We know that 'must' is used to show obligation, deduction,strong recommendation and also for certainty.

She must be going to the market.(certainty/deduction)

He must study to pass the exam.(obligation/strong recommendation)

Now my question is can we use must+V1 to show certainty? For example, if I want to say that Ram is very brilliant boy and it is very certain that he reads all the day , can I say

He must read all the day (to show certainty) ?

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    Yes. She is a very good athlete. She must train a lot. Aug 13, 2022 at 9:20
  • @MichaelHarvey ok I got it. Now can use must for future certainty? If I want to say that he will obviously go, can I say "he must go" ? Aug 13, 2022 at 9:46
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    You can't deduce from something that hasn't happened yet. Aug 13, 2022 at 10:02
  • Ok. Now if someone says " he must work very hard" , which meaning is to choose? It's obligatory for him to work hard or it's certain that he works hard? I think that depends on the context. Right? Aug 13, 2022 at 10:09
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    It's absolutely all about context. It is not always sensible to consider text in isolation. Compare: "He must work very hard because he always looks tired", and "He must work very hard if he is to complete his project by next Tuesday" Aug 13, 2022 at 10:46

1 Answer 1


Yes. Modals usually have an epistemic reading (showing the quality of the speaker's knowledge or certainty) as well as their normal deontic reading, and the epistemic reading of must is a conclusion of certainty.

See Must, sense 3 in Wikitionary

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