[Grammar] Must vs have to

[Walt Whitman]

English teacher
Sorry this will be a little long…
Most grammars for ESL students maintain that the difference between “must” and “have to” is very small and usually go on stating that “must” is used for an “inner” obligation coming from the speaker whereas “have to” is used for objective necessity (an external obligation coming from someone else, or some institution); I personally think that the difference isn’t that small, it is actually quite significant.
Would you agree with the possible meanings attributed by grammars to each of the following?

(1)
a. I must get my hair cut.
I feel that my hair is too long.
b. I have to get my hair cut.
I'm going for an interview and everyone tells me that I should look smart.

(2)
a. We must start looking for a new house.
We are tired of our old house and feel we want a change.
b. We have to start looking for a new house.
Our house is going to be demolished, because a new motorway is being built.

(3)
a. I must have a drink of water.
I feel thirsty.
b. I have to have a drink of water.
The doctor has told me to drink more water.

(4)
a. I really must do something about the garden.
I feel I should tidy up the garden.
b. I have to do something about the garden.
The local authority have warned me to tidy my garden.

(5)
a. We must do something about the dog.
We must look after our dog better.
b. We have to do something about our dog.
The police have warned us that if we don't control our dog better, they will
take it away.

(6)
a. We must do something about terrorism.
I feel strongly that something ought to be done.
b. We have to do something about terrorism.
Unless we do something quickly, there will be a disaster. Every country in
the world agrees about this.

(7)
a. It must be right.
I think it is right from what I can see.
b. It has to be right.
We cannot finish it until it is totally clear that it is right.
(8)
a. You must wear a tie.
I think you should wear a tie.
b. You have to wear a tie.
They won't let you in unless you wear a tie.

(9)
a. We must be there by 4.
I think all the seats will be taken by 4.
b. We have to be there by 4.
The doors are closed at 4 o'clock.


I feel comfortable with 4a. because of “really”.
I don’t detect any difference between “must” and “have to” in 4b.
I feel comfortable with either 7a. (deduction) and 7b.
As for the remaining sentences, I do not perceive any difference between “must” and “have to”. Am I correct?
Thanks a lot.
WW

 

[Tdol]

I think those distinctions could be made, but I wouldn't say that everyone makes them. I think that they are often used interchangeably, so with the first, for example, someone could use must for the external obligation or have to for the internal one, and the addition of really in #4 is common.

 

[Walt Whitman]

Thank you Tdol for your time in reading my long post!
Maybe off topic but I must say that it makes me uncomfortable when students of English (and English teachers as well) are asked to make choices (if they want to pass their exams) on the basis of rules which do not “exist” for most native speakers of English. I am perfectly aware that a lot of rules are designed to make the language more manageable for learners. However, we shouldn’t forget that these rules are often gross simplifications of reality and can’t always be considered standard English (see Tdol’s words, “I think that they [“must” and “have to”] are often used interchangeably.”).To cut a long story short, do you think it is fair to fail an exam only because the setter’s expected answer is not the one given by the examinee? Not even a native would ever give the expected answer. This is the kind of thing that drives me crazy.Anyone here willing to share what they think?
WW

 

[Tdol]

No- no one should fail an exam or even lose a point because their correct answer is different from the setter's expected one. You'd hope that the marker would see to that, but sometimes people do stick rigidly to a narrow list of correct answers.