# FR: devoir / pouvoir - négation



## beginner-questions

Bonjour,

I was asking myself if there exists the same usage of devoir and pouvoir in its negation as in English.

I mean:
devoir = to must/ to have to
pouvoir = to be allowed to/ to have the permission

if you use it with 'ne pas' is this translation correct?:
ne devoir pas = don't have to/ it is not necesarry

and for:
ne pouvoir pas = don't be allowed to/ don't have the permission

or is it like in English?
ne devoir pas = don't be allowed to/ don't have the permission
what is than the correct meaning of 'ne pouvoir pas'

or do this modal verbes have in French a completly diffrent usage and meaning?

hope you can clear up my mind a bit


----------



## snarkhunter

Hello,

I do not know of any French verb that could not be used in both the affirmative and negative forms.

But the proper structure is "ne pas pouvoir / ne pas devoir". This is nothing specific to these verbs, though: Any negative form should be constructed this way.

_pouvoir / *ne pas* pouvoir
finir / *ne pas* finir
aimer / *ne pas* aimer_
etc.


----------



## beginner-questions

Hello  and thank you for the correction. but I am still not sure what they mean and how they are used. are they used as I thought or is it like in English that the negative form of 'devoir' gets a different meaning than the positiv?

so is devoir: you have to
and ne pas devoir: you don't have to (it's not necessary)
or does ne pas devoir mean: you are not allowed to (you don't have the permission to)


----------



## snarkhunter

Ha! Now I understand much better...

Actually, it can mean both, although the main sense is still "don't have to / must not".
As often, a matter of _context_. But I believe it would be more or less the same in English.


----------



## beginner-questions

ok, now I am a bit confused, because 'you don't have to' (it is not necessary to do it) and 'must not' (you don't have the permission) are not the same in English.
to get it clear.. in French 'ne pas devoir' can mean 'it is not necessary to do it' and 'you don't have the permission' - depending on the context. Is that right? And the main sense of 'ne pas devoir' is: don't have the permission to do it. ?

and what about (ne pas) pouvoir? has it only one meaning?
pouvoir = to have the permission
ne pas pouvoir = don't have the permission
or has it also other meanings?


----------



## snarkhunter

Yes, you're right: This structure has a dual meaning in French.

"ne pas pouvoir" = _not being allowed to_ and _not being able to_


----------



## beginner-questions

Parfait  Merci beaucoup. I think I know now how to use it..


----------



## snarkhunter

You're welcome. But please note that this is much _context-dependant_ and you cannot decide which of the two meanings one should actually understand in your sentence.


----------



## Oddmania

beginner-questions said:


> to get it clear.. in French 'ne pas devoir' can mean 'it is not necessary to do it' and 'you don't have the permission' - depending on the context. Is that right?



Hi,

No, it doesn't work that way in French! _Tu ne dois pas_ only means *You must not*, never _You don't have to_. 

"You don't have to" would be _Tu n'as pas à..._ in French. This is the verb _avoir à_ (which literally means "to have to"!). You could also say _Tu n'as pas besoin de..._ ("You don't need to...")

As for the verb _pouvoir_, _"Je ne peux pas..."_ may mean both _I can't_ (not able to) and _I may not_ (not allowed to).


----------



## beginner-questions

Hi, now I am confused again.. So I'll try it again.. 

_'ne pas devoir'_ and _'ne pas pouvoir'_ can both mean: not have the permission to do something.

to express in French that something is not necessary _'ne pas avoir à'_ is used or_ 'ne pas besoin de'_.

Did I understand it now right?


----------



## Oddmania

beginner-questions said:


> Hi, now I am confused again.. So I'll try it again..
> 
> _'ne pas devoir'_ and _'ne pas pouvoir'_ can both mean: not have the permission to do something.



Yes, but _devoir _is definitely stronger than _pouvoir_. For instance, _Tu ne dois pas fumer ici_ ("You must not smoke in here") is much more agressive/stronger than _Tu ne peux pas fumer ici_ ("You can't smoke in here")



beginner-questions said:


> to express in French that something is not necessary _'ne pas avoir à'_ is used or_ 'ne pas *avoir *besoin de'_.Did I understand it now right?


----------



## beginner-questions

merci beaucoup 
one more question due to the difference which you call "stronger".. does stronger also mean that "_Tu ne dois pas fumer ici!" _is a prohibition (like a law) and "_Tu ne peux pas fumer ici." _is more like morally forbidden (like you shouldn't do that)?


----------



## Oddmania

Exactly  Just like _mustn't_ and _can't_ in English.


----------



## zwim

There is a weaker meaning to _ne pas devoir_, which is _not supposed to, _a weak form of shouldn't.
It is explicit when used with _normalement,_ if the adverb (or something equivalent) is not used then it is context dependant, you have to guess.

_- Normallement tu ne dois pas écrire sur le côté droit de la carte postale. _

You won't go in jail if you write on the right side of the postcard, and your postcard will be delivered anyway, but you are not supposed to.

There is also another meaning which assimilates devoir to pouvoir, and thus in the negation leads to_ not be able to_

- _Tu ne dois pas comprendre grand chose à ce qu'il raconte._

Of course, it is neither an interdiction, nor any kind of restriction, just the fact that you are not able to understand him given the circumstances.

And to conclude there is also a stronger form of _ne pas pouvoir_, which is really an interdiction.

_- Je suis homosexuel, je ne peux pas donner mon sang.  --> i can't give my blood_

You can see clearly in this last example that it is the context (there is a law in France to forbid this), which gives the stronger meaning to pouvoir. 

It is different from :
_- Le mois dernier j'ai été malade, je ne peux pas donner mon sang.  --> i prefer not to give my blood
_
Here, you are restricting yourself because you think you are not able to (still too weak), or because you think it is not morally acceptable (maybe there is a risk for the receiver), although legally you could (i don't know the precise delay, but you get the idea).


----------



## Reynald

beginner-questions said:


> to express in French that something is not necessary _'ne pas avoir à'_ is used or_ 'ne pas besoin de'_.


Tu n'as pas besoin de... Tu n'es pas obligé de...

Pour résumer :

You must do it (obligation de faire) --> FR : Tu dois le faire

You must not do it (obligation de ne pas faire) --> FR : Tu ne dois pas le faire

You don't have to do it (non-obligation de faire) --> FR : Tu n'es pas obligé de le faire (tu peux. C'est comme tu veux).


----------

