Must have told vs should have told

9

4

A: "Why are you so mad?"
B: "You ...... me you weren't coming to dinner. I waited for you for two hours "

The answer is " should have told " and I can understand why but there was another option on the test that " must have told "..I was just wondering is there any possibility we can use " "must have told" here on the blank to stress our emotions/feeling in order to make it clear that I detest to have been waited for..

Thanks

Mrt

Posted 2014-11-11T17:25:52.100

Reputation: 10 254

Question was closed 2014-11-12T06:53:11.297

Answers

14

You should have told me you weren't coming to dinner. I waited for two hours.

As you noted, this construction indicates dissapointment that an act was not performed.

You must have told me you weren't coming to dinner.

This construction is used to assert that something happened in the past when the evidence is incomplete.

  • I don't know why I decided to take my book with me. You must have told me you weren't coming to dinner, but I don't remember it at all. Nonetheless, I am glad I had something to read.
  • We don't know why Daisy Duck became a singer. Her mother must have told her that she had a nice voice.
  • I didn't put the presents under the tree or eat that cookie. Santa Claus must have come down the chimney last night

Adam

Posted 2014-11-11T17:25:52.100

Reputation: 8 151

2Thank you ADAM for your nice examples.The second example of sentence is pretty tricky that I thought it was wrong but I got it now.It makes the difference clear. – Mrt – 2014-11-11T18:13:06.470

7

Must have been here expresses logical necessity, not obligation.

Here's an example of the use of must have been:

A: Why are you so mad?
B: "You must have been crazy for not coming to dinner. The food was delicious!
(Meaning: I believe that only a crazy person would've avoided such a delicious dinner)

OR:

A: Why are you so mad?
B: "You must have told me you weren't coming to dinner, but I forgot this and waited for you for two hours like a fool.
(Meaning: I know that my memory is poor. This is why I believe that you had told me that you weren't coming to dinner, but I forgot this.)

Sense the difference:

You must do as I tell you.
(Meaning: You are obligated to do as I tell you)

But

You must have done as I told you.
(Meaning: Judging by the available information, I believe you have done as I told you).

One more example, from a song by Roxette:

It must have been love
But it's over now

The meaning is: There was a feeling between us. I believe this feeling was love. But whatever it was, it no longer exists.

Let's remodel using should have been:

It should have been love
But it's over now

The meaning is: There was a feeling between us. It was definitely not love. I wish it were love. Anyway, it no longer exists.

CowperKettle

Posted 2014-11-11T17:25:52.100

Reputation: 36 949

2Thank you Copperkettle.I can understand what you mean.Briefly what I understood is that while the present form of the word must is related to obligatory or strong suggestions , its past form is related to strong possibility.. – Mrt – 2014-11-11T18:02:22.587

2Yes, @Murat, you're right. Modal verbs are tricky. English grammarians must have made them tricky on purpose to confuse non-natives. (0: – CowperKettle – 2014-11-11T18:03:21.957

3

You must have told me you weren't coming to dinner.

As some of the other, very good, answers say, when we read this sentence we understand must differently. We think that the speaker is using must to show that they have a good reason to believe that you told me you weren't coming to dinner is definitely true.

The Original Poster compares the must sentence with this should example:

You should have told me you weren't coming to dinner.

Here the speaker is saying that it was bad that you didn't tell them that you weren't coming. Here should is about obligation. When a speaker uses should like this, they are talking about what things are good things to do - or bad things to do.

I want to show why it is not possible to use must in the same way when we talk about the past. If you really understand how must works for obligations in the present and future, then you will understand why we can't use it about the past.

If we change the original example so that it is present or future time, we can use either must or should:

  • You should tell them you aren't going to dinner.
  • You must tell them you aren't going to dinner.

The first sentence with should says that it is a good thing to tell them that you aren't going for dinner. Who thinks it's a good thing? The speaker does. When the person speaking says should they are telling you about what they or somebody else says is the right thing to do. The second example is different. The speaker is saying that it is necessary to tell them you aren't going to dinner. Who says it's necessary? The speaker does.

Now necessary, means 100% necessary. This is very different from saying that something is a good idea. If I say something is a good idea, maybe I am persuading you to do that thing - but you don't have to do it. It's your decision. If I say "You should go to the doctor", I am not saying that you have to go. It's not necessary that you do this. I'm just telling you that it's a good idea. It's advice. You can choose what to do. But if your boss says You must be at work by 8.30 they are saying it is 100% necessary. You cannot choose. Who is saying it's necessary? The person speaking is. When someone says:

  • You must do X!

They are really saying:

  • Do X!

It is not a suggestion. Really, it is an order. Because of this there are some things we can't say with must, but we can say with should. For example, if you ask your boss, if you can come in late for work tomorrow, your boss might say:

  • Well you should always be here by 8.30, but you can come in late tomorrow, just this one time.

Here they are saying that it is better to be here at 8.30, but you can be a bit late tomorrow. They cannot say:

  • *You must always be here by 8.30, but you can be late tomorrow.

This doesn't make sense because You must be always be here by 8.30 means it is 100% necessary. It is like saying: Be here on time, but you can be late. It is contradictory. When you use the word must, you are saying it is 100% necessary. It means you don't even have any idea that this thing won't happen.

Now if we return the the Original Poster's example, it is clear that the speaker cannot use must:

  1. You should have told me you weren't coming to dinner.

  2. You must have told me you weren't coming to dinner.

We can use the first sentence, because we are saying that it would have been good to "tell them you weren't going to dinner". Who is saying it would have been a good idea? We are. But we can't say sentence 2 because we can't say "tell them in the past that you weren't coming to dinner". We can't say "I am telling you it is 100% necessary that you tell them". The situation is over, it happened in the past. We can't change it!

Because, when we read this sentence, we know that it can't be about a 100% necessary obligation in the past, we can only read it as an epistemic sentence - where must means I definitely know that "you told them you weren't coming to dinner".

Hope this is helpful!

Araucaria - Not here any more.

Posted 2014-11-11T17:25:52.100

Reputation: 25 536

1But we can say "It was your solemn duty to tell me", indicating an all-out necessity in the past. Frankly, I can make myself perceive must have in the sense of should have, like a person may make an optical illusion seem to rotate this or that way by the power of imagination. P.S. I think I understand why "must" loses its power. "You must have" in that sense would be like "you were obligated to", which is counterfactual. – CowperKettle – 2014-11-11T19:21:26.550

@CopperKettle Yes, exactly, the fact that it's counterfactual means we can't say that it's necessary to turn it into a reality! – Araucaria - Not here any more. – 2014-11-11T19:59:33.623