のだから vs のだ (んだから vs んだ）


When I learnt this grammar point a while ago, my teachers told me not to use
it with "から". There reasoning for this was that のだ already implies a reason or
supporting information for a conclusion.

Even reading through the answers for "[What connotation does なんだ
add?](https://japanese.stackexchange.com/questions/1859/what-connotation-does-
add)", it appears のだ is contrasted with から.

However, I see and hear this construction (んだから）all the time. It doesn't seem
very rare at all, which leaves me confused as to why my native Japanese
teachers told me that it was incorrect in the first place.

I'll use the first result from Google as the example.

> お兄ちゃんのことがぜんぜんすきじゃないんだからねっ！！

This is a title for a movie. However, how would this be different if the title
had have been:

> お兄ちゃんのことがぜんぜんすきじゃないんだっ！！

If のだ is used as a way to indicate reason, then why is から also included? When
would it be correct to use のだから instead of のだ?




Perhaps your teachers told you ～のだから (～んだから) is incorrect not because it is
never used (you already know it's very common) but because you can't simply
drop it into any sentence.

While digging around on Google, I came across [a very nice
PDF](https://web.archive.org/web/20130120054607/https://www.jpf.go.jp/j/japanese/survey/tsushin/grammar/pdf/grammar201009.pdf)
published by the Japan Foundation which explains the use of ～のだから. You can
read it on your own (it's even got 読み仮名!), but I'll summarize the main points
here.

### Rules for ～のだから

  1. Used when _both the speaker and listener know some fact_ , but expresses a strong feeling on the part of the speaker that the listener, although conscious of said fact, _does not fully appreciate its implications_. (I have also seen this expressed as a _mismatch between the speaker's and listener's perception of some matter_.)
  2. The clause following ～のだから often expresses the speaker's judgment, intent, wish, or request.

### Example 1

A mother tells her children, 「10時半のバスに乗る **から** 、早く支度しなさい。」 ("We're taking the
10:30 bus, so hurry up and get ready to go."). The children, however, are
occupied with other things and don't do much in the way of getting ready. So
the mother comes back and says, 「10時半のバスに乗る **んだから** 、早く支度しなさい。」 ("[Hey, I
know you know] we're taking the 10:30 bus, so hurry up and get ready to go.").
～から is used in the first sentence because it's new information and simply
provides a reason for the latter clause. But ～のだから is used in the second
because the children are aware of the fact that they're taking the 10:30 bus,
yet their failure to get ready to leave shows that they don't fully appreciate
its importance. ～のだから adds emphasis and serves to pull the listener's point of
view around to the same side as the speaker's.

### Example 2

A student comes up to a teacher and says, 「用事がある **んですから** 、早めに帰りたいんですが。」 ("I
have a prior obligation, so I'd like to leave early [if I could]…."). The
teacher feels offended by this, because the use of ～のだから implies that the
teacher should be aware of the fact that the student has something scheduled,
when in fact the teacher has no such knowledge. (A better sentence would be
「用事があります **ので** 、早めに帰りたいんですが。」 because ～ので does not presume that the listener
already knows whatever precedes ～ので.)

There's a four-problem quiz in the linked PDF which is left as an exercise to
the reader.

### お兄ちゃんのことがぜんぜんすきじゃないんだからねっ！！

Context would help a bit here, but just as a guess, this is best filed under
the "mismatch between perceptions" category of ～のだから: お兄ちゃん sees his 妹's
actions as signs that she might actually like him, but in reality that's not
the case, so 妹 decides to set the record straight and make sure she and お兄ちゃん
are on the same page with ～のだから (the implication being that お兄ちゃん should be
well aware of this fact, but from 妹's perspective, he doesn't seem to be fully
appreciative of it).




Perhaps your teachers told you ～のだから (～んだから) is incorrect not because it is
never used (you already know it's very common) but because you can't simply
drop it into any sentence.

While digging around on Google, I came across [a very nice
PDF](https://web.archive.org/web/20130120054607/https://www.jpf.go.jp/j/japanese/survey/tsushin/grammar/pdf/grammar201009.pdf)
published by the Japan Foundation which explains the use of ～のだから. You can
read it on your own (it's even got 読み仮名!), but I'll summarize the main points
here.

### Rules for ～のだから

  1. Used when _both the speaker and listener know some fact_ , but expresses a strong feeling on the part of the speaker that the listener, although conscious of said fact, _does not fully appreciate its implications_. (I have also seen this expressed as a _mismatch between the speaker's and listener's perception of some matter_.)
  2. The clause following ～のだから often expresses the speaker's judgment, intent, wish, or request.

### Example 1

A mother tells her children, 「10時半のバスに乗る **から** 、早く支度しなさい。」 ("We're taking the
10:30 bus, so hurry up and get ready to go."). The children, however, are
occupied with other things and don't do much in the way of getting ready. So
the mother comes back and says, 「10時半のバスに乗る **んだから** 、早く支度しなさい。」 ("[Hey, I
know you know] we're taking the 10:30 bus, so hurry up and get ready to go.").
～から is used in the first sentence because it's new information and simply
provides a reason for the latter clause. But ～のだから is used in the second
because the children are aware of the fact that they're taking the 10:30 bus,
yet their failure to get ready to leave shows that they don't fully appreciate
its importance. ～のだから adds emphasis and serves to pull the listener's point of
view around to the same side as the speaker's.

### Example 2

A student comes up to a teacher and says, 「用事がある **んですから** 、早めに帰りたいんですが。」 ("I
have a prior obligation, so I'd like to leave early [if I could]…."). The
teacher feels offended by this, because the use of ～のだから implies that the
teacher should be aware of the fact that the student has something scheduled,
when in fact the teacher has no such knowledge. (A better sentence would be
「用事があります **ので** 、早めに帰りたいんですが。」 because ～ので does not presume that the listener
already knows whatever precedes ～ので.)

There's a four-problem quiz in the linked PDF which is left as an exercise to
the reader.

### お兄ちゃんのことがぜんぜんすきじゃないんだからねっ！！

Context would help a bit here, but just as a guess, this is best filed under
the "mismatch between perceptions" category of ～のだから: お兄ちゃん sees his 妹's
actions as signs that she might actually like him, but in reality that's not
the case, so 妹 decides to set the record straight and make sure she and お兄ちゃん
are on the same page with ～のだから (the implication being that お兄ちゃん should be
well aware of this fact, but from 妹's perspective, he doesn't seem to be fully
appreciative of it).

