# Could, past and present meaning: could do, could have done, ...'



## Kili

_<< Moderator note.
This thread has been formed from three that were active at the same time.
See post #43. >>_*

Sorry, I ----------you yesterday as I forgot your phone number.

*a) couldn't call
b) couldn't have called
c) wasn't able to call

Are all the alternatives possible? Which one is the best choice?


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## panjandrum

Kili said:


> *Sorry, I ----------you yesterday as I forgot your phone number.*
> 
> a) couldn't call
> b) couldn't have called
> c) wasn't able to call
> 
> Are all the alternatives possible? Which one is the best choice?


(a) and (c) are good natural sentences - though I want to write "I had forgotten" not "I forgot".

(b) would make a good sentence without the _Sorry,_ at the beginning.
I couldn't have called you yesterday as I had forgotten your phone number.

I can't explain why.


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## Kili

panjandrum said:


> (a) and (c) are good natural sentences - though I want to write "I had forgotten" not "I forgot".
> 
> (b) would make a good sentence without the _Sorry,_ at the beginning.
> I couldn't have called you yesterday as I had forgotten your phone number.
> 
> I can't explain why.


 
Helo Panj.

Does "couldn't have done" have the notion of an unfulfilled Past Ability as in the sentence, much less a Past Conclusion or Possibility. What's the difference between the following two sentences

I could have beaten him with one hand. (Does this show ability)
I could beat him with one hand.


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## quietdandelion

Kili said:


> *Sorry, I ----------you yesterday as I forgot your phone number.*
> 
> a) couldn't call
> b) couldn't have called
> c) wasn't able to call
> 
> Are all the alternatives possible? Which one is the best choice?


 

If there is one and only one choice, I'd go for c). 

As for a), it could be a possible choice.

As for c), it's quite impossible because it's a subjunctive verb form.


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## panjandrum

Kili said:
			
		

> I could have beaten him with one hand. (Does this show ability)
> I could beat him with one hand.


I could have beaten ... - an assertion past/current ability, unproven - and it will not be tested.
I could beat him ... - an assertion of past/current ability, possibly proven - and it may yet be tested.


Kili said:


> Helo Panj.
> Does "couldn't have done" have the notion of an unfulfilled Past Ability as in the sentence, much less a Past Conclusion or Possibility. What's the difference between the following two sentences.


You give some of your words capital letters as if they have formal definitions, so I hesitate to comment. I tend to confuse myself when I try to use grammatical terms with capital letters.

I have a notion that your question is related to quietdandelion's subjunctive comment. I am sure there is no such grammatical term, but "couldn't have done" is, to me, a statement of past inability, or indeed past impossibility  On the other hand, "could have done" certainly carries a sense of unfulfilled past ability (lower case) for me.

I really don't detect any whiff of subjunctive here?


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## 8769

What is the difference in meaning or nuance between #1 and #2, for the blank in the following passage?
1. could achieve
2. could have achieved_It was only five years ago that people recognized Ken Noguchi as the youngest person to scale the world’s highest peak.  Seeing him suffering from altitude sickness, yet smiling while holding a Japanese national flag at the top of Mt. Everest, they wondered how a twenty-five-year-old man (    ) such a major undertaking._​I sense some difference, but I can’t explain it well.


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## Natalisha

Could achieve.           We use perfect infinitives to show that something didn't happen. You can't use "could have achieved" because it's clear that the action was performed.


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## Prower

So if we say

*1) I could do it yesterday. *
Does it mean that I really did it? 
*If yes*, then it is not ok to say. - I could do it yesterday but I didn't. 

2) I could have done it yesterday.
Does it mean that I really didn't do it?


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## chasfh

I think the difference is this:

- It was the best he could do (meaning at that time, on that day, under those circumstances)
- It was the best he could have done (meaning ever, at any time, to the limits of his ability)


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## Prower

chasfh said:


> I think the difference is this:
> 
> - It was the best he could do (meaning at that time, on that day, under those circumstances)
> - It was the best he could have done (meaning ever, , to the limits of his ability)


1) Having read other threads on this topic I have come to conclusion that could do/could have done _deal _with the fact whether it was really done or it wasn't. I don't see that mentioned in your post. Did you forget to include it or you don't associate it with this could do/could have done thing?

2) I have never found anything backing up this distinction coming down to 

(meaning at that time, on that day, under those circumstances) VS (meaning ever, at any time, to the limits of his ability)

I wonder if this is true.

In my example I used "yesterday". It turns out that *either *we are not to use "yesterday" with "could have done" (because it means - ever, at any time - and contradicts to "yesterday") *or* "ever, at any time" is not always the case.


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## Prower

panjandrum said:


> I am sure there is no such grammatical term, but "couldn't have done" is, to me, a statement of past inability, or indeed past impossibility


1) Could you confirm or disprove my assumption.

*Could have done* can have something in common with *couldn't do.*

- I could have done it yesterday but I didn't.
- Let's call spade a spade! You couldn't do it.

Would this - *couldn't do it* - be a fair analogy of - *I could have done it.*

2) Another thing which is not clear to me is when it is reserved for - couldn't have done - to be used.

I couldn't have done it yesterday *basically can convey the same meaning as* I could have done it yesterday *conveys*. Why? Because in both cases the person didn't acomplish something. Am I righ here?

The only case when it can be used in my current opinion is in reported speech.
==========
What do you think?


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## panjandrum

Prower said:


> *1) I could do it yesterday. *
> Does it mean that I really did it?


I know that I was able to do it yesterday because I did it.
"It" might be something like ... touch my toes.


> *2) I could have done it yesterday.*
> Does it mean that I really didn't do it?


I believe that's right.
"It" might be something like ... taking Maisie to the cinema.  I can't take her today. I could have done it yesterday (but perhaps I wasn't asked).


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## chasfh

Oops--I completely botched the intent.  Sorry about that.

Here's how I think the sentence would best read:

_It was only five years ago that  people recognized Ken Noguchi as the youngest person to scale the  world’s highest peak.  Seeing him suffering from altitude sickness, yet  smiling while holding a Japanese national flag at the top of Mt.  Everest, they wondered how a twenty-five-year-old man could have succeeded in such a  major undertaking._

It's "could have succeeded" because it is contemplating the overall ability of any 25-year old to ever succeed in such an undertaking, rather than contemplating how a 25-year old man could succeed in this place, on this day, under these circumstances (all of which happen to be unspoken here).

Also, note how I substitute "succeeded in" for "achieved", as this reads better.


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## Prower

panjandrum said:


> ... touch my toes.


What does it mean here?


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## panjandrum

Prower said:


> 1) Could you confirm or disprove my assumption.
> 
> *Could have done* can have something in common with *couldn't do.*
> 
> - I could have done it yesterday but I didn't.
> - Let's call spade a spade! You couldn't do it.
> 
> Would this - *couldn't do it* - be a fair analogy of - *I could have done it.*


I think I understand what you are asking, but I'm not sure.

_I could have done it yesterday._
I had the ability or opportunity to do it, but *I didn't do it*.

_I couldn't do it yesterday._
I did not have the ability or opportunity to do it, and *I didn't do it*.

Both red sentences carry the implication that I didn't do it.
They have that in common, but otherwise they are opposites.


> 2) Another thing which is not clear to me is when it is reserved for - couldn't have done - to be used.
> 
> I couldn't have done it yesterday *basically can convey the same meaning as* I could have done it yesterday *conveys*. Why? Because in both cases the person didn't acomplish something. Am I righ here?


_I couldn't have done it yesterday._
I did not have the ability or opportunity to do it, and *I didn't do it*.

_I could have done it yesterday._
I had the ability or opportunity to do it, but *I didn't do  it*.

Again, part of the meaning is the same, the rest is opposite.


> The only case when it can be used in my current opinion is in reported speech.
> ==========
> What do you think?


I don't think there is any such restriction with these sentences.


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## e2efour

8769 said:


> What is the  difference in meaning or nuance between #1 and #2, for the blank in the  following passage?
> 1. could achieve
> 2. could have achieved_It was only five years ago that people  recognized Ken Noguchi as the youngest person to scale the world’s  highest peak.  Seeing him suffering from altitude sickness, yet smiling  while holding a Japanese national flag at the top of Mt. Everest, they  wondered how a twenty-five-year-old man (    ) such a major undertaking._​...



I see no difference between could achieve and could have achieved in the sentence in _<this post>_. Could can be replaced by "was able" and we could also write "had been able" if we want.


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## Prower

chasfh said:


> It's "could have succeeded" because it is contemplating the overall ability of any 25-year old to ever succeed in such an undertaking, rather than contemplating how a 25-year old man could succeed in this place, on this day, under these circumstances (all of which happen to be unspoken here).


I see your point. And it seems to me that you have discovered a new aspect of this issue. Before that I had been focused only on the *(1)* "a virtually done thing" vs "an undone thing". But now you have brought into the view another aspect which is *(2)**could do* - a certain occassion, a limited period of time *vs **could have done* - an unlimited period of time. 

I wonder what others think about the second aspect?


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## chasfh

Prower said:


> So if we say
> 
> *1) I could do it yesterday. *
> Does it mean that I really did it?
> *If yes*, then it is not ok to say. - I could do it yesterday but I didn't.
> 
> 2) I could have done it yesterday.
> Does it mean that I really didn't do it?



1) It does not mean that you did it -- it means that you could have done it, but you didn't.  I believe that in most cases when you say this, the implication is that you are no longer able to do it: "I could do it yesterday (but I can't do it today)."

2) Yes, this means that you didn't really do it, even though you could have.  I believe when you say it this way, this could imply either that you could still do it today: 

"I could have done it yesterday (but I could still do it today if I have to)."

Or that you can no longer do it:

"I could have done it yesterday (but I can't do it today even if I wanted to)."

It depends on the context of the conversation around it.


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## Prower

Thank you panjandrum

Seems like you have understood my concern 100%. 



panjandrum said:


> _I couldn't do it yesterday._
> I did not have the ability or opportunity to do it, and *I didn't do it*.
> 
> _I couldn't have done it yesterday._
> I did not have the ability or opportunity to do it, and *I didn't do it*.


However a new question is on the way as it is a natural continuation in this case.

You have given the same explanation to these two.

Seems like they are the same. Are they?

I couldn't do it yesterday.
I couldn't have done it yesterday.


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## Prower

chasfh said:


> 1) *it means that - (1)  you could have done it, but you (2)  didn't. *
> 
> 2) *Yes, this means that - (2)you didn't really  do it, even though you (1) could have.*


_<Emphasis added by Prower.>_

Well, I don't see much difference between these two from your description. Rather the opposite do I see. They are completely the same.


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## Elle Paris

I could not have called you yesterday. means "It was impossible for me to have called you yesterday... ( ...as I had no way of getting your number so it could not have been me calling.) It is correct only in the conditional. (I could have called you if I had had your number or means of finding it out.)
He could not have killed her because he was in prison at the time of the murder. (If he had been in her neighborhood he could have killed her, but he wasn't)
I could not have taken the bus; I was on jury duty all day long, so the person you saw could not have been me! You must have seen someone else who looked like me.
(If I had not been on jury duty, I could have taken the bus but I would more likely have driven my car.)


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## JulianStuart

chasfh said:


> 1) It does not mean that you did it -- it means  that you could have done it, but you didn't.  I believe that in most  cases when you say this, the implication is that you are no longer able  to do it: "I could do it yesterday (but I can't do it today)."
> 
> 2) Yes, this means that you didn't really do it, even though you could  have.  I believe when you say it this way, this could imply either that  you could still do it today:
> 
> "I could have done it yesterday (but I could still do it today if I have  to)."
> 
> Or that you can no longer do it:
> 
> "I could have done it yesterday (but I can't do it today even if I  wanted to)."
> 
> It depends on the context of the conversation around it.





I think chasfh's explanation is correct.

I am trying, today, to start the lawnmower.  However, I am now failing.  I explain to the repair mechanic : "*I could do it yesterday*." or "I was able to start it yesterday".

I am mowing the lawn right now.  I explain to my wife, "*I could have done it yesterday*, but got lazy." (So I didn't do it: I was able to but not willing to).

Quite different meanings.


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## chasfh

Prower said:


> Well, I don't see much difference between these two from your description. Rather the opposite do I see. They are completely the same.



I think you're correct in seeing that they could be pretty much the same, but I think the key difference is this:
1) "I could do it yesterday (but I can't do it today).": You no longer have the ability to do it, even if you had the opportunity to do so.

2) "I could have done it yesterday (but I can't do it today even if I wanted to).": You still have the ability to do it, but you no longer have the opportunity.​


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## JulianStuart

chasfh said:


> 2) "I could have done it yesterday (but I can't do it today even if I wanted to).": You still have the ability to do it, but you no longer have the opportunity.



But you might still be able to do it today! "I could have done it yesterday" to me, doesn't bring such a strong connotation about today's options as "I could do it yesterday” brings about today's lack of ability/opportunity.

Although the following statement of capability and determination is possible: "I could do it yesterday, I can do it today and I'll bloody well still be able to do it tomorrow."


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## Prower

What would be the difference between

I couldn't do it yesterday.
I couldn't have done it yesterday.


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## chasfh

JulianStuart said:


> But you might still be able to do it today! "I could have done it yesterday" to me, doesn't bring such a strong connotation about today's options as "I could do it yesterday” brings about today's lack of ability/opportunity.
> 
> Although the following statement of capability and determination is possible: "I could do it yesterday, I can do it today and I'll bloody well still be able to do it tomorrow."



I don't think that's most commonly the case, though.  Take your lawnmower example: when you told your mechanic, "I could start it yesterday" -- particularly with emphasis on "start" and "yesterday" -- without saying another word, then you were also strongly implying to him, "but I can't start it today".  You no longer have the ability to do it.  I think that is the most common use of this tense in this type of case.

I guess it all comes down to context, though, doesn't it?  There's no hard and fast here, is there?


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## JulianStuart

I think we agree on that: It may have been a little convoluted, because I was trying to say:  "I could do it yesterday" brings strong connotations about today's lack of opportunity/ability.  The determination example, however, _was_ contrived - i.e. rare!

I almost added a comment on context too.


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## JulianStuart

Prower said:


> What would be the difference between
> 
> I couldn't do it yesterday.
> I couldn't have done it yesterday.



In the first one you tried and failed. 

In the second, you are either explaining to the detective about your alibi (  ) or to the "customer" that you didn't have time (or parts or physical strength or some such excuse  ) to do it yesterday.


All subject to influences of context, for which there is so far none supplied.  The first _could_ mean what the second explanation describes, given the appropriate context.


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## Prower

Thank you very much for the on-going contributions. Could you approve or disapprove the correctness of this conclusion of mine. 

*I could visit my relatives, but I didn't want to go. *
Comment: Am I right to think that this sentence is not correct because as I didn't really visit them I shouldn't use *could visit* instead I should use 

I *could have visited *my relatives, but I didn't want to go.

Because I really didn't go there.

Or is it interchangable?


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## JulianStuart

You are right the first bold sentence "*I could visit my relatives, but I didn't want to go. "* is not correct.  However, it is mainly because of a _tense mismatch_, which you corrected in the second version. 

"*I could have visited my relatives, but I didn't want to go."* Pretty clear that you didn't go.The other correction might be (again, matching the tenses) "*I could visit my relatives, but I don't want to go." *Outcome to be determined


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## Prower

Interesting that you mention the tense mismatch. I thought it was due to the different reason.

If I add yesterday.

*I could visit my relatives yesterday, but I didn't want to go.* - Is it still wrong because of the tense mismatch?


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## JulianStuart

YES!  You would need a time machine to have the ability to_ go_ to visit your relatives yesterday.  "I could have visited my relatives yesterday, but I didn't feel like it."


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## Prower

JulianStuart said:


> YES!  You would need a time machine to have the ability to_ go_ to visit your relatives yesterday.  "I could have visited my relatives yesterday, but I didn't feel like it."


I don't quite understand your reference to a time machine.

If I said - I *can *visit my relatives *yesterday*. - Then I probably would need one.

I understand you are saying that - could do - can't refere to the past. Then what about your example

I could start it yesterday (POST 17) Does it refer to the past?


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## Prower

I don't understand why you think that here is a tense mismatch.

Here it is an example in the past.

When he *told *me about it, I *was *pretty upset, but when he *explained *it to me, I *could *understand. (not could have understood).
============

Why is it a mismatch here? ------ I *could *visit my relatives yesterday, but I *didn't *want to go.


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## JulianStuart

Prower said:


> I don't quite understand your reference to a time machine.
> 
> If I said - I *can *visit my relatives *yesterday*. - Then I probably would need one.
> 
> I understand you are saying that - could do - can't refere to the past. Then what about your example
> 
> I could start it yesterday (POST 17) Does it refer to the past?



"Might choose to" is not the same as "was able to" even though both can use the word "could"

I could start it yesterday = I was able to do it yesterday.
I could visit my relatives yesterday (I was able to yesterday but something is preventing me today).

"I could go out for lunch today" or "I could stay home".  This is _not_ the same form of the word "could".  "I could go out for lunch" does not mean "I can go out for lunch" it means "I might choose to go out for lunch"  and clearly "I could (meaning = might choose to) go out for lunch yesterday" needs a time machine


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## Prower

JulianStuart said:


> "I could go out for lunch today" or "I could stay home".  This is _not_ the same form of the word "could".  "I could go out for lunch" does not mean "I can go out for lunch" it means "I might choose to go out for lunch"  and clearly "I could (meaning = might choose to) go out for lunch yesterday" needs a time machine



I see now. If there are two ways to understand it then why do you choose yours? I mean there must be a reason. I personally saw a different meaning in this setence i.e.

*I could visit my relatives yesterday, but I didn't want to go. = I was able to visit my relatives yesterday, but I didn't want to go.*

So I wonder why you turned down this meaning.


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## Forero

With past tense modals (_could_, _would_, _should_, _might_), it is easy to confuse inherent meaning with meaning gleaned from context.

_Could_ can mean "was able to", "would be able to", "possibly did", or "managed to", among other things, and _could have_ can mean "was able to have", "had been able to", "would have been able to", "possibly had", "was possibly able to", "managed to have", "had managed to", and any number of other things. Which meaning applies has to come from context, and even in context, ambiguities usually remain.

In the original sentence, I think _could have achieved_ is meant as "had been able to achieve". His achievement preceded their wondering about his ability to manage it. _Could achieve_ almost has to mean the same thing in this context, but without the rest of the context, the part beginning with "they wondered" would be quite ambiguous, with possible meanings such as "they wondered how (at that moment) he had the ability to achieve ..." or "they wondered how he might in future achieve ...".


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## Prower

I got so confused by other threads which touch on this subject a bit but don't disclose it in full, that I'd like to make this thread to discuss.

I can see that 

*Could *can refer 1) Present 2) Past
*Could* can mean 1) is able/was able 2) might choose to do something

_What beats me is how to undersatnd when it is said about the present or the past._
=========
Example

*I could take part in this course, but I didn't do it.*


_I am sure_ that a native speaker sees "could" as - I might choose to take part...... Hence the second part of the sentence should be changed to the present.

However, *what hinders* us to see another meaning *here?* where "could" would mean - _was able to_ - I was able to take part in this course but I did't do it.
=======
Do you see my point?


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## JulianStuart

Prower said:


> *I could visit my relatives yesterday, but I didn't want to go. = I was able to visit my relatives yesterday, but I didn't want to go.*
> 
> So I wonder why you turned down this meaning.



I think in the absence of any context, I am likely to make one up based on probablilities!  For the meaning you describe, I think it's very likely that people would prefer the "could have" version to the "could" in your example in bold above.  The more likely narrative after the trip yesterday would be "I (was able to and) might have chosen to visit but didn't want to" and the less likely "I had the opportunity to visit yesterday and chose not to, but today I am unable to".


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## chamyto

I think it´s the same as the present .

abilities = I could swim 3 miles away when I was a child , but now I can´t (~ be able to )


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## JulianStuart

Try this:  If the meaning is "might choose to", then the tenses must match.

If the meaning is "am/was able to" then _could_ could mean either _am able_ or _was able_ 

Perhaps this simplification is over-reaching, but in the absence of any hints from context, let's see what other native speakers and professionals have to add or modify.


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## chasfh

Prower said:


> =========
> Example
> 
> *I could take part in this course, but I didn't do it.*
> 
> 
> _I am sure_ that a native speaker sees "could" as - I might choose to take part...... Hence the second part of the sentence should be changed to the present.
> 
> However, *what hinders* us to see another meaning *here?* where "could" would mean - _was able to_ - I was able to take part in this course but I did't do it.
> =======
> Do you see my point?



The phrase above mixes two timeframes, starting out with the present in the first part, but ending with the past in the second part.  The two parts need to agree.

If you're talking about the present, "could" works by itself:

*I could take part in this course, but I'm not doing so.*

If you're talking about the past, "could" needs to become "could have":

*I could have taken part in this course, but I didn't do so.*

Note, too, how I changed "it" to "so" at the end, because it sounds better to my American ears.

Does that get you any closer?


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## panjandrum

_<< Moderator note.
The three threads on this topic that were active in the forum yesterday have now been merged.
The resulting thread has been checked for continuity - to make sure that the connection between posts is clear - and __quoted versions of earlier posts have  been inserted __in a small number of posts.  All changes are clearly marked.
I hope we all don't find the outcome confusing ... at least in terms of the flow of the discussion 

panjandrum >>
_


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## panjandrum

Having done that, I'm seizing the opportunity to respond to a couple of points raised earlier 


Prower said:


> Thank you panjandrum
> 
> Seems like you have understood my concern 100%.
> 
> 
> However a new question is on the way as it is a natural continuation in this case.
> 
> You have given the same explanation to these two.
> 
> Seems like they are the same. Are they?
> 
> I couldn't do it yesterday.
> I couldn't have done it yesterday.


I included in my explanations the aspects of the meaning that were important to the question at that point.
There is an additional aspect of meaning: the basis on which I might say one of these.

This relates to a comments I made earlier, post #12, about 
"I could do it yesterday."
_>> I know that I was able to do it yesterday because I did it._
I could have done it yesterday.
_>> I could have done it yesterday (but perhaps I wasn't asked).         _

The red sentences relate conclusions based on evidence from yesterday.
The ability to do it, the opportunity to do it, were tested yesterday.

The blue sentences relate opinions based on my analysis today.
The ability to do it, the opportunity to do it, were not tested yesterday.




Prower said:


> I got so confused by other threads which touch on this subject a bit but don't disclose it in full, that I'd like to make this thread to discuss.
> 
> I can see that
> 
> *Could *can refer 1) Present 2) Past
> *Could* can mean 1) is able/was able 2) might choose to do something
> 
> _What beats me is how to undersatnd when it is said about the present or the past._
> =========
> Example
> 
> *I could take part in this course, but I didn't do it.*
> 
> 
> _I am sure_ that a native speaker sees "could" as - I might choose to take part...... Hence the second part of the sentence should be changed to the present.
> 
> However, *what hinders* us to see another meaning *here?* where "could" would mean - _was able to_ - I was able to take part in this course but I did't do it.
> =======
> Do you see my point?


What hinders us is the explanation above.
For "I could take part in this course," to be valid in reference to the past, it would have to have been tested and proven true.
So "I could take part in this course, but I didn't," is a contradiction.
_
I could take part in this course, so I did._
Clearly talking about past ability, realised.
_
I could take part in this course, but I don't really want to._
Clearly talking about current ability that may or may not be realised.

This is true for me with this example.


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## newname

panjandrum said:


> What hinders us is the explanation above.
> For "I could take part in this course," to be valid in reference to the past, it would have to have been tested and proven true.
> So "I could take part in this course, but I didn't," is a contradiction.
> _
> I could take part in this course, so I did._
> Clearly talking about past ability, realised.
> _
> I could take part in this course, but I don't really want to._
> Clearly talking about current ability that may or may not be realised.
> 
> This is true for me with this example.



I think what really hinders us is this rule: (Practical Engish Grammar by Thomson)
 1. For ability only, either COULD or WAS/WERE ABLE can be used
 When I was young, I could/was able to climb any tree in the forest.
2. For ability + particular action, use WAS/WERE ABLE
 The boat capsized near the bank so the children were able to swim to safety. (They could and did swim)

The 'could + perfect infinitive' is used to express
 3. possibility (It's equivalent to may/might + perfect infinitive)
 I wonder how he knew about her marriage? ~ he might/may/could have heard from Jack.
 4. past ability when the action was not performed or when we don't know whether it was performed or not.
 Son: I could have taken part in this course, but I didn't. 
 Dad:  You fool! You should have told me. (or You fool! you could have told  me. ##This is the second use of 'could + perfect infinitive' to express  irritation at or repproach for the non-performance of an action) 

From the mentioned rules, I would thus say,

The sentence 'I could take part in this course, but I did not do it' really falls into this number #2, i,e I could and I took action according to my wish.
I do not know if this rule has been relaxed recently. If it has not, then we must say,
 I was able to take part in this course, but I didn't. 
and even with 'was able' I don't think it (this particular sentence) is logically grammatical.


##############################
As  for the 'can/could not + perfect infinitive' structure, no discussion  on it should continue because it is the opposite of the must + perfect  infinitive, ie they are negative deductions about past events. Any good  grammar book should have a section for it.


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## Prower

panjandrum said:


> For "I could take part in this course," to be valid in reference to the past, *it would have to have been tested and proven true.*
> So "I could take part in this course, but I didn't," is a contradiction.


It seems to me that this is not only a grammar issue but a logical one as well. I am just somehow not so categorical in interpreting this situation that way. 

==========
- Before you can take part in this course your physical abilities are to be tested and proven true to fit for this course. This is why we shall conduct a few tests and check-ups to see if you fit.

Later on.

- Great! They told me I can take part in this course here it is the certificate (or whatsoever). But I don't want to anymore. So I won't take part.
=========

This scenario is quite possible.


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## Prower

newname said:


> 4. past ability when the action was not performed or when *we don't know whether it was performed or not.*
> Son: *I could have taken part* in this course, but I didn't.
> Dad:  You fool! You should have told me. (or You fool! you could have told  me. ##This is the second use of 'could + perfect infinitive' to express  irritation at or repproach for the non-performance of an action)


Well, I think the speaker should know whether he took part or he didn't. So I think this rule should apply when a speaker is in first person.


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## newname

Prower,

I think the could do version expresses a past ability, thus:
- I could take part in the course, but I didn't = I had the ability but I didn't.
The could have done version expresses past possibilty, thus:
- Why didn't you take part?
  I could have, but I didn't.(= it was possible for me to do so, but I didn't)

P.S
At least, the could have done structure is an equivalent of might/may have done structure according to my grammar book.


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## panjandrum

Prower said:


> Originally Posted by *panjandrum*
> 
> For "I could take part in this course," to be valid in reference to the  past, *it would have to have been tested and proven true.*
> So "I could take part in this course, but I didn't," is a contradiction.
> 
> 
> 
> ...
> ==========
> - Before you can take part in this course your physical abilities are to be tested and proven true to fit for this course. This is why we shall conduct a few tests and check-ups to see if you fit.
> 
> Later on.
> 
> - Great! They told me I can take part in this course here it is the certificate (or whatsoever). But I don't want to anymore. So I won't take part.
> =========
> 
> This scenario is quite possible.
Click to expand...

Perhaps, but that is not relevant to the point I made earlier.  Your scenario is specifically relating to the present - can - don't - won't.
The scenario I talked about related to a possibility that was acted on in the past


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## Prower

newname said:


> Prower,
> 
> I think the could do version expresses a past ability, thus:
> - I could take part in the course, but I didn't = I had the ability but I didn't.



If you go through this thread again you will see that the issue here is not the meaning of this sentence which you say it has, but the issue is that this sentence is wrong. This is what I have been trying to find out why, and it seems to me that I have understood why.


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## Prower

panjandrum said:


> Perhaps, but that is not relevant to the point I made earlier.  Your scenario is specifically relating to the present - can - don't - won't.
> The scenario I talked about related to a possibility that was acted on in the past


I think you misunderstood me. This dialog took place in the PAST. 

The person says this "I could take part in this course but I didn't want to" after this dialog.


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## panjandrum

This is what you wrote.


Prower said:


> ...
> - Great! They told me I can take part in this course here it is the certificate (or whatsoever). But I don't wantto anymore. So I won't takepart.
> ...
> This scenario is quite possible.


I agree, that scenario is quite possible.  But the red words are present, not past.


Prower said:


> I think you misunderstood me. This dialog took place in the PAST.
> The person says this "I could take part in this course but I didn't want to" after this dialog.


I didn't misunderstand you.  You left out this important piece of information.

You can speak about a present possibility and a current response:
_I could take part in this course but I don't want to._
- or -
You can speak about a past possibility and a past response:
_I could have taken part in this course but I didn't want to._

You can't mix them.

As it is clear that I am not able to convince you of this, I withdraw from the thread.


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## Prower

panjandrum, wait a minute. Believe it or not but I understood why it doesn't work. You have also made an input into this. To be more sepcific why *this sentence* doesn't work

*I could take part in this course but I didn't do it.*

I think you still misunderstand my example with dialog. I just described the prestory which led this guy to say *the next day* - I could take part in this course but I didn't want to.

I am still struggling with this one

*I could take part in this course but I didn't want to.*
Because I think willingess and ability may go different ways. This is why I don't see why someone can't do something not willing to.

I was able to do it (and I did it) but I didn't want to do it = I could do it but I didn't want to.


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## Yichen

1. I could buy the bike yesterday if had enough money.
2. I could buy the bike today if had enough money.
3. I could buy the bike tomorrow if had enough money.

Is sentence 1 correct?


Thank you.


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## Cagey

It depends on what you mean, but I don't think this is correct. 


> 1. I could buy the bike yesterday if I had enough money.


(You are missing the subject '_I_' in the second clause of all these sentences. )

When you are talking about something that wasn't possible in the past, this becomes an unreal condition.  
1._ I could have bought the bike yesterday if I had had enough money._

Is that what you have in mind, or do you want to say something else?  Please explain the situation using other words.


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