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Must vs. must have to

Discussion in 'Italian-English' started by andrea.rusignuolo, May 5, 2009.

  1. andrea.rusignuolo Junior Member

    Hello everyone,
    I was reading a grammar book and I came across this phrase:

    "I can't start the computer. You must have to know a password".

    Is it also correct to say/write:

    "I can't start the computer. You must know a password" dropping "have to"

    Thanks in advance
  2. brian

    brian Senior Member

    AmE (New Orleans)
    must have to (where must implies necessity) is completely wrong. Always.

    It's because must = have to, so must have to is like saying deve dovere. So if you consider must to imply necessity in your sentence, then:

    You must have to know a password. = Devi dovere sapere una password. :cross:

    The only case in which must have to is okay is when must implies probability, like in He must think that you like him. = Penserà che lui ti piaccia. So, an example of must have to in this context:

    A: The ticket window is closed! Where are we supposed to buy tickets?
    B: We must have to buy them at the door. = Mi sa che dobbiamo comprarle alla porta.

    Now, back to your example, think of must as implying probability, not necessity:

    You must have to know a password. = Mi sa che bisogna sapere una password. :tick:
    Last edited: May 5, 2009
  3. Jamis Senior Member

    You must have a password.
    You have to have a password.

  4. andrea.rusignuolo Junior Member

    I can't start the computer. You must have to know a password.
    Non riesco ad accendere il computer. Mi sa che devi sapere una password.

    Cito le due righe di spiegazione del libro:
    "We can use must have to to say that we conclude something based on what we know about a present situation and must have had to to conclude something about a past situation"

    Poi da i due esempi dei due casi. Uno è quello sopra.
    "Jhon wasn't at home when I went round. He must have had to go out unexpectedly".

    Are these expression common? Otherwise I will try to forget them cause they're really confusing me.

    (Ragazzi siete troppo veloci nel rispondere non riesco a starvi dietro :D)
    Last edited: Nov 26, 2013
  5. brian

    brian Senior Member

    AmE (New Orleans)
    Jamis, must can mean two different things in English: 1) necessity (You must leave.), and 2) probability (He must have left.)

    The example sentence is: You must have to have a password. This expresses probability, (2) above. The idea is: Hmm.. it looks like you have to have a password. It is a matter of deduction on the part of the speaker.

    Your sentences--You must have/have to have a password--express necessity, (1) above. So they are different.


    They are very common.
    Last edited: Nov 26, 2013
  6. andrea.rusignuolo Junior Member


    Thanks a lot Brian

    Ok, now I've clear the difference meaning in the present, but i still have problems with past tense.

    What's the difference between:

    When I got back home I found that the house had been damaged. They must have climbed/must have had to climb over the fence in the back garden.

    Don't both express probability in the past based on something that you're seeing?
  7. brian

    brian Senior Member

    AmE (New Orleans)
    Yes, the must in both expresses probability in the past, BUT...

    must have climbed expresses the probability that they climbed: Mi sa che (sembra che) hanno scavalcato il recinto / Avranno scavalcato il recinto.

    must have had to climb expresses the probability that they had to climb (necessity): Mi sa che hanno dovuto scavalcare il recinto / Avranno dovuto scavalcare il recinto. It is a combination of must (probability) + have to, in the past (necessity).
  8. andrea.rusignuolo Junior Member

    Now it's clear.
    Thanks again
  9. Veledan Senior Member

    Stoke, UK
    English - BE
    Wouldn't that be the other way round, i.e. Penserà che lui ti piaccia?

    I'm afraid they're extremely common, Andrea. You don't hear must used much to mean 'dovere' -- it's usually said 'have to'. If you hear 'must' in speech, it'll often mean 'probably'.

    Yes, they do and they're both right, but the first one keeps the sense of 'dovere' in there:

    They must have climbed... -- Mi sa che hanno scalato...
    They must have had to climb... -- Mi sa che hanno dovuto scalare...

  10. brian

    brian Senior Member

    AmE (New Orleans)
    Oops, definitely. I was concentrating on the must part too much and forgot what else I had written.
  11. andrea.rusignuolo Junior Member

    Yes Vel. You're right.
    I was so into my question that I didn't notice it.

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