As far as I understand, the construction must + present perfect is used to make presumptions about past events with the connection to the present:

Look, somebody must've been here - the stove is still warm.

But what about narration which is put in past simple? Can I use the same construction like this:

When I woke up and cast a glance on the ceiling, it must have been the early morning.

Is it correct?

  • Must + infinitive perfect is used for assumptions about the past with a high probability.
    – rogermue
    Aug 17, 2015 at 7:26
  • @rogermue But can it be used in this context, that is in past time narration?
    – olegst
    Aug 17, 2015 at 7:54
  • If you use direct speech in your narration I don't see any problem.
    – rogermue
    Aug 17, 2015 at 10:02

2 Answers 2


I have just come across this with a language student; they had just covered the rule that you cannot use "must" in the past, then we came across "I must have forgotten to water the plants". I had to find an explanation to this dilemma and it highlights the importance of teaching in context.

  • "Must" in case one is used for obligation: "I must wear a uniform" and you cannot construct the sentence with the past simple, here you would substitute "must" for "had to"

  • "Must" in case two is used to express a presumption about the past and uses the present perfect and conveys a past action that relates to the present or a later past event in narratives.


When I woke up and cast a glance at the ceiling, it must have been the early morning

is not working for me. How about something like this instead:

I woke up and cast a glance at the ceiling. Judging from the pattern of light and shadow, I thought it must still be early, probably around 6 or 6:30.

  • 3
    So, you have just taken her simple and clear sentence and over complicated it. Is there a word for a person who edits in the opposite direction by making things less clear? Aug 19, 2015 at 0:33

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