# be able to do vs could do vs could have done



## Angelya

Hi, all! If I want to say "Jack was able to do better than John", can I rephrase it as "Jack could do better than John" or "Jack could have done better than John". Which one is right? Or are they both acceptable?


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## owlman5

Hi.  If Jack actually did something better than John did it, you would do better to say "Jack was better than John was at something."  Or: "Jack did something better than John did it."

If you are _guessing_ that Jack could have done something better than John did it, it would make sense to say "Jack could have done better than John."  That phrasing would make it clear to me that you were giving an _opinion_ rather than stating a _fact_.


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## anthox

"Jack could do better than John" -> In general, or at some future time.
"Jack could have done better than John." -> At that particular time in the past/in the particular situation in the past.


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## Jimbob_Disco

'Jack could do better than John'  - the tense is now wrong
'Jack could have done better than John'


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## Angelya

So, it doesn't make sense to say "I thought Jack could do better than John". "I thought Jack could have done better than John" is right. To my understanding, however, there are three understandings of this sentence. One is that I thought Jack was able to do better than John while the other is that I thought Jack was able to do better than John but actually he didn't. And also, I thought Jack may have done better than John. So, what do you think? Looking forward to your replies!


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## Steven David

Angelya said:


> Hi, all! If I want to say "Jack was able to do better than John", can I rephrase it as "Jack could do better than John" or "Jack could have done better than John". Which one is right? Or are they both acceptable?



All three are correct. This is a question what they mean.




Angelya said:


> If I want to say "Jack was able to do better than John", can I rephrase it as "Jack could do better than John" or "Jack could have done better than John".



No, you cannot use "Jack could do better than John" or "Jack could have done better than John" *in place of *"Jack was able to do better than John" because they have different meanings.

__________________________

1) "Jack was able to do better than John."  << This means, "Jack had the ability to do better than John, and now Jack does not have the ability to do better than John.

2) "Jack could do better than John." << This means, "It's *possible *that Jack can do better than John." This is a reference to present or future.

3) "Jack could have done better than John" << This has two means depending on context:

A) It's possible that Jack did better than John. But we don't know whether this is true or not. This speaks of something in the past.

B) Jack did not do better than John. The possibility existed for Jack to do better than John. However, Jack did not succeed in doing better than John.

_________________________

Note:

2) "Jack could always do better than John." << If we add "always" to this sentence, then we understand that this is a reference to the past: it's past time.

So with "always", this sentence means 1) Jack was always able to do better than John, and now Jack is *not *able to better than John. 2) Jack has always been able to do better than John, and Jack *is still* able to do better than John.

_________________________


Context always automatically tells people which meaning to apply in any case in which more than one meaning is possible.

As for which one to choose, then we have to know, and consider, the meaning of each one of your example sentences.


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## Steven David

Angelya said:


> I thought Jack may have done better than John.



Speaking of "Jack may have done better than John" 

This means, "It's possible that Jack did better than John, but we do not know whether or not this is true. 

Using "may have done" communicates a stronger possibility. Using "could" communicates a neutral possibility. 

Using "might have done" communicates a weaker possibility. 

Comparing "might, may, and could" in speaking of possibility is another topic.


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## Angelya

Thanks for your replies! Let me give you another situation. Suppose there was a stone which a boy needed to do something. But he found it really ugly and decided not to take it. Because on the river bank nearby where were many beautiful and smooth stones, he (could have found/could find/could always find) a much better one . According to your replies,  I think "could have found" and "could always find" are correct here to show the capability of the boy to find a better stone. Judging from Steven's answers, "could have done" can show a possibility in the past. And in my view, possibility has two meanings, one is capability while the other is likelihood. I don't know whether it's right. In China, we distinguish these two concepts. We don't call something that can be made or is able to be done a possibilty. Having been staying in this forum, I believe native speakers have different understanding of it. You seem to call such a case a possibility, too! Am I right on this? That's why I think "could have found" and "could always find" are both correct in my new sentence. What do you think? I figure your replies will definitely give me a better understanding of "could have done" on its usage of ability and likelihood. Looking forward to your replies!


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## Steven David

Angelya said:


> Thanks for your replies! Let me give you another situation. Suppose there was a stone which a boy needed to do something. But he found it really ugly and decided not to take it. Because on the river bank nearby where were many beautiful and smooth stones, he (could have found/could find/could always find) a much better one . According to your replies,  I think "could have found" and "could always find" are correct here to show the capability of the boy to find a better stone.



If the boy chooses another stone in that moment then we could say this:

He didn't choose the ugly stone, the first stone he found, because he knew he could find a better stone.

If the boy leaves the riverbank and decides not to look for another stone, then we can say this:

He could have found a better stone, but he decided to leave and come back the next day to search for another stone.

If the boy chose to take the stone that he didn't like, then we can say this:

He could have found a better stone, but he decided to take the first one that he found.

The last sentence means that it was possible for him to find a better stone, but he chose not to.

This is also possible:

He decided to take the first stone that he found because he knew he could always go back and find another stone.

In that moment, he would think this:

I can always return and find another stone.


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## Angelya

Steven David said:


> If the boy chooses another stone in that moment then we could say this:
> 
> He didn't choose the ugly stone, the first stone he found, because he knew he could find a better stone.
> 
> If the boy leaves the riverbank and decides not to look for another stone, then we can say this:
> 
> He could have found a better stone, but he decided to leave and come back the next day to search for another stone.
> 
> If the boys chose to take the stone that he didn't like, then we can say this:
> 
> He could have found a better stone, but he decided to take the first one that he found.
> 
> The last sentence means that it was possible for him to find a better stone, but he chose not to.
> 
> This is also possible:
> 
> He decided to take the first stone that he found because he knew he could always go back and find another stone.
> 
> In that moment, he would think this:
> 
> I can always return and find another stone.


I really appreciate your help! But I still need more help... I remember you have told me "could do" is a reference to the present and future. How does it work in "He didn't choose the ugly stone, the first stone he found, because he knew he could find a better stone"? And what I want to say is that the boy was able to pick up a better stone but we are not sure whether he actually picked up one. So, does the sentence still work in this situation? It's really so confusing to me! Would you please offer more help?


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## Steven David

Angelya said:


> I really appreciate your help! But I still need more help... I remember you have told me "could do" is a reference to the present and future. How does it work in "He didn't choose the ugly stone, the first stone he found, because he knew he could find a better stone"? And what I want to say is that the boy was able to pick up a better stone but we are not sure whether he actually picked up one. So, does the sentence still work in this situation? It's really so confusing to me! Would you please offer more help?



To use "could" to refer to the present or future, the boy could think or say this:

I'm not going to take this stone. I could find a better stone (now or later on).

In the above example, "could" speaks of an open possibility for the present and the future.

It's also possible to use "can" in the above example. With "can", we speak of ability in the present or the future.

"He knew he could find a better stone." << He knew it was possible then, in that moment, he knows it's possible in the present, and he knows it's possible in the future.

That moment, when he's at the riverbank, is a present moment for him. And he can think "could" in that present moment, which later becomes the past, of course.

___________________

The boy was able to pick up a better stone, but we are not sure whether or not he did.

To express this idea, we use "could have done".

He could have picked up a better stone.

He could have found another stone.

Why why has he been at the riverbank for so long? He's been there for a few hours.

I don't know. He could have been searching for another stone.

Didn't he say that he already found one?

Yes, he did, but I don't think he liked it very much. And I think he could have been searching for another one. *He could have found another stone by now. *Who knows? Let's call him and find out.


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## Steven David

Here's another situation in which we do not know whether or not he could have found a better stone.

I decided to take this stone. It's not really the best one, but I decided to take this one, anyway. It'll serve the purpose.

Do you think you could have found a better stone?

Maybe. I don't know. *I suppose I could have found a better stone*, but I didn't think it was worth the time because this one is going to serve the purpose very well.

I think you should have kept looking for another stone.

Get serious, will you? It's not like I have 10 hours to spend looking around for a better stone at the riverbank.

You're exaggerating. It could not have taken 10 hours to find another stone.

The last sentence means that it was not possible for it to take 10 hours find another stone.


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## Steven David

Addition to a previous post:

2) "Jack could always do better than John." << If we add "always" to this sentence, then we understand that this is a reference to the past: it's past time.

The above sentence is a reference to the past, as I said.

However, it could refer to the future, as well. We have to add a little context or change the context a little bit.

Jack's golf game has improved a lot. But he could always do better if he practiced more.

So the big takeaway is that modal verb "could" can be a reference to the past, the present, or the future. It all depends on context and speaker viewpoint.


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## Eric Chengdu

Hi Steven, I can't wait to give your answer a big thumbs-up Many people including me have asked the simlar questions about "could have ppt" more times than I can count, which is really a headache for "english as a second language" learners. I have also read many answers trying to explain this in almost any way. Now, without any doubt, I have to say your answer is the best I have ever seen, which couldn't be better and clearer. It's really worth us reading over and over, savouring every word.


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## Steven David

You're welcome, Eric. And thank you for saying so.


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## Steven David

One more thing comes to mind that I should add.

Could speaks of possibility. Could also has to do with ability. However, the emphasis is on possibility with could.

Can speaks of ability. Can also has to do with possibility. However, the emphasis is on ability with can.


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## Steven David

Here's something else that's interesting.

Although "could have done" is a reference to the past, "have done" is still a reference to the present.

So "could have done" really means that it was possible for someone to do something and this remains relevant until now.

No matter how long ago it was possible for someone to do something, saying "X could have done Y" is like saying "this thing that was possible in the past is relevant up until now".

So "could have done" is a perfective or perfect modal. It brings possibilities from the past up to the present just like present perfect tells us that past actions are relevant up until now - the present. That's what we can say "perfect" means: complete up until now. Nothing is ever really perfect, though, is it? No, nothing is ever perfect. Something can only be complete up until now. Perfection is a continuous and never-ending process.


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## Shooting Stars

Steven David said:


> 1) "Jack was able to do better than John." << This means, "Jack had the ability to do better than John, and now Jack does not have the ability to do better than John.





Steven David said:


> The boy was able to pick up a better stone, but we are not sure whether or not he did.


"
According to these two explanations, "was able to do something" means had the ability to do something.

But an English book said if somebody was able to do something, he not only had the ability to do it, but also managed to do it. It gave an example.
Although the pilot was badly hurt he was able to explain what had happened. (He could and did explain.)
The explanation in brackets is of the book.
It appears there is a little difference between the two explanations. I am a little confused. What is meant by "was able to do something"?

Thank you.


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## owlman5

If you *are able *to do something, you have *enough skill/knowledge/etc. to do it *without any further preparation.  It is another way to say that you *can* do something.


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## Steven David

Shooting Stars said:


> "
> According to these two explanations, "was able to do something" means had the ability to do something.
> 
> But an English book said if somebody was able to do something, he not only had the ability to do it, but also managed to do it. It gave an example.
> Although the pilot was badly hurt he was able to explain what had happened. (He could and did explain.)
> 
> The explanation in brackets is of the book.
> 
> It appears there is a little difference between the two explanations. I am a little confused. What is meant by "was able to do something"?
> 
> Thank you.



*But an English book said if somebody was able to do something, he not only had the ability to do it, but also managed to do it. * << It is true that we can understand and use "be able to" in this way. However, there's some overlap with the two ideas. Sometimes it seems that only "be able to" is possible. And other times it is possible to use "can" or "could" in place of "be able to".


*Although the pilot was badly hurt, he was able to explain what had happened. (He could and did explain.) <<* Yes, you are correct. It is possible to use "could" in place of "was able to" here. If we use "was able to", we get the idea, more readily, that "explaining was difficult, and he overcame this difficulty". The general idea is "obstacle". With "be able to", we often get the idea there was some sort of obstacle, which then also gives us the idea of "manage to".

*It appears there is a little difference between the two explanations. I am a little confused. What is meant by "was able to do something"?* <<

It's a question of where we place our focus or emphasis. Yes, "be able to" indicates that there is some difficulty or obstacle to overcome, and so we can think of "be able to" as "manage to do something". Again, we have to consider context. Sometimes we can use "can" and "could" instead of "be able to". There would not be direct focus on the idea of "managing to do something" or overcoming an obstacle. However, context may tell us that someone, or something, "manages to do something" or "overcomes an obstacle".

Grammar books do not account for everything that is possible in native speaker speech.

Suggestion:

Listen, read, and analyze. When you come across "can", "could" and "be able to", ask yourself why you think the speaker or writer uses one of them.

I suggest taking your study outside of grammar books. It seems that you have the understanding, knowledge, and analytical skills to do this. You notice inconsistencies, which is very good. So you can notice and observe language based on your current knowledge of English.

You are able to do this. < Despite any difficulty that may present itself, you have the ability  to do this.

You can do this. < You have the ability to do this.

Think of "able" as being a separate word from "be able to". The word "able" is an adjective. We use "able" to describe someone with ability.

There's an expression: Ready, willing, and able.

The idea with this expression is that one is able to do something despite any difficulty, or obstacle, that makes it more challenging.


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## Angelya

I really appreciate your clear explanations! You have helped me a lot! You know, this question has been on my mind for quite a long time. Though I have asked about it, the answers I got only covered part of usage of "could have done" and every time I came across a new usage I wasn't just sure whether it's right or not. Many thanks! And as you have suggested, I have been taking my study out of grammar books because I think they can't cover the full contents of language. Language is flexible and changing. Everyday there may be new words appearing and old rules being broken. English is lively, so I just discover the phenomenon and learn and remember. In conclusion, I'm very grateful for everyone helping me and other language learners!


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## Angelya

Sorry, another situation came to my mind! 
"I can draw a picture of my mom!" said the boy. If we change it to an indirect speech, is it "the boy said he could draw a picture of his mom" or "the boy said could have drawn a picture of his mom"?


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## Steven David

Angelya said:


> Sorry, another situation came to my mind!
> "I can draw a picture of my mom!" said the boy. If we change it to an indirect speech, is it "the boy said he could draw a picture of his mom" or "the boy said could have drawn a picture of his mom"?




The boy says now, "I can draw a picture of my mom."

What did he say? Indirect speech for this is, "The boy said he could draw a picture of his mom."

____________

Direct speech: The boy says now, "I could have drawn a picture of my mom."

Indirect speech: What did the boy say? He said he could have drawn a picture of his mom.


So in the last example above, we see that "could have done" is indirect speech for "could have done". It does not change in this way.

"I could have drawn a picture of my mom." That's what he said at first, and that's how we repeat or recognize what he said later on. 

Indirect speech: What did he say? "He said that he could have drawn a picture of his mom."

Direct speech: What did the boy say -- his exact words? He said, "I could have drawn a picture of my mom."


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## Steven David

Only recognizing the possibility, not his ability, the boy says this:

I could draw a picture of my mom. Maybe, I will. I don't know yet. -- Note that this use of "could" is a reference to the present or future. It's a possibility now, for the future, or both present and future.

Indirect speech for the above statement - What did the boy say? He said he could draw a picture of his mom and that, maybe, he will, but he does not know yet."

Direct speech: What did the boy say - his exact words? He said, "I could draw a picture of my mom. Maybe, I will. I don't know yet."

_____

Here's another idea, and this really highlights the essence of "could" and "can".

*Could is more distant. *Could represents distance in time, possibility, and social distance: formality or politeness.

I could make some tea, if you want. - Possibility

I couldn't make coffee, so I made tea. - Past time

Could you make some tea for me? - Social distance - politeness.


*Can is closer.* Can represents closeness in time, possibility, and in a social context. 

I can make some tea, if you want. - Ability - This is possibility, too, but with emphasis on ability. It's stronger than saying "could".

I can't make coffee, I'm going to make tea. - Present time

Can you make some tea for me? - Social closeness - This does not mean that "can" impolite. It just means that "could" a gentler and more polite request. In fact, I would say that "can", with a request like this, is more common than "could".

In unfamiliar circumstances, we might be more inclined to use "could" for a request, but not necessarily. It just depends on context, who's speaking, who's listening, and the environment.


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## Steven David

Another note about context. 

Only recognizing the possibility, not his ability, the boy says this:

I could draw a picture of my mom. Maybe, I will. I don't know yet. -- Note that this use of "could" is a reference to the present or future. It's a possibility now, for the future, or both present and future.

If we remove, "Maybe, I will. I don't know yet", context can tell us that "I could draw a picture of my mom" still means possibility with a reference to the present or the future. 

Tone of voice, the specific way he says this, and what came before in the dialog are enough to let us know that this is a possibility for present or future time. 

I could draw a picture of my mom.  -- Possibility now, at present, and later, future time


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## Angelya

Thanks a million! But I want to use "I could draw a picture of my mom" to show a kind of ability. Then, how does the indirect speech go?


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## Eric Chengdu

Steven David said:


> So "could have done" is a perfective or perfect modal. It brings possibilities from the past up to the present just like present perfect tells us that past actions are relevant up until now - the present. That's what we can say "perfect" means: complete up until now. Nothing is ever really perfect, though, is it? No, nothing is ever perfect. Something can only be complete up until now. Perfection is a continuous and never-ending process.


I like the way you write, explain things, which makes us to see things from a different, unique perspective, otherwise we couldn't possibly do ( you might not have realized your words have such power or how powerful, inspirational they are). I always thought "could have been" was a past tense of "could", I never thought it'd have anything to do with "perfect". the reason why I thought it's less of a "perfect" was I only used it to talk about possibility in past.

a) It seems it's more like a "past tense" than a "perfect" when we're talking about the possibliltiy in the past
We say: I couldn't have imagined that he would be a millionair *one year ago*. (kind of a past tense, I think)
We say: It was impossible for me to imagine *one year ago* that he would be a millionair. (standard past tense)
But we don't say: we haven't thought about that *one year ago*. (because present perfect never ends with something like "one year ago","in 1992" ...)

b) whereas it's more like a "perfect" when we're talking about the possiblitiy in the present
We could have been earning a salary which would help to pay off our debts. (like you said, it was possible for someone to do something and *this remains relevant until now.*)


Angelya said:


> I want to use "I could draw a picture of my mom" to show a kind of ability. Then, how does the indirect speech go?


I'd say" the boy said he was able to draw a picture of his mom".


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## Steven David

Thank you, Eric. I'm glad my replies and explanations help you understand this better.


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## Steven David

Angelya said:


> Thanks a million! But I want to use "I could draw a picture of my mom" to show a kind of ability. Then, how does the indirect speech go?



You're welcome.

We can understand ability with "could" and "was able to" for indirect speech.

As "can" can tell us ability in the present, "could" can tell us ability in the past when speaking of what someone said.

He said he was able to draw a picture of his mom.

He said he could draw a picture of his mom.

It is possible to say that "was able to" tells us he had to learn how to do this, and it was difficult to learn. So, maybe, that's the obstacle or difficulty he had to overcome before being able to draw a picture of his mom.

Using "could" tells us ability in the past or ability spoken of in the past.

It's not that one is absolutely correct all the time for one particular purpose, and the other is not correct. Speaker viewpoint in the moment and in context determines which one a speaker automatically chooses to say.

Using "could" does not focus our attention on overcoming an obstacle in the same way that "was able to" does. However, it is possible to infer that the same thing applies to "could" as it does to "was able to" in speaking of overcoming an obstacle or a difficulty. Logically, we understand that it's not easy to learn how to draw. Or, at least, it's not easy to learn to draw if you want to draw very well and be very skillful.

Having said this, I would have to say that grammar books are correct in pointing out that "be able to" refers to overcoming an obstacle or a difficulty in order to do something or have the ability to do something. However, I have to say the manner in which grammar books explain this seems to be too simple and, at least, a bit crude.

___________________

Years ago, he was able to draw a picture of his mom. Now he doesn't draw as well as he used to.

Years ago, he could draw a picture of his mom. Now he's doesn't draw as well as he used to.

Both of these are correct to speak of ability in the past. Any ambiguity with "could" for possibility in the present and the future is removed with the time phrase "years ago" and the time word "now", which starts the next sentence. Even without the time phrase "years ago", it's still possible to understand that this is "could" for ability in the past, not "could" for present or future possibility. The general context would tell us this. Among other things, the context would include what came before in the dialogue and shared information or knowledge.


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## Angelya

Steven David said:


> You're welcome.
> 
> We can understand ability with "could" and "was able to" for indirect speech.
> 
> As "can" can tell us ability in the present, "could" can tell us ability in the past when speaking of what someone said.
> 
> He said he was able to draw a picture of his mom.
> 
> He said he could draw a picture of his mom.
> 
> It is possible to say that "was able to" tells us he had to learn how to do this and it was difficult to learn. So, maybe, that's the obstacle or difficulty he had to overcome before being able to draw a picture of his mom.
> 
> Using "could" tells us ability in the past or ability spoken of in the past.
> 
> It's not that one is absolutely correct all the time for one particular purpose, and the other is not correct. Speaker viewpoint in the moment and in context determines which one a speaker automatically chooses to say.
> 
> Using "could" does not focus our attention on overcoming an obstacle in the same way that "was able to" does. However, it is possible to infer that the same thing applies to "could" as it does to "was able to" in speaking of overcoming an obstacle or a difficulty. Logically, we understand that it's not easy to learn how to draw. Or, at least, it's not easy to learn to draw if you want to draw very well and be very skillful.
> 
> Having said this, I would have to say that grammar books are correct in pointing out that "be able to" refers to overcoming an obstacle or a difficulty in order to do something or have the ability to do something. However, I have to say the manner in which grammar books explain this seems to be too simple and, at least, a bit crude.
> 
> ___________________
> 
> Years ago, he was able to draw a picture of his mom. Now he doesn't draw as well as he used to.
> 
> Years ago, he could draw a picture of his mom. Now he's doesn't draw as well as he used to.
> 
> Both of these are correct to speak of ability in the past. Any ambiguity with "could" for possibility in the present and the future is removed with the time phrase "years ago" and the time word "now", which starts the next sentence. Even without the time phrase "years ago", it's still possible to understand that this is "could" for ability in the past, not "could" for present or future possibility. The general context would tell us this. Among other things, the context would include what came before in the dialogue and shared information or knowledge.


Then does "He said he could have drawn a picture of his mom" work here? I mean, in the same context, is it okay to indicate his ability to draw a picture of his mom just as "He said he could draw..." does?


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## Steven David

Angelya said:


> Then does "He said he could have drawn a picture of his mom" work here? I mean, in the same context, is it okay to indicate his ability to draw a picture of his mom just as "He said he could draw..." does?



No, they don't mean the same thing.

He could have drawn a picture of his mom. <<

This means it was possible for him to draw a picture of his mom, but he didn't do it.

It can also mean that it was possible for him to draw a picture of his mom, but we don't know whether or not he did it.

Context tells us which meaning applies.

A previous post has an example of "X could have done Y" in which we don't know whether X did Y or did not do Y.

Of course, we understand that if it was possible for him to draw picture of his mom, then he also had the ability to draw a picture of his mom.

However, with "he could have drawn a picture of his mom", we are not really speaking of ability. We are speaking of what was possible in the past, not his ability in the past and not what he said about his ability.


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## Angelya

Steven David said:


> No, they don't mean the same thing.
> 
> He could have drawn a picture of his mom. <<
> 
> This means it was possible for him to draw a picture of his mom, but he didn't do it.
> 
> It can also mean that it was possible for him to draw a picture of his mom, but we don't know whether or not he did it.
> 
> Context tells us which meaning applies.
> 
> A previous post has an example of "X could have done Y" in which we don't know whether or not X did Y or did not do Y.
> 
> Of course, we understand that if it was possible for him to draw picture of his mom, then he also had the ability to draw a picture of his mom.
> 
> However, with "he could have drawn a picture of his mom", we are not really speaking of ability. We are speaking of what was possible in the past, not his ability in the past and not what he said about his ability.


I got it! Their emphases seem to be dissimilar, right?


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## Steven David

Angelya said:


> I got it! Their emphases seem to be dissimilar, right?



If I understand correctly, yes, you can say this.

However, could you please clarify your question?


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## Angelya

Steven David said:


> If I understand correctly, yes, you can say this.
> 
> However, could you please clarify your question?


I mean, whether saying "could do" or "could have done" in this case, we are not sure whether the person actually did it. Their essential difference is that the former is for showing ability while the other possibility. In the beginning, I mistook your explanation of "could have done" as "could do" because of this similarity because you seem to have misunderstood my question for I was not getting myself across. There was a mistake, and then the other... But now I understand where the trouble is and have a better understanding of them. Really grateful that you have been offering me help on this question so tirelessly!


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## Steven David

Angelya said:


> I mean, whether saying "could do" or "could have done" in this case, we are not sure whether the person actually did it. Their essential difference is that the former is for showing ability while the other possibility. In the beginning, I mistook your explanation of "could have done" as "could do" because of this similarity because you seem to have misunderstood my question for I was not getting myself across. There was a mistake, and then the other... But now I understand where the trouble is and have a better understanding of them. Really grateful that you have been offering me help on this question so tirelessly!




Yes, the former shows ability (in the past - reported speech - indirect speech) while the other shows possibility. However, we have to remember that this is possibility in the past or what was possible.

So the idea is that possibility in the past is not the same as ability in the past, of course. And, at the same time, if it was possible for someone to do something in the past, then, we easily understand that someone also had the ability in the past to do this, as well. Or, at least, we have reason to believe that someone might have had the ability to do something in the past when we say "X could have done Y", which only means it was possible for X to do Y in the past.

And, to keep things clear, we have to remember that "could" by itself means possibility in the present and possibility in the future.

I think I understand or have an idea of why this can be very difficult for people who speak Chinese or a Chinese language.

As I have heard, and have read, many Asian languages do not have verb inflections to distinguish present from past. And determining whether something is present or past depends on context. We depend on context in English, as well. However, of course, as we can see, the verb form provides information about whether or not something is past or present. And the information that verbs provide about whether something is past or present is important and necessary in determining exactly what something means.

You're welcome. I'm glad my replies, comments, and explanations help you.


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## Ivan_I

Steven David said:


> You're welcome. I'm glad my replies, comments, and explanations help you.



So we get this in the *past*.

He was able to lift that stone *yesterday*. (He really lifted it.)
He could lift that stone *yesterday*. (He had the ability to do it. But whether he lifted it or not is not known)
He could have lifted that stone *yesterday*. (He didn't lift it but there was a chance for him to lift it)

He was able to lift that stone *when he was young*. (more or less the same as) He could lift that stone *when he was young*.


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## Steven David

Ivan_I said:


> So we get this in the *past*.
> 
> He was able to lift that stone *yesterday*. (He really lifted it.)
> He could lift that stone *yesterday*. (He had the ability to do it. But whether he lifted it or not is not known)
> He could have lifted that stone *yesterday*. (He didn't lift it but there was a chance for him to lift it)
> 
> He was able to lift that stone *when he was young*. (more or less the same as) He could lift that stone *when he was young*.






> He was able to lift that stone *yesterday*. (He really lifted it.)



We do not know whether or not he lifted it. We only know that he was able too lift it, which is to say he had the ability to lift it.

It's likely that no one would make this statement unless they knew that it was true. And, in this case, it's likely that they saw him lift the stone or had knowledge of the fact that he did lift the stone.

However, this statement only says he was able to. As an isolated sentence, this has nothing to do with whether or not he did, in fact, lift the stone. Context has to tell us that he lifted the stone.



> He could lift that stone *yesterday*. (He had the ability to do it. But whether he lifted it or not is not known)



Yes, this is correct.



> He could have lifted that stone *yesterday*. (He didn't lift it but there was a chance for him to lift it)



This has two meanings, and the meaning that applies depends on context.

1) He did *not *lift that stone, but we know it was possible for him to lift that stone.

2) We have no idea whether or not he lifted that stone. We just know that it was possible that lifted it. Maybe, someone else lifted it. We don't know.



> He was able to lift that stone *when he was young*. (more or less the same as) He could lift that stone *when he was young*.



Yes, this is so for the most part. However, "be able to" is often used in a context in which we know that there's some sort of added challenge, added difficulty, or something to overcome in order to do whatever it is we speak of.


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## Ivan_I

Steven David said:


> We do not know whether or not he lifted it. We only know that he was able too lift it, which is to say he had the ability to lift it.
> 
> It's likely that no one would make this statement unless they knew that it was true. And, in this case, it's likely that they saw him lift the stone or had knowledge of the fact that he did lift the stone.


I see this in a dictionary 

If you say that someone *was able to* do something, you usually mean that they had the ability to do it and they did it. *Could* does not have this meaning.


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## Steven David

Ivan_I said:


> I see this in a dictionary
> 
> If you say that someone *was able to* do something, you usually mean that they had the ability to do it and they did it. *Could* does not have this meaning.




The operative word here is "usually". That's what someone *usually *means, and, in so many words in my previous post, that's what I said. They usually mean that because they saw someone do something or have knowledge that someone did something for a fact. Therefore, someone saw that someone was able to do something. Still, "was able to", without this added information, only means that someone was able to do something. It does not mean that someone, in fact, did something such as lift a stone. 

The fact is that "was able to" only means that. It does not mean that someone actually completed a task such as lifting a stone. 

As for the comparison with "could", yes, both signify ability in context. However, "was (be) able to" often occurs in contexts, though it does not have to, in which there was, or is, some sort of obstacle to get around, some sort of challenge, or something to overcome.


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## s9lavoll

Hi, 
I'd really appreciate if someone could help me. If I want to say that somebody was allowed to do something in the past, e.g. a child was allowed whatever he or she wanted to do, can I also say "He could do" and/or "He was able to"? The one with could sounds okay, but I'm not sure about the second one. 
Thank you so much!


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## owlman5

Hi. Both of them are possible, but I prefer _could _if you want to say that people allowed him to do whatever he wanted to do: _He could do whatever he wanted to do. Nobody ever told him 'No'._


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## s9lavoll

owlman5 said:


> Hi. Both of them are possible, but I prefer _could _if you want to say that people allowed him to do whatever he wanted to do: _He could do whatever he wanted to do. Nobody ever told him 'No'._


Thank you so much! I really appreciate it.


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