I want to state an opinion:
I've bought three loaves- that should/must be enough.
My grammar book says:
Must : Deduction ( deciding that something is certain)
- > I think that when using must for a deduction, the speaker is certain about their deduction.
Should: Deduction (deciding that something is probable)
- > I think that when using should for a deduction, the speaker is less certain about their deduction.
So that,I think both sentences are good to use, but there is a slight difference in the meaning
...that must be enough.
=> The speaker shows great certainty in his opinion.
...that should be enough.
=> The speaker shows a less degree of certainty in his opinion.
Are my opinions correct?
LE HANH 2383My grammar book says:
Must : Deduction ( deciding that something is certain)
- > I think that when using must for a deduction, the speaker is certain about their deduction.
Should: Deduction (deciding that something is probable)
- > I think that when using should for a deduction, the speaker is less certain about their deduction.
Your grammar book is consistently steering you in wrong directions, especially with its obsession with certainty and uncertainty.
that must be enough = the only logical conclusion is that that is enough
that should be enough = I expect that will be enough
Examples with the same meanings:
must
If you say so, it must be true.
That diamond is huge. It must be incredibly expensive.
She has won prizes both for her paintings and for her poetry. That must be a very difficult thing to do.
should
A lot of celebrities will be in the play. It should be a good show.
My car battery went dead. I think I'll go to Acme Motors. They should be able to replace it quickly.
What do you mean you lost your key? If you left it on the kitchen table, it should still be there.
CJ
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Comments
Thank you, CJ.
I have other situations:
Both should/must can be used. Right?
he must be well over 50.= the only logical conclusion is that he is over 50.
he should be well over 50. = I expect that he is over 50.
Both should/must can be used. Right?
They must be having a party. = the only logical conclusion is that they are having a party.
They should be having a party.= I expect that they are having a party.
Yes, with a slightly different meaning, but very similar in this case of guessing age.
'should' may be possible in this context in British English (I don't know), but we Americans don't use 'should' that way. If we hear the loud music, we say that there must be a party, not that there should be a party. In American English, they should be having a party means that it is advisable (a good idea) for them to be having a party, which is very different.
CJ
Can I replace "must" into "should" with the meaning that I expect it is very expensive. ?
Talking about "should":
There are some contexts, as in "I've bought three loaves- that should/must be enough, "should" can be understood as expectation ( I expect that it is enough).
But there are some contexts, as in "They should/must be having a party", "should" can be understood as "it is a good thing to do". In this context, "should be can not be understood as I expect they are having. Can you explain for me the reason?
It doesn't sound right to me. No. I would not say that.
No. I'm afraid I cannot explain when it means 'I expect that' and when it means 'It's a good idea'. I have been looking for an answer to that question for years — an answer that even beginners in English can understand. But I haven't found anything yet that even native speakers can understand. There may be an answer in some linguistics article somewhere, but I've never researched the question that deeply because it rarely comes up. In fact, you are the first person who has asked.
If I am struck by some genius thought that explains it all, I will get back to you on this.
CJ
The use of modal verbs for deduction is confusing. Sometimes, I don't know how to choose a correct one to use, especially between "should" and "must"
There are some situations, both can be used without much difference as in " I've bought three loaves- that should/must be enough."
There are some situations, only one of them can be used, as in "That diamond is huge. It must be incredibly expensive." or "They must be having a party".
I have another special context where all modal verbs can be used without much difference:
(1) It will be John. -> I strongly believe that is John.
(2) It could/ may/might be John. -> It is possible that is John
(3) It must be John- >Among my friends, John often visits my home at this time, so that I deduct that is John.
(4) It should be John- >Among my friends, John often visits my home at this time, so that I expect that is John.
(5) It would be John-> I even have heard this sentence in a movie.
I made all the explanations above by myself based on what I learnt. I don't know if native speakers also have the same idea.
I wish I didn't have these kinds of questions. That would be easy for me in learning English process.
If I choose a wrong modal verb for a deduction, is that a big problem? Do native speakers still understand what I mean?
Modals are a rather advanced topic in English, so it may take a while to get used to them.
Note that I don't think of 'should' as a verb of deduction. In the usage that we have been discussing in this thread, I think of it as a verb of expectation. Deduction is much more definite. There can't be any other answer, and it's not personal. That is, it's more like a mathematical truth. (It must be enough. — It has to be the case that it is enough.) Expectation is more like a guess. (It should be enough. — I guess/think/suppose it's enough.) And expectation is personal. It's expressed more like the speaker's opinion, not an objective truth.
That depends on the specific error. In many cases you will still be understood, but in many other cases the wrong modal verb can lead to misunderstandings.
CJ
CalifJimNote that I don't think of 'should' as a verb of deduction. In the usage that we have been discussing in this thread, I think of it as a verb of expectation. Deduction is much more definite. There can't be any other answer, and it's not personal. That is, it's more like a mathematical truth. (It must be enough. — It has to be the case that it is enough.) Expectation is more like a guess. (It should be enough. — I guess/think/suppose it's enough.) And expectation is personal. It's expressed more like the speaker's opinion, not an objective truth.
Thank you CJ. This explanation is useful and makes sense to me.
Let see, my grammar book still calls "should" as deduction:
To you and all member on this form. Thank you for always always being by my side to help me with strange questions.