Wikipidia says, "The modal must expresses obligation or necessity: You must use this form; We must try to escape. It can also express a confident assumption (the epistemic rather than deontic use), such as in It must be here somewhere".

Then, isn't it true that "He must come back" can both mean "He has to come back" and "He will surely come back" ?

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    Note that many/most native speakers would pronounce the verb as hass (as well as place heavy stress on the word) in constructions like He has to come. Also note that both must and to have to can be "ambiguous" as to whether it''s the speaker and/or the person referred to who feels "under a compulsion" to do something. So He has to win might mean It's desperately important to me that he wins, because I placed a large bet on him. But it might mean He's very competitive, and can't bear losing (even if the speaker doesn't care one way or the other). Commented May 20, 2018 at 14:12
  • Thus, if you assume He has to come back means He will surely come back, you're looking at things from the speaker's perspective (the speaker is sure the other person will return, for whatever reason, and this is "necessary" for the speaker). But it could equally be used in contexts where it's the other person who will be compelled to return (speaker knows this to be the case, but doesn't necessarily care anyway). Commented May 20, 2018 at 14:17
  • I don't find the epistemic sense natural with future meaning. He must have come back is clearly epistemic: "I conclude that he has come back". But He must come back and he has to come back are only deontic for me.
    – Colin Fine
    Commented May 20, 2018 at 17:03

1 Answer 1


For the purpose of conveying a clearer picture, let's give a name to the guy - Tom.

"Tom must come back" also means "Tom has to come back".

However, "Tom will surely come back" does not mean either of those, because this sentence signifies the speaker knowing Tom's will (by choice), or lack thereof (by force).

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