can't have and couldn't have

Jigen

Senior Member
Italian
1)I don't thin anything is missing,they(can't/couldn't)have found my jewelry.
2)The thieves(can't/couldn't )have been here .
3)He (can't/couldn't )have prepared for his interview well enough.

My book says that in each case is only possible"can",why is it?I mean can I also use "couldn't" in each sentence to express the same meaning?
 
  • Liinaa

    New Member
    Portuguese
    In my text book is written that we use " Modal verb + have + Past Participle " to do an expeculation about the past", notice that we use this construction for something that happened before now.
    When we speculate about the present with modal verbs we use infinitive without to E.g : It must be...
    I think that according to the rule both are correct because both are modal verbs : Can't/ couldn't.
    May a native speaker can give us a better explanation.

    Textbook: Aspire Upper Intermediate
     

    Glasguensis

    Signal Modulation
    English - Scotland
    There is a difference in meaning, in my opinion.

    1)I don't think anything is missing, they can't have found my jewelry. I deduce that them not finding the jewelry must be the reason nothing is missing.
    1)I don't think anything is missing, they couldn't have found my jewelry. I believe it was impossible for them to find my jewelry.

    2)The thieves can't have been here. I deduce that they weren't here
    2)The thieves couldn't have been here. I believe it was impossible for them to be here

    3)He can't have prepared for his interview well enough. I deduce that he didn't prepare sufficiently
    3)He couldn't have prepared for his interview well enough. I believe it was impossible for him to prepare sufficiently

    However, in the third example I believe the difference is less clear-cut than in the other two - many people would see them as interchangeable.
     

    VicNicSor

    Banned
    Russian
    1)I don't think anything is missing, they can't have found my jewelry. I deduce that them not finding the jewelry must be the reason nothing is missing.
    1)I don't think anything is missing, they couldn't have found my jewelry. I believe it was impossible for them to find my jewelry.
    Hello. Is the impossibilty for them to find my jewelry the reason that nothing is missing, too? (in the latter sentence)
     

    Glasguensis

    Signal Modulation
    English - Scotland
    For me it's more an "and". I don't see anything missing, and no need to check my jewelry because they couldn't have found that.
     

    VicNicSor

    Banned
    Russian
    For me it's more an "and". I don't see anything missing, and no need to check my jewelry because they couldn't have found that.
    To be honest, I can't imagine a context for this sentence:). If they were looking for my jewelry... why did they do that at all if nothing was missing?
     

    VicNicSor

    Banned
    Russian
    IF... nowhere does it say that they were looking for jewellery.
    Ah, I see!

    But then, I see the former sentence a bit differently, Glasguensis:
    I know that nothing is missing and that's why it's impossible that they found my jewelry (they looked for). Even if they have found something -- it's not mine. Does this work?
     
    Last edited:

    Glasguensis

    Signal Modulation
    English - Scotland
    Ah, I see!

    But then, I see the former sentence a bit differently, Glasguensis:
    I know that nothing is missing and that's why it's impossible that they found my jewelry (they looked for). Even if they have found something -- it's not mine. Does this work?
    If this is your interpretation of the "can't" variant, then I don't see a difference from what I said.
     

    VicNicSor

    Banned
    Russian
    If this is your interpretation of the "can't" variant, then I don't see a difference from what I said.
    You said: I deduce that them not finding the jewelry must be the reason nothing is missing. which means they looked for, didn't find anything, and that's why I conclude that I hadn't lost anything... Am I wrong?
     

    Glasguensis

    Signal Modulation
    English - Scotland
    Yes, you're wrong. I see that nothing is missing, and I deduce that they didn't find the jewelry. Whether they looked for the jewelry is unknown, all that is known is that they didn't find it.
     
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