Could have

Question

Hi,I posted about 'could have' previously and dimsumexpress helped clearing one point but I need my other inquiries to be tackled as well in my first post if possible.Now I have another two sentences that I need to find out about.1.'By the time he arrives at the station, the train will have left.'2.'By the time he arrives at the station, the train could have left.'3.'By the time he has arrived at the station, the train will have left.'I know No1 is correct, but what a bout No2 and No3.Using the construction 'could have' for hypothetical future as-dimsumexpress-pointed out for me is new to me and I need further explanation if possible.The sentence I was asking about in my first 'could have' post was:'...the original cost of the dam was estimated at$25billion, but by the time it is completed this could have risen to $75billion or more.'Does 'is completed' show the future here? Can one say 'has been completed' instead?Can one say'could rise' ?What is the difference between 'possibility' and 'hypothetical future'?Sorry!!! for repeating the topic, but I felt I needed more insight into it.

AlpheccaStars · Accepted Answer

Hi,

You are asking about future perfect tenses. These are rather rare. The situation is about completion of an event in the future relative to another event in the future.

1.'By the time he arrives at the station, the train will have left.' OK. The simple present is used to express a future time event.
2.'By the time he arrives at the station, the train may /could have left.' OK. The present is used as future time. The modal expresses future possibility..
3.'By the time he has arrived at the station, the train will have left.' No, it's not logical to me, because "has arrived" refers to a past, not future, time.

Nsfs2 · Answer

Thanks,AlpheccaStars.

Could you help clearing up my other questions,please.I know dimsumexpress is helping, but two are better than one.

CalifJim · Answer

nsfs21.'By the time he arrives at the station, the train will have left.'
2.'By the time he arrives at the station, the train could have left.'
3.'By the time he has arrived at the station, the train will have left.'

The second one seems anomalous to me.

The train could have left ~ It's possible that the train (has) left.

The possibility that the train has already left (in the past) doesn't seem related at all to the time of his arrival.

For this idea, I'd say, The train might leave before he arrives at the station.
________

The other two (1 and 3) seem fine to me.

CJ

Nsfs2 · Answer

CalifJim nsfs21.'By the time he arrives at the station, the train will have left.'2.'By the time he arrives at the station, the train could have left.'3.'By the time he has arrived at the station, the train will have left.'The second one seems anomalous to me.The train could have left ~ It's possible that the train (has) left.The possibility that the train has already left (in the past) doesn't seem related at all to the time of his arrival.For this idea, I'd say, The train might leave before he arrives at the station.________The other two (1 and 3) seem fine to me.CJ

Thanks,CalifJim.

Could you please tell me what you think of the following ?

'...the original cost of the dam was estimated at$25billion, but by the time it is completed this could have risen to $75billion or more.'

Does 'is completed' show the future here? Can one say 'has been completed' instead?
Can one say'could rise' ?
What is the difference between 'possibility' and 'hypothetical future'?
Is '...could have risen...' not similar to what you stated a bout the 'anomalous second sentence' above?

AlpheccaStars · Answer

CalifJim nsfs21.'By the time he arrives at the station, the train will have left.'2.'By the time he arrives at the station, the train could have left.'3.'By the time he has arrived at the station, the train will have left.'The second one seems anomalous to me.The train could have left ~ It's possible that the train (has) left.The possibility that the train has already left (in the past) doesn't seem related at all to the time of his arrival.For this idea, I'd say, The train might leave before he arrives at the station.________The other two (1 and 3) seem fine to me.CJ

It just goes to show that even native speakers can have different views! Probably we normally get in that habit of expressing a concept or sequence of tenses one way, and other possibilities seem a bit strange.

The second one reads better with the adverb already:

By the time he arrives at the station, the train could/may/might have already left. (ie. He was cutting it close!)

Thinking more on the third one, it seems more plausible now. Here is a set of variations, which are OK to me.

By the time he gets halfway to the station, he will realize that he should have taken his umbrella.
By the time he gets halfway to the station, he will have realized that he should have taken his umbrella.
By the time he has reached the point halfway to the station, he will realize that he should have taken his umbrella.
By the time he has reached the point halfway to the station, he will have realized that he should have taken his umbrella.

Nsfs2 · Answer

AlpheccaStars CalifJim nsfs21.'By the time he arrives at the station, the train will have left.'2.'By the time he arrives at the station, the train could have left.'3.'By the time he has arrived at the station, the train will have left.'The second one seems anomalous to me.The train could have left ~ It's possible that the train (has) left.The possibility that the train has already left (in the past) doesn't seem related at all to the time of his arrival.For this idea, I'd say, The train might leave before he arrives at the station.________The other two (1 and 3) seem fine to me.CJIt just goes to show that even native speakers can have different views! Probably we normally get in that habit of expressing a concept or sequence of tenses one way, and other possibilities seem a bit strange.The second one reads better with the adverb already:By the time he arrives at the station, the train could/may/might have already left. (ie. He was cutting it close!)Thinking more on the third one, it seems more plausible now. Here is a set of variations, which are OK to me.By the time he gets halfway to the station, he will realize that he should have taken his umbrella.By the time he gets halfway to the station, he will have realized that he should have taken his umbrella.By the time he has reached the point halfway to the station, he will realize that he should have taken his umbrella.By the time he has reached the point halfway to the station, he will have realized that he should have taken his umbrella.

Clearer now.Thanks.

CalifJim · Answer

nsfs2.the original cost of the dam was estimated at$25billion, but by the time it is completed this could have risen to $75billion or more.'

Judging only by the text you provided, you need one of these:

... but by the time it [is / has been] completed, this [could / may / might] rise to $75 billion or more.

nsfs2Is '...could have risen...' not similar to what you stated a bout the 'anomalous second sentence' above?

Yes. It's the same. "could have".

nsfs2What is the difference between 'possibility' and 'hypothetical future'?

A possibility can apply to the present; a hypothetical (i.e., imagined) future cannot.
You can't have a hypothetical future unless you already have the possibility.

I can imagine that you may reply to this post, for example, (hypothetical future) only because I believe the possibility exists for you to do it if you wish to.

CJ

Nsfs2 · Answer

Lots of thanks to all dear teachers.

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