could, only for a temporary ability?

[keannu]

Is it true that could can't be used for a past one time ability but only for a usual ability? Doesn't could make sense in the following? I think I've heard such use while listening.

ex)It was very hot last night, but we were able to have(could) a good sleep thanks to the air conditioner.

 

[Raymott]

Is it true that could can't be used for a past one time ability but only for a usual ability? Doesn't could make sense in the following? I think I've heard such use while listening.

ex)It was very hot last night, but we were able to have(could) a good sleep thanks to the air conditioner.

Yes, it is possible. I'd write: " ... but we found we could sleep if we had the air conditioner on." You could write simply " ... but we could sleep thanks to the air conditioner." This second version doesn't suggest a one-time event though. It implies they already knew they could sleep with the air conditioner. My example does suggest a one time experience.

"I had trouble escaping from prison, but after I had fasted for a month, I could just squeeze through the bars. One time in the past - OK.

 

[Verona_82]

Raymott, you've just undermined my grammar knowledge! Up until now I've been sure 'could' doesn't work for one time experiences in the past. Now I see it does...

 

[Raymott]

Raymott, you've just undermined my grammar knowledge!

Sorry about that. I can't promise I won't do it again though. ;-)

 

[Khosro]

Sorry about that. I can't promise I won't do it again though. ;-)

Raymott! Before my grammar knowledge gets undermined as well, I want to ask for your opinion if the use of "could" in your example has anything to do with the "just" after it, I mean with the negative implication of the sentence.

 

[5jj]

Up until now I've been sure 'could' doesn't work for one time experiences in the past. Now I see it does...

Raymott selected examples where it does work. There are, however, many sentences in which only was/were able to works. I would recommend that you go with what you have always believed; you won't produce unacceptable sentences.

 

[Raymott]

Raymott! Before my grammar knowledge gets undermined as well, I want to ask for your opinion if the use of "could" in your example has anything to do with the "just" after it, I mean with the negative implication of the sentence.

No, the 'just' isn't necessary.

 

[keannu]

Raymott selected examples where it does work. There are, however, many sentences in which only was/were able to works. I would recommend that you go with what you have always believed; you won't produce unacceptable sentences.

Can you explain when to use could and when to use be able to?
It's hard to distinguish the two, and I've never thought about it so far, but happened to find the difference in my grammar book, which really surprised me.

 

[5jj]

Can you explain when to use could and when to use be able to? It's hard to distinguish the two...

Most grammarians agree that modals are 'messy' - it is impossible to define the meanings precisely and simply.

Very crudely, when we are talking about situations in the past could means 'had the possibility/ability to', and was/were able to means 'had the possibility to and did'.

At the age of ten, Peter could speak three languages fluently. Presumably did speak them, but we are told only that he knew how to.

About six months after we moved back to England, a French family with a child of my own age moved into the house next door, so I was able to speak French again. Presumably he had the ability all the time, but not the opportunity, until the family arrived; then he did speak French again.

In the negative form, the difference is not so important, because the activity did not happen.

:tick: I was able to get back to England in time for the birth of our child.
X(?) I could get back to England in time for the birth of our child.
:tick:I couldn't/wasn't able to get back to ngland in time for the birth of our child.

When the context makes it absolutely clear that the activity did take place, then it is possible to use could when we might expect was able to, as Raymott has shown. Even in these situations, a listener might ask, "But did he/they actually do it, then?" The learner is safer using was able to.

That is my opinion.

 

[keannu]

Most grammarians agree that modals are 'messy' - it is impossible to define the meanings precisely and simply.

Very crudely, when we are talking about situations in the past could means 'had the possibility/ability to', and was/were able to means 'had the possibility to and did'.

At the age of ten, Peter could speak three languages fluently. Presumably did speak them, but we are told only that he knew how to.

About six months after we moved back to England, a French family with a child of my own age moved into the house next door, so I was able to speak French again. Presumably he had the ability all the time, but not the opportunity, until the family arrived; then he did speak French again.

In the negative form, the difference is not so important, because the activity did not happen.

:tick: I was able to get back to England in time for the birth of our child.
X(?) I could get back to England in time for the birth of our child.
:tick:I couldn't/wasn't able to get back to ngland in time for the birth of our child.

When the context makes it absolutely clear that the activity did take place, then it is possible to use could when we might expect was able to, as Raymott has shown. Even in these situations, a listener might ask, "But did he/they actually do it, then?" The learner is safer using was able to.

That is my opinion.

Thanks a lot for your detailed explanation, and Raymott's following example seems to imply it's a one-time experience as the front part back up he couldn't help but do it due to the long preparation and effort.
"I had trouble escaping from prison, but after I had fasted for a month, I could just squeeze through the bars. One time in the past - OK

I really feel ashamed of my numerous expressions of "could" meaning one-time event, so were they all grammatically incorrect(maybe not), but the listeners could understand my expressions(again, could for one-time..)
I've said like these so many times..
"I could meet someone at a specific place at a specific place"
"I could call him at 2pm, I could do it (specific moment)"
I don't think it will be easy for me to convert all of them to "be able to"....

 

[Khosro]

Thanks a lot for your detailed explanation, and Raymott's following example seems to imply it's a one-time experience as the front part back up he couldn't help but do it due to the long preparation and effort.
"I had trouble escaping from prison, but after I had fasted for a month, I could just squeeze through the bars. One time in the past - OK

I really feel ashamed of my numerous expressions of "could" meaning one-time event, so were they all grammatically incorrect(maybe not), but the listeners could understand my expressions(again, could for one-time..)
I've said like these so many times..
"I could meet someone at a specific place at a specific place"
"I could call him at 2pm, I could do it (specific moment)"
I don't think it will be easy for me to convert all of them to "be able to"....

What kind of one time exprience? An exprience of ability or an exprience of ability and doing something? These are different as we see from fivejedjon's post. If you find it hard to convert all of those sentences to "be able to" sentences then perhaps you should ask yourself what you really mean by them. Just ability? Or ability and action together?

I had the same problem with "could" some years ago and yesterday I realized that still I have problems with it (so far I thought that "could" and "be able to" convey the same meaning). At that time I found a solution for it: Whenever I wanted to refer to having the ability to do something and doing it as well in the past I used verbs such as "succeed" and "managed". I will try to find out how people really use "be able to" in such cases.