「こわいだから。」 versus 「こわい、だから[...]」


In an [answer on another
question](https://japanese.stackexchange.com/questions/9674/i-have-no-idea-
what-this-is-saying-can-you-have-two-topics-in-a-sentence/9676#9676),
@TsuyoshiIto wrote:

> [U]nlike commas in English, 読点 in Japanese is rarely (if ever) grammatically
> required. Authors are free to use 読点 wherever they feel that it makes sense
> to make a pause when pronounced.

And in a [comment on yet another
question](https://japanese.stackexchange.com/questions/9751/difference-
between-kara-and-n-desu#comment20586_9753), @dainichi wrote:

> I think [こわいだから] might exist in some dialects, but in standard Japanese, it
> is ungrammatical regardless of formality. **Unless it's こわい、だから[...] which
> is something else.** _(emphasis added)_

What is this _"something else?"_ According to answers on two other questions
([this one](https://japanese.stackexchange.com/questions/3970/how-to-
use-%E3%81%8B%E3%82%89-and-%E3%81%A0%E3%81%8B%E3%82%89-as-
conjunctions/3971#3971) and [this
one](https://japanese.stackexchange.com/questions/4671/how-
does-%E3%81%A0%E3%81%8B%E3%82%89%E3%81%A3%E3%81%A6-usually-work/4672#4672)),
`だから` is simply `だ + から`. Therefore, I would expect `*こわいだから` to be
ungrammatical because `*こわいだ` is ungrammatical. In fact, I would expect `だから`
to only follow things that `だ` can follow.

However, I'm having trouble reconciling what @dainichi and @TsuyoshiIto wrote.
If `*こわいだから` is ungrammatical, and 読点 aren't required, how can `こわい、だから` be
grammatical?

Perhaps my confusion stems from the difference between these forms:

  1. *こわいだから。
  2. こわい、だから[・・・]
  3. こわい。だから[・・・]

Can `だから` be explained as `だ + から` in all three cases? If so, does that mean
`だ` can begin a sentence or clause, or is `だから` somehow special? What is the
_"something else"_ referred to by @dainichi?

In short: how can I make sense of this?




I regret not writing "こわい。だから[...]" with a 句点 in my original comment.

The precise way to express it would have been: if こわい and だから are parts of
separate clauses, it can be grammatical, otherwise not.

In speech, you would usually express こわい and だから belonging to different
clauses by inserting a pause. With no pause between them (i.e. without
breaking the mora rythm), it sounds wrong.

In written language, what is "correct" is mostly a matter of style and
conventions. Maybe I originally kind of "broke the rules" by making it a 読点
instead of a 句点, but I would argue that it's not uncommon to join multiple
main clauses with 読点 instead of 句点 if they're closely related. But I think
most readers would find こわいだから without a 句点, a 読点 or a space very hard to
parse, and would assume you had made a grammatical error.

Maybe one rule of thumb could be: If originally it could have been a 句点, at
least have a 読点 or some other kind of space (the latter might be more common
in poetry).




I regret not writing "こわい。だから[...]" with a 句点 in my original comment.

The precise way to express it would have been: if こわい and だから are parts of
separate clauses, it can be grammatical, otherwise not.

In speech, you would usually express こわい and だから belonging to different
clauses by inserting a pause. With no pause between them (i.e. without
breaking the mora rythm), it sounds wrong.

In written language, what is "correct" is mostly a matter of style and
conventions. Maybe I originally kind of "broke the rules" by making it a 読点
instead of a 句点, but I would argue that it's not uncommon to join multiple
main clauses with 読点 instead of 句点 if they're closely related. But I think
most readers would find こわいだから without a 句点, a 読点 or a space very hard to
parse, and would assume you had made a grammatical error.

Maybe one rule of thumb could be: If originally it could have been a 句点, at
least have a 読点 or some other kind of space (the latter might be more common
in poetry).

