'Would have' vs. 'must have'

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nowt000

Senior Member
Mandarin
1. The fist-pumping, standing ovation, raucous cheering and wild applause certainly led you to believe they must have won it all.

2. This 2006 photo must have been taken when Tommy Lee Jones was overcome with joy.

3. They were very good and it must have taken lots of practice to do all those things.

-- All taken from Improve Your Writing skills

Can I use 'would have' rather than 'must have' in the three examples without much change in meaning?
 
  • The Newt

    Senior Member
    English - US
    I don't think we would ever use "would have" in the first example. It could be used in the other two, but it makes the assertion a bit less adamant.
     

    nowt000

    Senior Member
    Mandarin
    I don't think we would ever use "would have" in the first example. It could be used in the other two, but it makes the assertion a bit less adamant.
    Could you tell me why? Is it because the first example contains 'certainly' which would contradict the tentative nature of 'would'?
     

    nowt000

    Senior Member
    Mandarin
    I'm not sure why, but I don't think "certainly" is the problem. It may have to do with "believe."
    The following five examples are taken from the same link. Do they sound iffy to you?

    I believe every person on earth would have committed at least one of those acts.

    Wollbrinck said he found it difficult to believe Mabry would have been targeted by the shooter.

    Most believe Langer would have played before Sunday.

    I believe the executives who run the Olympics would have caved within four hours.

    All the tickets collected fit the time frame that authorities believe Porco would have driven the interstate both to and from Rochester.
     

    The Newt

    Senior Member
    English - US
    The following five examples are taken from the same link. Do they sound iffy to you?

    I believe every person on earth would have committed at least one of those acts.
    [...].
    Most or all of them seem to have a certain degree of ambiguity. Just looking at the first one, does it mean "It must be true that every person had committed one of those acts" or is it simply a conditional? It's hard to say.
     

    Englishmypassion

    Senior Member
    India - Hindi
    Could you tell me why?
    Would (have) is used to express speculation or mere guess, not conviction based on clear evidence. "Must (have)", on the other hand, is used to express conviction or assurance based on evidence. In your context you have clear visual evidence to believe that they have won.
     

    se16teddy

    Senior Member
    English - England
    Would (have) is used to express speculation or mere guess, not conviction based on clear evidence. "Must (have)", on the other hand, is used to express conviction or assurance based on evidence. In your context you have clear visual evidence to believe that they have won.
    :thumbsup: Must have" means that there are specific and convincing grounds for belief - either a convincing chain of logic or convincing evidence. Would have is more speculative.
     

    nowt000

    Senior Member
    Mandarin
    Most or all of them seem to have a certain degree of ambiguity. Just looking at the first one, does it mean "It must be true that every person had committed one of those acts" or is it simply a conditional? It's hard to say.
    Thank you! <by the way>, can I use 'should have' instead in these examples without considerable change in meaning??


    < Edited to write out abbreviation in full. Cagey, moderator >
     
    Last edited by a moderator:

    The Newt

    Senior Member
    English - US
    Please walk me through them. Much obliged!!
    Let's start with the first: "I believe every person on earth would have committed at least one of those acts." "Should have" in modern English would suggest that the speaker thinks that every person on earth has a moral obligation to have committed one of those acts.
     
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