“…mustn't have done..”: meanings

runglish333

runglish333

Member
Russian
  1. Can "You mustn't have done that" have a similar meaning to "You shouldn't have done that" / "You were not supposed to do it (but you did)"? (not logical probability but obligation)
  2. Since we have the imperatives like "Have done with that!", wouldn't it be possible to use must to express prohibition of a future action: "You mustn't have done that (by the time the bus reaches here tomorrow)"?
 
    • No, I'm fairly sure 'must(n't) have' always has the probability meaning. You have to switch to a different verb to get the obligation meaning in a perfect tense: you shouldn't have done that; you have to have done that by tomorrow.
     
    I told Susie to make sure the heat was turned off when she went out.
    But now it feels so cold that I think she mustn't have done it.
    ----------
    The dishes are still piled up in the sink. You must not have left them there.
     
    Hi Runglish,

    Entangled has just told you, correctly in my view, that it has the probability meaning, and next post you put it in a context where it can only suggest obligation.

    No wonder it doesn't make sense to Sound Shift.
     
    Thomas Tompion said:
    and next post you put it in a context where it can only suggest obligation.
    Click to expand...

    If you did understand that I was "obviously writing about obligation", and if it does indeed suggest (to the reader) obligation in certain contexts, doesn't it mean that the above does make sense though it may sound odd, awkward and only marginally acceptable?
     
    runglish333 said:
    If you did understand that I was "obviously writing about obligation", and if it does indeed suggest (to the reader) obligation in certain contexts, doesn't it mean that the above does make sense?
    Click to expand...

    No, it simply means that someone was able to understand what you meant to say, despite the fact that you said it in an incorrect way.

    When under stress or busy with something else, my mother would occasionally call me by the name of one of my sisters. The fact that I still knew she was talking to me doesn't mean it wasn't a mistake.
     
    doesn't it mean that the above does make sense
    Click to expand...
    No, it doesn't mean that it makes sense. All it means is that we recognize that you are using it wrongly.

    It does not suggest obligation to the reader. It only suggests to us, in the context of this thread, that you are trying to write about obligation.

    In normal use, "must have done" and "must not have done" are never used to indicate obligation, but only supposition.
    This may seem strange to you, because "must do" and "must not do" always indicate obligation, but that's just the way it is. Sorry.

    (cross-posted)
     
    In my kind of BrE, "you mustn't have done that" doesn't exist to express supposition. In your Susie example, runglish, for me it would be:

    I told Susie to make sure the heat was turned off when she went out.
    But now it feels so     cold warm that I think she can't have done it.

    The form "she mustn't have done it", for supposition, is one that I normally associate with AmE — though our esteemed BrE friends here haven't mentioned that, so I wonder if it's made it's way across the pond.

    Ws    :)
     
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    An interesting point, WS. I must admit that "mustn't have" strikes me as unremarkable for negative supposition. Saying "can't have" seems much stronger to me, as if there is a definite impossibility rather than a mere likelihood of not having done it. I think of "she mustn't have done it" as having evolved from a positive supposition of a negative fact, such as "she must have forgotten to do it", perhaps via "she must have not done it".

    I'm afraid the Susie example is completely illogical. It would only work if either "turned off" is changed to "turned on" or "feels so cold" is changed to "feels so warm", or "heat" to "air conditioning".
     
    I'm with Edinburgher on this and struggled with the Susie example too. Mustn't have can work as an epistemic modal (supposition) but not as a deonic modal (obligation).
     
    natkretep said:
    I'm with Edinburgher on this and struggled with the Susie example too. Mustn't have can work as an epistemic modal (supposition) but not as a deonic modal (obligation).
    Click to expand...
    I certainly thought this initially, Natkretep, but it occurs to me that there are occasions in which the formula can have deontic (obligation) use.

    I'm clear that the answer to the question in the OP, Can "You mustn't have done that" have a similar meaning to "You shouldn't have done that" / "You were not supposed to do it (but you did)"? (not logical probability but obligation), is No. We all seem to be agreed on that.

    However, where we are talking in the present about things which are required (obliged) to have happened in the past, we can use it in a deontic sense, it seems to me.

    The BNC, the British Corpus, bears me out. Here are some examples to illustrate the point I'm making:

    The client must not have previously been refused representation - The modern English legal system. Gunn, N J and Bailey, S H. London: Sweet & Maxwell Ltd, 1993.

    Entrants must be aged 16 to 25, and must not have done any professional modelling or have an existing portfolio - The Sunday People

    In June 1989 the government refused to grant the fundamentalist Islamic Nahdah movement (Mouvement de la renaissance) legal recognition as a political party, on the grounds that by law founders and leaders of parties must not have been convicted of offences warranting more than three months' imprisonment or six months' suspended sentence; 15 Nahdah leaders, although at liberty, still had current convictions dating from September 1987 (see p. 36633).     Keesings Contemporary Archives. Harlow: Longman Group UK Ltd, 1990,

    (1) The Consultant you have chosen must not have been involved in our client's treatment. - Know-how for personal injury lawyers. Walker, Ian. Harlow: Longman Group UK Ltd, 1993.

    Just in case this was exclusively a BE usage, I checked the COCA, the AE Corpus, and found several examples, for instance:

    Previously, that power rested with the California Legislature. Members of the commission must not have run for state or federal office for the previous 10 years, been lobbyists or donated more than $2,000 to any one political candidate. Dueling propositions on legislative borders; Campaign 2010 San Francisco Chronicle

    They can't get married in the Church of England, the Anglican Church, the official church of the country Prince Charles will one day reign over as king, because as defender of the faith, he must not have divorced.     My Word, Fox_Gibson, 2005.

    I'm not at all saying that the must not have + past participle formula is exclusively deontic (obligation) - epistemic (supposition) examples are much more common. The example in the OP must be supposition, in my view, but there are certain cases, such as I've tried to illustrate, where a deontic meaning is idiomatic.
     
    Thanks, TT. Yes, I concede! :) The examples seem to be of a legal or legalistic nature though.
     
    I'm not sure that I agree that those sentences are really deontic in nature, at least not in the direct sense that You mustn't leave your socks in the refrigerator is.

    Consider the sentence You must have received an honorable discharge to be eligible for the Post 9/11 GI Bill (found here). This is logically equivalent to the sentence If you are eligible for for the Post 9/11 GI Bill, you must have received an honorable discharge -- an epistemic use. I see no such straightforward translation for, e.g., You mustn't go out after dark.

    While the phrase "to be eligible" is absent from your examples, I assert that it's implicit in every case. (Except possibly the last, which I think is arguably epistemic already, despite the clear deontic implication: that is, I read it as equivalent to Wordsmythe's "as defender of the faith, he can't have divorced" or perhaps "if he is to be defender of the faith, he must not have divorced".) There's certainly an obligation implied in all cases, but that obligation comes with a specific, and specified, consequence.

    If you still want to call that "deontic", well, I suppose it's not an unreasonable definition. As you note, though, in all these examples the "deontic" component is still present-tense, even though the obligated action is perfect: it is required that X has not happened, which is distinct from runglish's attempted past-tense deontic use.
     
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    a passerby said:
    Consider the sentence You must have received an honorable discharge to be eligible for the Post 9/11 GI Bill. This is logically equivalent to the sentence If you are eligible for for the Post 9/11 GI Bill, you must have received an honorable discharge -- an epistemic use.
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    That is not the correct logical equivalence, in my view. The statement is not making a supposition but stating a condition of eligibility. The true logical equivalence is Only if you have received an honorable discharge are you eligible..., or equivalently If you have not received an honorable discharge, then you are not eligible.
     
    Thanks, Edinburgher, for spotting the glitch in the Susie example. I didn't read it closely enough before copy/pasting!:eek:

    That's also an interesting thought about the possible evolution from "she must have not done it" (which does sound like a supposition to me) to "she must not have done it" (which I hear as a condition or requirement of the kind that TT raised in #12).

    I'm still curious about "mustn't have" for negative supposition. You and I both might say "    She must be kidding!". I might equally say "She can't be serious!" ...

    Now if I were unsure about it being a definite impossibility, but still wanted to express negative supposition, I might say     "She can't be serious, can she?"
    Would you say     "She mustn't be serious, must she?"

    Ws:)
     
    Would you say "She mustn't be serious, must she?"
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    No, I wouldn't; it doesn't feel right somehow. One part of what bothers me here are the tag questions in both versions (mustn't and can't), which take the remarks out of the sphere of supposition altogether, by watering down the supposition with an extra helping of uncertainty. Another part is that, I guess, "mustn't" as a negative supposition seems to suit the past better, while in the present it sounds more like a prohibition (which is in effect how it functions in the legal examples).

    Unfortunately, "can't be serious" can't be used as a serious example because it has acquired a permanent taint of sarcasm as the result of a certain well-known tennis player's famous outburst.
     
    Wordsmyth said:
    That's also an interesting thought about the possible evolution from "she must have not done it" (which does sound like a supposition to me)
    Click to expand...
    "She must have not done it" = "I believe she has not done it" ?
    How would "She must haven't done it" sound? :)
     
    No, it doesn't work. The rule in an English verb phrase is that the negative particle gets attached to the first verb:

    shouldn't have been doing
    can't be said
     
    runglish333 said:
    "She must have not done it" = "I believe she has not done it" ? [...]
    Click to expand...
    Yes, that would be the sense in the case Edinburgher and I were discussing (a positive supposition of a negative fact), but it's not a commonly used construction.
    runglish333 said:
    [...] How would "She must haven't done it" sound? :)
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    As TT and Nat have said, it's wrong. It just isn't English.
    Thomas Tompion said:
    Yes, Nat, but I think we need to explain how if one can write she must have not done it, we shouldn't write she must haven't done it.
    Click to expand...
    - She {has not}{done it} >>> She hasn't done it. ("She has not" is a negative statement.)
    - She {must have}{not done it} >>> She must've not done it. (The "must have" is a positive supposition; "not done it" is the separate negative fact that is being supposed.)

    Something like that? I struggled with that, but a bracket speaks a thousand words.;)

    Ws:)
     
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    Wordsmyth said:
    Yes, that would be the sense in the case Edinburgher and I were discussing (a positive supposition of a negative fact), but it's not a commonly used construction.
    As TT and Nat have said, it's wrong. It just isn't English.
    - She {has not}{done it} >>> She hasn't done it. ("She has not" is a negative statement.)
    - She {must have}{not done it} >>> She must've not done it. (The "must have" is a positive supposition; "not done it" is the separate negative fact that is being supposed.)

    Something like that? I struggled with that, but a bracket speaks a thousand words.;)

    Ws:)
    Click to expand...


    Although this thread is outdated, I feel the need to comment nonetheless.
    WS, although the brackets seem intelligible, there is a major flaw. For example, why is "must have" a positive supposition? You could move the bracket to the left and argue that "must have not" is a negative one. Or you could say that "she has (not done it)" is a positive supposition because it implies that "she has successfully completed the act of not doing something". However, the answer has nothing to do with the placement of "not". Using MUST HAVE NOT/ MUST NOT HAVE to express a supposition in the first place is incorrect. You should use "must have failed to do smth" instead. It is considered to be the correct version.
    Hope this helps.
     
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