couldn't have done还是 couldn't

moseedam

如果我想表达“我早上的时候不可能知道晚上会下雨的”
) D+ s* C. y7 ~# o+ k/ h这句用英语怎么说？

I couldn't have known this morning that it would rain tonight.
' @3 h. |) T# }9 @. i还是
I couldn't know this morning that it would rain tonight.

zhuode

I couldn't have known this morning that it would rain tonight.现在已是tonight


I couldn't know this morning whether it would rain tonight.现在未到tonight

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楼主第二句用that个人感觉说不出的别扭,或另有高见?
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zhuode

1 X* Q# U/ N) b$ f7 X# r: i' ~3 `
" ]; X' Z: `3 ^0 c6 y4 m“couldn't have done 只能是虚拟或者是表推测。但是这个语境显然没有虚拟的含义，而且也不是在推测啊”

( V/ m: m4 N1 t# \* m哇,这个太深奥了,虚拟语气学过但早忘了,个人表示无能为力
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2 ^' s$ Y% W9 K* S& Sanyone help?

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moseedam

zhuode 发表于 2018-9-20 17:16
“couldn't have done 只能是虚拟或者是表推测。但是这个语境显然没有虚拟的含义，而且也不是在推测啊”

...

( Q  J  P0 G  B比如could have done的虚拟用法
- y- d  g& [5 }9 e# E6 {  v+ ]I could have finished the homework if my friends hadn't come.
要是朋友没来，我就能写完作业了（但事实上朋友已经来了，而且作业也没完成）
# _; H( t; \9 }5 m" i
- Q5 W+ a4 T0 v表推测的用法
They could have received our letters yesterday.
" @9 ]4 p3 h# M5 ?) I他们昨天可能已经收到我们寄出的信了。（就是一种对过去的猜测，猜他们可能是已经收到了，但并不很确定是否真的收到了。如果想表达很肯定的猜测可以说They must have received ... yesterday.但再肯定也只是猜测，除非你说They have received our letters或They received our letters yesterday. 才能表达客观事实，而不再带有推测的含义。）

trivialstuff

我个人觉得这两种说法都可以。
1. Couldn't do有表示past impossibility的用法。
( I' ]6 i& q: o, N2. Couldn't have done表示past impossibility时，给我比较强的潜台词意味，我会倾向于补充更多细节。 （更新：感觉这个语境里还带了层but now I know的意思。）比如I couldn't have known this morning that it would rain tonight (, because the weather was so damn good. But now I know. It's already started raining, and the weather forecast says it's going to be all night long).

pearsonlongman.com也对couldn't have done的用法作了一番解释。
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1. Couldn't have expresses past impossibility of an idea being true.
2. In addition to its use in full past hypothetical conditionals, as Rachel has explained, it is found in incomplete conditionals, utterances in which the if- clause is merely implied.
2 u. T  m# H; o# ^6 _1 b  h* u3. Non-conditional uses of couldn't have abound. It occurs to express impossibility in past time narratives or commentary.
. Z" ^2 {1 o5 X2 I4 R% h4. With actions that take some ability or skill, it means didn't have the ability or skill to.
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5 \9 D% R0 Q+ X- [针对第三点给出的例句：
' x0 Q) X. x4 v(l) [He] couldn't have known that just six hours later, he, the only male flight attendant on American Airlines Flight 11, would die suddenly when...
3 A+ N3 C( P" _$ ^1 g9 L3 l(m) As a young woman who had never given birth before, she couldn't have known what the experience of childbirth would be like...
7 q5 M7 N2 e$ x( H9 ~" q(n) Athletic Director Edgar Johnson couldn't have known what he was getting into when he made that fateful decision to cut the Delaware wrestling program on June 18

zhuode

moseedam 发表于 2018-9-20 17:25
比如could have done的虚拟用法
/ o+ v7 J+ b* B  i' w! FI could have finished the homework if my friends hadn't come.
7 X* ?1 j# S& [) U要是朋 ...

/ D8 ]$ |  ~6 G: N  }“couldn't have done”你看下我发的图片,也可以在与虚拟语气无关的句子中出现。

zhuode

哦,我已经晕了

yuqinghuaz1

  
I couldn't know in the morning if it would  rain tonight.   表示说话时，早晨已经过去。
I couldn't have known in the morning if it would  rain tonight.  表示说话时 ，还是在早晨。

moseedam

yuqinghuaz1 发表于 2018-9-20 18:14
I couldn't know in the morning if it would  rain tonight.   表示说话时，早晨已经过去。
& J% G9 V% }8 ?I couldn't ...

: ~, O" c4 C" B" K: f+ S. K' P如果说话时间点是早晨，你为什么要用could have done呢？

trivialstuff

trivialstuff 发表于 2018-9-20 17:34
5 V# H: V( X5 S) K# r- i- E& t- v我个人觉得这两种说法都可以。
1. Couldn't do有表示past impossibility的用法。
2. Couldn't have done表 ...

$ T0 |5 N: s% b感觉couldn't have known在这个语境里带了层but now I know的意思。

类似的：I couldn't have done it without your help. (But now I did it, because of your help.)

yuqinghuaz1

moseedam 发表于 2018-9-20 18:58
8 W* [! M6 _9 P3 V1 J% m2 s如果说话时间点是早晨，你为什么要用could have done呢？

; d) ?$ v# _0 o) t8 y& p# a表示在早晨这段时间里，你站在这段时间的一个点上说的 ，到现在为止的今日早上，所以用完成时。

yuanjiaming

应该说：I didn't know...