Il faut or devoir?

Question

Hi, to say “I must” is there a difference between when one would use ‘Il faut que je …” instead of “je dois”? Or are they equivalent? (I believe devoir is simply followed by an infinitive rather than by the subjunctive with falloir, so it’s simpler to use!)  Thanks.

Accepted Answer

Hi Stephen, 
I don't quite agree with the answers below so will give my slant on it.
There is a difference between 'devoir' (obligation) and 'falloir' (nécessité) -

Je dois passer à la banque ce matin = I have to go to the bank this morning 
(You probably will but it's not a necessity).
Il faut que je passe à la banque ce matin = I need to go to the bank this morning
(You need some cash or you need to speak to them but 'it's imperative' that you do so.)

I don't like 'il faut que' translated by 'it is necessary' as it doesn't sound very English to me and often the need to do something will be conveyed by stressing the expression HAVE TO ( like in caps in written form.
I do like this page, however -
devoir/falloir
 
Hope this helps but happy to discuss further...

Answer

Bonjour Stephen,It is a matter of context always.Devoir can suggest a debt or a moral obligation depending on the context.Il faut que takes a meaning of necessity in the sense of "must" and this is why it is followed by the subjunctive mood.https://www.lawlessfrench.com/grammar/devoir-vs-falloir/The above link will explain further.Hope this helpsBonne journéeJim

Answer

Je dois faire des courses. -- I have to go grocery shopping. (Now)Il faut que je fasse des courses -- I must go grovery shopping (A more general statement)Both versions translate to the same sentence in English, but using devoir connotes a direct, concrete action, whereas falloir is more often used with general obligations. Maybe the English "it is necessary that..." captures the meaning of il faut que... better.