[Grammar] Why is "have to~" a modal?

[lydon]

Recently I bought some grammar books from amazon,
and it is written that "have to' is a modal. But this seems to have
no logic to me.

If it is a modal, why would we ever add [do] or [does] in order to make
a statement to a yes/no question such as,

I have to work -> Do you have to work?
They have to play soccer -> Do they have to play soccer?

Additionally, if this is a modal, I think [like to] [try to]...also have to be a modal too.

can some one give me a clear explanation?

 

[Nightmare85]

**Neither a teacher nor a native speaker.**

Hi lydon,
I had that question some months ago too

I have to work -> Do I have to work?
They have to play soccer -> Do they have to play soccer?
Yes, this is correct!
(At least for American English.)

The main difference is when you use it in negative sentences:
I have to work. -> I have not to work.
They have to play soccer. -> They have not to play soccer.

If you add a do in such a sentence, its meaning will be different:
I do not have to work. = I do not need to work. (Because I have enough money.)
They do not have to play soccer. = They do not need to play soccer. (Because they are good enough.)

It's also the case for negative questions:
Do I not have to work? -> Do I not need to work?
Do I have not to work?
(However, I'm not 100% sure here!!)

Cheers!

 

[lydon]

Well i'm not really sure whether the two example sentences you wrote make sense.

I have not to work.
They have not to work.

Do these sentences really make sense in American English?

Plus, as long as I know, [have to] means an obligation.
Therefore the opposite meaning shouldn't be "must not" but "not an obligation" which
means there are still possibilities to do it.

You don't have to work. (working is not an obligation but still, you may work)


here is a link : Modals - Have to (objective obligation)

 

[Nightmare85]

Well i'm not really sure whether the two example sentences you wrote make sense.

I have not to work.
They have not to work.

I have a job, and if I worked somewhere else it would be black labor.
So, I have not to work.

Of course "have not" is an obligation.

Cheers!

 

[lydon]

That's the point.

I think there was a confusion between the two words [negative] and [opposite].
We add the word "not" to make the sentence in a negative form not an opposite form.

In my opinion, the negative form of "obligation" is "not an obligation".

For example,

Affirmative → Negative
(1) I have to(obligation) → I don't have to(not an obligation)
(2) I have to(obligation) → I have not to (an obligation in the opposite meaning)

So,
(1) makes sense and is the negative form of [have to]
(2) makes sense but is not the negative form of [have to]



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