1。 问题提出

薄冰语法讨论：because, since, for   submitted at 2010-8-31 20:20:00

《英语常见共性问题解答》（2008，第一版）P253:

“It must have rained last night, ______ the street is wet.

A. since        B. for          C. because

原解：这里应选since, 因为这是一种推论。... because 则表示直接原因。... for表示强调用某事解释附加的原因。”

张道真词典引用：

It must have rained in the night for when I woke the next morning I saw the grass wet. (Du Maurier)

She must have gone out early, for she had not shown up at breakfast. (Macaulay)

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2。 所谓的依据

各网友抄录的做题“证据”,实际上是让他们自己越学越糊涂的一些资料：

Michael Swan:

because

A because-clause can be used to say how one knows something.
You didn't tell me the truth, because I found the money in your room.
(= ... I know because I found ... )

for
For introduces new information, but suggests that the reason is given as an
afterthought. Afor-clause could almost be in brackets. For-clauses never come
at the beginning of sentences, and cannot stand alone. For, used in this sense,
is most common in a formal written style.
I decided to stop and have lunch - for I was feeling hungry.

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1963年版《中国学生英语典型错误分析》（上海外国语学院英语系英语教研组编，上海教育出版社）581条：

...

注意这里for引导一个说明，不可换用since或as。又如：

It is morning, for the birds are singing.

The temperature must have fallen considerably, for I see icicles on the trees. 

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3。 我的解答（理论）

这几个词多年来，已经给那些所谓的专家学者弄得乱七八糟了。

薄冰，张道真也给人廉颇老矣的感觉，闭门造车，会坑害死那些学子的。

其实，以我与老外的交流经验看来，这几个词真的没那么复杂。 

有幸看此帖的朋友，记住下面的这几条，你就是使用这些词的超级高手了：

1.相对而言，because简单明了，自然也就是多用的词（一个宏观上很简单的道理嘛，很多人就是不悟）；

2.它们表"因为"时，意思一样，你给我大胆地换用，但也要稍微注意一下下面的几个关键点：

3.不要用for开始一个句子，用for属于很正式的语体；

4. 注意since表“因为”时，不要有"自......以来"的含义；

5. as做“因为”解时，可以归于书面用语，且多放于后句，用在句首也没大的关系，

但要注意不要让as有了“就在这个时候”的含义。

6. why-because这个大家都知道的配对问题； 

例外， Swan所谓的以“听者知道不知道”之类的区分方法，也是很奇怪的说法，不必理会。

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4。 我的解答（实例） 

【薄冰题】

正确答案：ABC； since可以是因为它与时间无关。

薄冰这里的解释根本没是牵强附会，可能他自己都不明白在说什么。他的语法书经常有些胡说八道的东西。

【张道真句子】

张引用的句子，并不表示就排除其它的词。 

句1， because, for, as，since

句2， because, for, as, since

【中国学生英语典型错误分析】

这种题，不要再用什么直接原因，解释性原因来解题（或说理解），否则你只能让自己糊涂。

要知道这种for本来就接近文言了，是很正式的文体。 

1. morning与鸟语没什么关系，用个and就OK了

2. 这句不自然，感觉说话者像白痴。 既然是白痴级英语水平，那because 最可能, for, since, as也可以

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5。 进一步的例题

1. I didn’t go to school yesterday _____I was ill.
 because / for / as / since

它们的意思都是 "because" 而且 "since" 不是“自...以来”的含义.
      在 "yesterday"后面应该加个逗号
2. _____ everybody is here, let’s begin our meeting.

Since / as

这里不能用"because" 以及 "for".
3. _____ you are in poor health, you should not stay up late.
Since / Because/ As

不能用“for”
4. I asked her to stay to tea, _____ I had something to tell her.
 for / because/ since/as
5. _______ it is raining hard now, let’s stay at home doing something else instead.
Since / As / becauce

不能用“for”
6.It must have rained outside last night, ______ it is wet on the ground now.
for / because/ since/as

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6. 补充题(1)

A. For       B. Because        C. Since          D. As
1.  ---Why didn't you attend the party last evening?
     ---_____I had an unexpected visitor.
2. _______ we were young, we used to talk and play together.
3. _______ we have no money, we can't afford such an expensive machine.
4. _______ it’s raining, we’d better stay indoors.
5._______ you are here, you’d better stay.
6._______ the weather is so bad, we have to delay our journey.
7. _______ it is too late now, let's go without him. 

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7. 补充题(2)

本次练习，强调标点的用法

1. _____ everybody is here, let’s begin our meeting.
Since/ As

"Since" 是个很好的选项；随便些的用词是As.
2.______ we have not enough money, we can't buy it, I'm afraid.
Because/Since/As

句首不能用for
3.I left early,____I had a long drive.
because, since, as， for

because, since, as用于后句时，不需要逗号；用于句前则必须要

for用于后句时，则必须要逗号
"for" 是等立连词， 它的通用规则是，在后半句时，前面要有个逗号与前句分开

这句用because 时，最好不用逗号, 但用since 或 as，用逗号较好，有助于消除误读.

>>>> 涉及这几个词的有关标点一般的用法

当 "because", "since",或 "as" 引导的从句用于句首时, 主句前要有逗号:

Because I eat too much, I'm fat.

Since I hate vegetables, I hate salad.

As I don't like to read, I hate my class in English literature.
从句位于后半部分时，不需要逗号

I'm fat because I eat too much.

I hate salad since I hate vegetables.

I hate my class in English literature as I don't like to read.

4.Someone must have entered, _____the lock on the door has been broken
because, as, since，for,

前3个词都可以，最好不要用for;

这里的逗号也不需要

这题里，最好都用逗号，甚至是用because时也要，避免误读成"entered because of the broken lock". 因为这句要表达的是 "we can surmise（猜测） ... from the evidence of the broken lock".

第4题里不用for, 简单地说，是等立连词for已经不太用于“A事件由B事件导致”这种语义了. 现在人们多用从属连词 "since" 及 "because" , 以及 "as".

现在人们听到第4题中用for,会觉得有些怪异，当然，不可否认，在语法上用for 并没有错.

5.It is morning, ____the birds are singing.

for/ and

两个词都对，但意思不同

It is morning, for the birds are singing. = It must be morning because I can here the birds singing.
It is morning, and the birds are singing. = It is morning, and the birds are also singing. 这句话是说，我不是再说因为我听到鸟叫所以我知道现在是早晨了，相反，有两个事件在发生，但这两件事相互之间未必会有什么关联.