Il n'a pas l'air bien. Il a dû trop boire la nuit dernière.

Sentence Discussions French
#1
English Translation

He doesn’t look well. He must have drunk too much last night.

Should boire be bu? I can’t find anything that supports the use of the infinitive in this context.

#2

The way I see it, after “a dû” you can’t use a finite form like bu; you must use an infinitive.

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#3

so “il a dû boire“ can mean either
He had to drink OR
He must have been drinking
?
I just couldn’t find it as a rule or example anywhere. All the examples define it as the infinitive: He had to drink

#4

If I change the verb, some examples come up with a translation in the past tense but I still don’t find a rule or explanation anywhere as this being a place where you use the infinitive. Thank you for the answer.

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#5

Hi @corgwin24,

“Devoir” is just one of these verbs that can be used in many many different ways, one of which being: “devoir + infinitif”.

I wouldn’t get hung up on tenses here. I think the most important thing is to know what you can express with this construction. The basic meanings are:

obligation / necessity:

  • Vous devez respecter la loi (i.e otherwise you may end up in jail)

  • Les élèves doivent écouter leur professeur (otherwise they get expelled)

  • Ils ont dû évacuer le bâtiment à cause de l’incendie (necessary, not to die)

  • Il devra faire mieux au 3e trimestre pour éviter le redoublement.

high probability:

  • Il doit être très triste (he nust be very sad)

  • Il a dû être très déçu (he must have been very disappointed)

  • Il a dû trop boire la nuit dernière.

As often, context matters :

Depending on context, Il a dû partir could be translated as:

  • He had to leave (He got a call / family emergency → he’s gone)
  • He must have left (I can’t see him/find him anywhere → high probability that he’s gone)
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