has nothing to do with it.

Here is the relevant definition of "て" from 広辞苑:

> ㋒ 原因・理由を示す。・・・から。・・・ので。(TL: Indicates cause or reason; ...から, ...ので)

Hence: "数年も漁村に住んで **て** 、いろんな種類の魚を食べてる(のだ)。" ＝ "数年も漁村に住んでる **から**
、いろんな種類の魚を食べてる(のだ)。"

* * *

I imagine your confusion comes from reading that sometimes のだ is used to give
reason or to add an explanatory tone to a statement. This is true; however
(therefore?), in the case of your example "数年も漁村に住んでて、いろんな種類の魚を食べてるのだ。", it is
the sentence as a whole that serves as the reason/explanation of the prior
statement (which was not included), since it attaches to the main clause
"いろんな種類の魚を食べてる".

Let my slightly awkward example help illustrate this point:

> 「 **僕は魚の味には少しうるさいよ。** 数年も漁村に住んでて、いろんな種類の魚を食べてる **んだ** 。」(I'm a bit fussy
> when it comes to tasting fish; having lived in a fishing village for several
> years, I've eaten many types of fish.)

Here, the "んだ" points back to the previous sentence "僕は魚の味には少しうるさいよ", casting
"数年も漁村に住んでて、いろんな種類の魚を食べてる" as the explanation for it. (I thought "んだ",
contracted form of "のだ", was more in step with the casual tone of the speaker
so I changed it.)




The indication of the the cause-effect relationship between (1) and (2) will
be there with or without the のだ. Why? Because that implication comes from the
particle "て" in "住んで **て** ", and the "のだ" has nothing to do with it.

Here is the relevant definition of "て" from 広辞苑:

> ㋒ 原因・理由を示す。・・・から。・・・ので。(TL: Indicates cause or reason; ...から, ...ので)

Hence: "数年も漁村に住んで **て** 、いろんな種類の魚を食べてる(のだ)。" ＝ "数年も漁村に住んでる **から**
、いろんな種類の魚を食べてる(のだ)。"

* * *

I imagine your confusion comes from reading that sometimes のだ is used to give
reason or to add an explanatory tone to a statement. This is true; however
(therefore?), in the case of your example "数年も漁村に住んでて、いろんな種類の魚を食べてるのだ。", it is
the sentence as a whole that serves as the reason/explanation of the prior
statement (which was not included), since it attaches to the main clause
"いろんな種類の魚を食べてる".

Let my slightly awkward example help illustrate this point:

> 「 **僕は魚の味には少しうるさいよ。** 数年も漁村に住んでて、いろんな種類の魚を食べてる **んだ** 。」(I'm a bit fussy
> when it comes to tasting fish; having lived in a fishing village for several
> years, I've eaten many types of fish.)

Here, the "んだ" points back to the previous sentence "僕は魚の味には少しうるさいよ", casting
"数年も漁村に住んでて、いろんな種類の魚を食べてる" as the explanation for it. (I thought "んだ",
contracted form of "のだ", was more in step with the casual tone of the speaker
so I changed it.)

