have to go/must go

[Vladv1]

In film Mortal Combat there is a scene where a group of women see a dragon in the distance coming their way. Terrified, one of them says "We must go". I am confused because I was taught that when we do something under external circumstances, we should say "have to"

 

[5jj]

I was taught that when we do something under external circumstances, we should say "have to"

That's a reasonable guide to how many people use have to, but it's only a guide. There is little logic in how some native speakers use must and have to.

 

[emsr2d2]

In the film Mortal Combat, there is a scene where a group of women see a dragon in the distance coming their way. Terrified, one of them says "We must go". I am confused because I was taught that when we are obliged/forced to do something under due to external circumstances, we should say "have to".

Note my corrections above. Some people will try to tell you that there are circumstances under which one works and the other doesn't, but I can't say I've ever seen a compelling explanation.

 

[5jj]

Here is something I wrote a few years ago:


A further complication with these two verbs is that many Americans appear not to use 'must', so the difference felt by some native speakers is unreal for others.

For many speakers of BrE, 'must' suggests an obligation imposed by the speaker, 'have to' an obligation imposed by somebody else:

Teacher: You must do this homework tonight. (I, the teacher, impose the obligation.)

Mother: You have to do this homework tonight. (The teacher has imposed this obligation, not I, the mother.)

Even this difference is not always observed when the subject is 'I'. In an utterance such as "Sorry, I have to go now", the speaker may use 'have to' when there is no external obligation, to suggest a polite unwillingness to leave.


Some people appear to feel that 'must' is somehow stronger than 'have to'; however I have heard others claim that 'have to is stronger than 'must', so that's no help.

 

[SoothingDave]

Yes, my instinct is to say that there is no difference in meaning. If anything, we would consider "must" to be more formal.

 

[jutfrank]

There absolutely is a semantic difference and there's quite a bit of semantics literature on it. The disagreement lies in what exactly the difference is.

My own shot at describing the difference in the broadest way I can is to say that 'must' carries more authority. That's it. This explains why it's much more common in formal written language, and also why people in the past (I think it was Geoffrey Leech in the early 1970s) saw a difference in the source of obligation—is it not after all more likely that an external body would seek to present as an authority? Still, the idea that it's all about the source is just wrong, and makes for a completely useless if not damaging rule to teach learners.