The following example is taken from source

A：We saw a police helicopter overhead yesterday morning.

B：Really? They would have been looking for those bank robbers.

The website says that it is an example of usage of would to express an assumption, presumption or expectation in the past.

As this post indicates, the example here does not mean a hypothetical scenario or a past future tense, but a speculation about a past event.

I'm wondering whether the post was correct in explaining such usage. Please share some wisdom!

Only a few grammar books say "would have + past participle" can be used in this way. The following are a couple of the sources I could find, but I don't know whether they are reliable to believe.

Would + perfect. This use of would signals what we expect somebody to do:

John would have scheduled the meeting.

In this case, it tells us that the speaker expected John to schedule the meeting. We do not know if John actually scheduled the meeting.

-- McGraw-Hill's Essential ESL Grammar, for Intermediate & Advanced ESL Students (2008)

and

One of the children offered to help. That would have been Julie. (assumption about the past.)

-- Mastermind Use of English

Kinzle B

Posted 2014-04-12T16:39:55.080

Reputation: 7 089

I think "They will have been looking for those bank robbers." is not correct. Future perfect (will have been) requires a reference time in the future, which is missing in this example. – Nico – 2014-04-12T17:28:29.190

I think this link may help you.

– Nico – 2014-04-12T17:32:27.650

Zhanlong, do you have recurring issue with this concept? If so, I suggest that you post a question specifically to address the generic learning issue - such as learning model verbs or will and would specifically. Just having a hard time "getting it". We've all been there at some point where something just doesn't want to fit into our brain. As a quick suggestion, sometimes it's related to a brain neural net that needs to grow so it's biological, and that means drills every day, take few days break, repeat. Success comes in weeks or months, but will come. – CoolHandLouis – 2014-04-12T19:29:46.357

@Nico Here will is a modal-verb representing a confident inference! It's not a future auxiliary here. "Will have + past participle refers to the past."(PEU 629.3) – Kinzle B – 2014-04-12T22:28:33.897

Would you plz help me clear my doubts about this question? I have revised my question a lot. @StoneyB – Kinzle B – 2014-04-14T11:00:23.163

This question appears to be off-topic because the OP has similar doubts though they are answered before. – Maulik V – 2014-04-14T12:58:28.670

@MaulikV please, could you add a link? – Nico – 2014-04-14T12:59:55.097

@Nico check the questions the OP has asked. And I said similar doubts. – Maulik V – 2014-04-14T13:01:35.073

@ZhanlongZheng I would suggest the following exercise: see the examples of use of "would have been" in the books linked here and try to classify them into hypotherical scenario, speculation about a past event, or something else. and post another question when you find an example you can't classify.

– Nico – 2014-04-14T13:03:13.550

1That's not fair. Each of my question concerning "would" refers to different usage of this word, just like seeing a diamond from different aspects! – Kinzle B – 2014-04-14T13:03:22.997

@ZhanlongZheng alternatively, I'm sure you can find someone at the ELL chat room to discuss concrete examples. – Nico – 2014-04-14T13:07:55.240

1@MaulikV sorry. I thought your comment was meant to flag this question as duplicate. – Nico – 2014-04-14T13:09:34.553

I can figure out most of these usages now, and I don't need those exercise. I got high marks even in some high level tests on English. I passed Financial Risk Manager exam. I just wanted to go deep into language. That's it! – Kinzle B – 2014-04-14T13:09:57.030

@ZhanlongZheng sorry. I didn't mean to offend you. Could you clarify your question? Are you only asking whether "would have been" can be used to express speculation? Or for a reference that explains that? – Nico – 2014-04-14T13:13:05.310

As Nico said, I think you seek discussion rather than answers. True, a chat is better in that sense. Also, if you need deep analysis of modal verbs, I guess, all the topics will attract close-votes marked with too broad a topic to discuss. Certainly, all the usages of the verb is cannot be answered. – Maulik V – 2014-04-14T13:13:22.310

Yes, those books are not as authoritative as PEU. I have no idea whether they are right or just misleading. Other important sources like PEU do not say would can be used in that way, so I wanted to know more about it. @Nico – Kinzle B – 2014-04-14T13:18:59.900

I might be able to give you a reference when I get home. – Nico – 2014-04-14T13:24:07.200

1No, not that deep. I am not a linguist. I have understood nearly the whole picture. This should be my last puzzle piece. Maybe it's also the hardest one since even PEU avoids to include this usage. I am very eager to get a good answer to it. @Maulik V – Kinzle B – 2014-04-14T13:29:14.727

BTW. No offense. Even you said youself that "They will have been looking for those bank robbers." is not correct the other day, but others think otherwise. Therefore, I hope a good answer will solve this puzzle. @Nico – Kinzle B – 2014-04-14T13:57:06.403

@ZhanlongZheng I think that's a different example. There you meant to express certainty, but instead the sentence was written as "Really? They will have been looking for those bank robbers." I removed my answer, because your question doesn't include that example any longer. If you think it's still useful I will undelete my answer. – Nico – 2014-04-14T14:06:22.703

Answers

The first thing I would say about modal verbs is that their usage extends over many different contexts and so any general rules are bound to fail when taken out of context.

Outline

Use of 'will' and 'would' to express belief
Other uses
The answer

1. Use of 'will' and 'would' to express belief

(Credit for this section should go to @snailboat)

To illustrate the difference in use of 'will' and 'would' for expressing certainty, snailboat suggested the following sentences at the ELL chat room:

1A. I'm sure they have been looking for those bank robbers.

1B. I'm sure they will have been looking for those bank robbers.

2A. I'm sure they had been looking for those bank robbers.

2B. I'm sure they would have been looking for those bank robbers.

In sentences 1A (they have been) and 2A (they had been) the speaker knows they have/had been looking for those bank robbers. The main difference is that the use of present perfect in 1A (they have been) indicates that the search has lasted at least until now.

In sentences 1B (they will have been) and 2B (they would have been) the speaker expresses a belief:

in sentence 1B (they will have been), the speaker expresses the belief that they have been looking for those bank robbers.
in sentence 2B (they would have been) the speaker expresses the belief that they had been looking for those bank robbers.

2. Other uses

Again, a word of caution, the interpretation above is not unique and can change if the context changes. This section shows other possible uses of will have been and would have been.

To express a hypothesis

I'm sure they would have been looking for those bank robbers if they had any manpower to spare.
To express an event in the future

They will have been looking for those bank robbers for hours before the CCTV footage is shown on tomorrow morning's News.

3. The answer

Let's now consider the example in your question:

A： We saw a police helicopter yesterday morning.

B： I'm sure they would have been looking for those bank robbers.

To be able to use "will have been" is necessary to change the context as described in the first section of this answer:

A： We have seen a police helicopter.

B： I'm sure they will have been looking for those bank robbers.

Nico

Posted 2014-04-12T16:39:55.080

Reputation: 2 540

In your last example, the reply (B) is preposterous—it is not called for by the tense of the query (A). The simplest, most apt, nearly obvious answer is "I'm sure they were looking for the robbers. And the best way to phrase (B) in OP's original to express presumption, rather than speculation, is "They must have been looking for the robbers." – Brian Hitchcock – 2015-04-20T05:13:31.960

@BrianHitchcock I also think that "must've been" sounds more natural. The use of perfect forms varies with the dialect, and for example, I don't think the answer "they were" would be the most apt in BrE. Do you think reply (B) is incorrect? It may not be the most apt reply, but my intention was to give an example of usage of "will have" to express belief. – Nico – 2015-04-21T14:29:17.993

"will have been" is a future perfect. If tomorrow it is announced that they were looking for a robber, then you will have been proven corect in your belief. but they either were or were not looking for the robber, regardless of your belief or conjecture. – Brian Hitchcock – 2015-04-22T07:04:51.207

@KinzleB In the OP's context, only "would have been looking for.." applies, because the use of "we saw..." (simple past) implies that the search is also in the past and doesn't extend to the present (at least in BrE). Whereas "will have been looking for.." suggests the search extends to the present or is relevant at present. – Nico – 2015-10-01T14:48:40.547

Thank your for your feedback. Can I say here would is used as the past form of will rather than an irealis marker? Is it to say "would have looked for.." in this context? @Nico – Kinzle B – 2015-10-01T15:28:40.250

@KinzleB I would say that expressing belief is one of the many forms the irrealis mood can take. The OP's example, "would have been looking for..", is expressing belief, and is also referring to an event that would have taken place in the past. I wouldn't treat the past tense and the irrealis mood as excluding terms.

– Nico – 2015-10-02T16:00:01.560

Here comes my confusion and the reason why I asked this question: When we say an event would have taken place in the past, it often means that it didn't take place. It's counterfactual. While in this context the speaker is pretty sure it did happen. It doesn't look like a normal use of "would have done". Plz help clarify it. @Nico – Kinzle B – 2015-10-02T16:19:04.813

1@KinzleB No, in the OP's example, B isn't pretty sure, B isn't expressing certainty. Note that B starts the sentence with "Really?". B is expressing a belief. B believes that the police had been looking for those bank robbers. – Nico – 2015-10-02T23:34:21.927

@Nico Ah, I see. I thought it didn't fit into the conditional category. I was wrong. I realize I didn't clearly state my question. That was a fault on my side. So what is the implicit protasis for "would have been looking for" here? – Kinzle B – 2015-10-03T00:52:54.180

@KinzleB Assuming, you're following the classification in Wikipedia, I would say it's an example of potential mood, because it's expressing probability.

– Nico – 2015-10-03T09:00:55.077

@KinzleB The subject of modal verbs is very complicated. The same "would have done" conveys different meanings depending on the context. Searching Google books to find real uses of "would have done" yields many different types of usage. A comprehensive classification of all of them is necessary complicated.

– Nico – 2015-10-03T14:36:12.047

In this conext, what would be the implicit protasis for it? And would could/might have looking for convey the same meaning here? Please, this is alI I want to know here. @Nico – Kinzle B – 2015-10-03T14:59:52.370

@KinzleB It isn't a conditional sentence. – Nico – 2015-10-03T15:02:59.823

That makes sense now. What about my second question? Would my alternatives convey the same meaning here? @Nico – Kinzle B – 2015-10-03T15:15:42.550

@KinzleB without giving it much thought (I'm not going to try to analyse all those possibilities), I would say not only the don't convey the same meaning, but also, some of them may not even be appriopriate in the original context. – Nico – 2015-10-03T15:47:18.753

I opened a new question on "will have + past participle" http://ell.stackexchange.com/questions/70317/ Could you answe it? @Nico

– Kinzle B – 2015-10-17T10:01:21.690

Excellent answer. As an aside, if I asked you, "What do you think? Do you want to walk to the concert?" then a perfectly reasonable response would be: "I think we would be late. Let's take a train." Incidentally, this doesn't mean I disagree with what you wrote here – in fact, it's quite the opposite! As you said initially, "their usage extends over many different contexts .. so any general rules are bound to fail" in another context. I would fully agree. – J.R. – 2014-04-14T14:58:01.607

@J.R. I started to edit my answer after a chat with snailboat and I ended up rewriting the whole answer. I hope I didn't removed any of the bits you liked. – Nico – 2014-04-14T17:11:22.293

Is the sentence "I'm sure they will have been looking for those bank robbers" truly grammatical? I've read that a sentence using the Future Perfect Continuous should mention a point in the future when the action will stop. – CowperKettle – 2014-10-19T07:44:20.513

1@CopperKettle, how you read the phrase "they will have been looking for ..." depends entirely on the context. In section 2, I've given an example that can be read as what you call "Future Perfect Continuous"; the purpose of section 1, however, was to give an example that expresses belief (the purpose is not to locate an action in the future). – Nico – 2014-10-22T09:17:08.713

A： We saw a police helicopter overhead yesterday morning.

B： Really? They would have been looking for those bank robbers.

This sounds incorrect to me. Personally, I would say something like "Really? They WERE PROBABLY looking for those bank robbers." In order to use this verb tense here, you would need a situation like...

A: Our police helicopter was supposed to be out looking for those bank robbers yesterday.

B: Really? The helicopter would have been responsible for locating and apprehending them, but I hear the helicopter ran out of fuel right before the call and had to return to base.

RedDragonWebDesign

Posted 2014-04-12T16:39:55.080

Reputation: 1 251

I'm writing this as an answer because it is too long to be a comment, so it's not really an answer to the question; for the answer see Nico's. I'm adding some information that I think will make things a little clearer for the OP.

A: We saw a helicopter yesterday morning .

B: I'm sure they would have been looking for those bank robbers.

Here, would is used as the past of will. So let's look at this as the past of will + infinitive without to. The verb phrase is used to express certainty, which, in a sense, is a certain speculation or an assumption.

The infinitive without to appears to be a perfect one, in a progressive form, i.e. have been looking. This is from the tense of the event (They have been looking for those bank robbers).

Now let's look at the examples you gave.

John would have scheduled the meeting.

One of the children offered to help. // That would have been Julie.

In would + perfect above, we can probably view would as a less definite form of will that is used to express certainty (I take it that you have Practical English Usage; these are under 633.2 and 629.3 respectively.) This, too, can be considered a speculation or an assumption.

The perfect here is used just to show that the event is in the past--at the point before the time of speaking (see this post for extremely thorough detail).

All of the above is how I view all the examples from my understandings; they shouldn't be regarded as authoritative. If anyone finds any mistake in this post, I'll be glad to correct it as soon as possible.

user1513

Posted 2014-04-12T16:39:55.080

Reputation:

You say I've never seen the more definite form, will + perfect, used this way. Why is that? – Kinzle B – 2014-04-15T16:17:10.440

Probably because will + perfect is mainly used to refer to the future, what you may have learnt as the future perfect tense. It may cause confusion if they use it this way. This is the only reason I can think of. If you may excuse, I would say that I see it as just the way they use their language. – None – 2014-04-15T16:21:55.593

but PEU 629.3 also says "will have +pp" can be used to refer to the past. e.g. We can't go and see them now - they will have gone to bed. However, PEU does not say how often it is used in conversation and in written texts. – Kinzle B – 2014-04-15T16:31:12.647

Oh, then that's a mistake on my side. I'm taking that line out. I think it's just that I don't have enough experience; if it were something rare, then PEU would explicitly state so. – None – 2014-04-15T16:34:44.427

"To express a hypothesis ....

I'm sure they would have been looking for those bank robbers if they had any manpower to spare." ... Is the hypothesis in the present? – Gamal Thomas – 2019-11-13T12:47:06.973

-1

1B is incorrect "I'm sure they will have been looking for those bank robbers"--makes no sense. "I'm sure they will have found those bank robbers by morning. By tomorrow morning, they will have been looking for those robbers for over 20 hours." makes sense. You need a reference of a stopping point in the future.

JKopp

Posted 2014-04-12T16:39:55.080

Reputation: 1

"I'm sure they will have been..." makes perfect sense. It is quite a common usage. – Chenmunka – 2019-11-09T10:49:11.187

"Would have + past participle" construction can be used to express speculation about the past?

Answers

1. Use of 'will' and 'would' to express belief

2. Other uses

3. The answer