Student or Learner
I have some doubts when it comes to the usage of 'must' and 'have to', because it seems to depend solely on the context in sentenses like:
'We have to go on holidays, we should travel more often' and
'We must go on holidays, we should travel more often'
the first one would mean that we have to do it because maybe we want to be like the others which would imply an external force and keeping up with the Joneses, and the second one that we feel this is our inner need and we want it for ourselves - am I right?
and this one:
'Can we meet tomorrow? "Sorry, no, I have to go to the dentist at 11.00' (I have to go because of the circumstances - a toothache?) vs.
'Can we meet tomorrow? Sorry, no, I must go to the dentist at 11.00' (?)
'You must be joking' vs.
'You've got to be joking' (no ideas here...)
Which form is correct?
(Not a teacher)
I can also add the following two meanings:
1. I have to go and talk to her (when she called me).
2. I must go and talk to her (I need to speak with her).
There is no simple answer to the question, and you will find different books giving different advice. I have read, for example that must implies a stronger obligation than have to; I have also read that have to is stronger!
American colleagues tell me that must is rare in AmE, which suggests that Americans would not be aware of the difference I am about to mention.
I feel that in BrE, have to implies an externally imposed obligation, must an obligation imposed by the speaker.
1. Father to son: You have to do your homework.
2. Father to son: You must do your homework.
In #1, the father is thinking perhaps of the school rule;
In #2, the father is giving the order.
With I, the speaker may sometimes choose to use have to rather than must when there is a self-imposed (ie, speaker-imposed) obligation. This suggests that the speaker is forced by external obligations to do something over which s/he has no control.
Oh, it's 8 o'clock. I have to go. (The speaker is suggesting s/he has no choice. This implied reluctance to go is a social convention of politeness.)