Using "must" to express probability with high degree of certainty



The army often just can't tell who the Taliban are, and whoever dreamed up these hare-brained interviews must not have seen the extensive media coverage of "collateral damage" in 2012.

As far as I understand from the context, the journalist uses "must" as if s/he is pretty certain that those who dreamed up have not seen the extensive media coverage of "collateral damage" in 2012. (Sorry for the terrible wording!)

Is it common to use "must" in this way? Is there an alternative form to express the same meaning, perhaps using "might"?


Posted 2013-03-11T18:37:10.010


The only one to me that implies absolute certainty is "didn't see". – BobRodes – 2013-06-29T07:30:58.893


Yes, it's common. See sense 5b in the AHD. I can't think of a good paraphrase off the top of my head, so I can't answer just yet, but I'm not sure it's possible to use might here. I don't think might is certain enough.

– snailplane – 2013-03-11T18:51:48.120

2@Carlo: If you substitute "might", you're [potentially radically] changing the meaning. As it stands, the writer is certain of what he says. With "might", he'd only be advancing a possible explanation (which he could then go on to dismiss as something he doesn't actually believe anyway). – FumbleFingers Reinstate Monica – 2013-03-11T19:07:39.460

1might is impossible, but cannot have seen works. – StoneyB on hiatus – 2013-03-11T21:32:29.253



Yes, this is a valid use - it is used to imply a deduction:

I see that the window is open and my TV is missing, so I must have been robbed.

If the lights were on, they must've been home.

Inevitably we all must die.


Posted 2013-03-11T18:37:10.010

Reputation: 11 728

I agree with the sense of deduction in the first two sentences in your answer, but not the third one. – Jason S – 2014-11-09T16:05:35.587