No.5507でbecauseの前のコンマの有無について議論が行わておりますが、正しい方向の抑制の効いた見解が、初心者向けの単純化された文法知識を鵜呑みにした人々の乱暴な決め付けによって黙殺されそうになっていることを危惧し、筆をとりました。他者の意見を間違いと決め付ける前に、無知と傲慢は表裏一体であることに気づいてもらいたいと思います。本来ならNo.5507のところに書くべきですが、書き込めなくなっているのでここに書きます。

文法的には、becauseの前のコンマの有無はwhichの前のコンマと同じで、後の文が先の文を限定するか否かで決まりますが、becauseの場合はたいてい先行する文を限定することになるので、初心者向けには「becauseの前のコンマは使用不可」と単純化して教えることが多いようです。ただし、これは「こう書けばまず間違えない」という、「初心者用の綴り方」を示したものであって、ネイティブが生成する自然な英語に通用するという意味での正しい文法ではないことに注意する必要があります。

なお、becauseの非制限用法の例は見つけにくいのですが、次のようなものはいかがでしょう。
1)は非制限用法なのでコンマが必要ですし、2）は制限用法なのでコンマは使用不可です。無理やり１）を制限用法とみなしてコンマをはずすと意味が変わってしまいます。

1) My wife found a Japanese restaurant in our neighborhood, but we did not have a chance to try it. Yesterday we had lunch there with an old friend of mine, because we happend to see him on the way to the restaurant.

2) We invited an old friend of mine to have lunch together because we happened to see him on our way to a restaurant.

コンマが必要な例の追加です。下の例の場合はbecauseの前にコンマがないと意味を成しません。一般にbecause以下が原因でなく説明だと非限定的になるのでコンマが必要です。

Now he surely loves her, because everything is felt meaningless to him without her. 　

トピズレですが・・・
５５０７の討論見ました。native-English のプロの編集者にこの件について訊きました。「A, because B」はその文のポイントが曖昧またはややこしいくなるため、文法的には間違いではないですがbecauseのこの用法を避けるそうです。 　

情報ありがとうございます。たしかに、正確な情報や論理が重視される学術誌の編集などでは、わかりやすい簡潔な英文にするために、基本的に避けるべき表現だと思います。コンマがある場合のbecause以下は付加的な情報で、削除しても大筋の意味は通じますし、説明も後知恵の場合は論理を混乱させる可能性があります。

しかし、感情や思いを伝える手紙などでは結構この表現が有用な場合があるように思います。また、日常会話は文字になっていないので気がつきませんが、becauseの前に間をおいたりbecauseをゆっくり発音しながら考えていたりする時は、たいてい後知恵の説明を語るので、文字にすればコンマつきのbecauseだと思います。
　

再度そのエディターに訊きましたが日常会話的な「感情や思いを伝える手紙」程度のものなら、自分がそこにカンマが必要だと思えばつければいいそうです。早い話、その程度のもので「カンマ云々」とこだわる人はいないでしょとのことでした。 　

そうですね。ネイティブなら文法など意識しなくても、通常は意図したとおりの意味が伝わるでしょうから。しかし、コンマの有無で意味やニュアンスが変わることに書き手が気づかない場合もあり得るので、手紙でも誤解を生む可能性はあるでしょう。
いまWebを検索してみたら、
The Chicago On-line Manual of Styleに
He didn’t run, because he was afraid.
というのが例としてあげられていました。コンマがないと走ったのかどうか分からなくなります。
　

> He didn’t run, because he was afraid.
>というのが例としてあげられていました。コンマがないと走ったのかど>うか分からなくなります。
This is obvious within the context, so nobody usually relies on the comma for that distinction.
"I didn’t run because I was afraid, but because I had to pee!"

　

Yes, but "I didn’t run, because I was afraid" can only mean, regardless of context, if the vreader wants to be logical, that the reason I didn’t run was that I was afraid, while "I didn’t run because I was afraid" means that even if I did run, it was not because I was afraid. In the latter case you need the context to know whether the person did or didn’t run. 　

Dear BovineHat, I really appreciate the example you gave us by accident.
Since your comments on various topics in this website testify your excellent ability of the language, your comment here shows us how the use of "because" with a preceding comma is misleading.
In this case we had better write "Because he was afraid, he did’t run." 　

I guess I’m a bit confused, but what I wanted to mean by
that is, "I ran not because I was afraid but because I had
to pee (run to the nearest toilet)," in a colloquial way.
I believe it’s possible depending on where you put the
stress (of course only when you say it).

　

Probably the way I wrote in Res.5 was not clear enough to prevent confusion.
What I wanted to say in Res.5 was that:
If we WRITE "He didn’t run, because he was afraid," then it is obvious that he did not run, because (sorry for using this comma preceding "because") the clause led by the "because" gives merely additional information, but if we drop the comma and WRITE "He didn’t run because he was afraid," then it means exactly what you wrote, where the theme becomes about the reason of running, not the running itself -- it even does not indicate whether he did or did not run. 　

I see your point and believe you’re technically correct.
My rather non-technical but practical point is that even in technical writing you’d make sure to clarify any ambiguity caused by such technicality, especially if the possible interpretations are polar opposites. In most cases such sentences as "I didn’t run because I was afraid," are explanation for the known fact whether you ran or didn’t run, or an answer to the question why you ran or didn’t run. That’s why I said we can’t rely on the presence or absence of a "comma" for making such major distinctions.
Am I digressing from your intention of this topic?

　

I agree with you that we should try to avoid logical ambiguity and misleading expressions in what we say or write.

I also think that we should avoid illogical expressions even if the writer’s intention is obvious by the context, and thought that "He didn’t run, because he was afraid" was too illogical to mean what you described although you wrote comma would not be important for the reader.

I have read your Res.6 again, and now guess that you wanted to mean that my comment "there is no knowing whether he did or did not run" is unrealistic because it would be obvious from the context that he actually ran.

I deeply apologize for both my misleading writing and having misunderstood your intention.

I should have written "the meaning becomes completely different by removing the comma" to avoid the digression. The theme was the existence of a sentence where the comma preceding "before" is crucial to its meaning, but not whether he did or didn’t run.

Anyway, the main topic is the necessity of sensible discussion on "the comma preceding the word before," and I really appreciate your contribution.
　

For "before" read "because" in the last two paragraphs in Res.12.

"The Chicago On-line Manual of Style" in Res.5 was "The Chicago Manual of Style Online."




　

In Res.5 I meant that:

"He didn’t run, because he was afraid" indicates that he did not run, but "He didn’t run because he was afraid" does not logically indicate by itself whether he did or did not run (on the contrary, it is almost obvious that he actually ran!)

BovinHat’s comment in Res.6 just removed the parenthses of the last part, but I did not realize it because it said "nobody relies on comma."

I should have written "However, it is the removal of the comma that produced the context you rely on."
　

I found a website discussing on the comma preceding "because."

http://forum.wordreference.com/showthread.php?t=350450

Native English speakers are answering to the question asked by a Ukrainian. According to them, the comma preceding "because" is necessary for a long complicated sentence even if the formal grammar does not require it, and there is a gray area where the comma is optional.