Page 542 - Practical English Usage 3ed - Michael Swan, Oxford

should (2): obligation, deduction etc 519
4 if, in case, etc
Should can be used in if-clauses (see 261.1 for details), after in case (see 271.2), after for fear that and lest (see 321) and after so that and in order that (see 543).
Ifyou should see Caroline, tell her I've got the tickets.
I'll get a chicken out of the freezer in case Aunt Mary should come. He turned the radio down so that he shouldn't disturb the old lady.
5 I should/would; we should/would
Should can be used instead of would after I and we in certain cases. This
happens:
• in sentences with if (see 258.3)
If 1 had more time 1 should/would learn Japanese.
• in indirect speech (corresponding to shall/will in direct speech - see 275) 1 told her that we should/would be ready at B.OO. ('We shall/will be
ready ... :)
• and in 'future in the past' sentences (see 221).
1 looked at the house where 1 should/would spend the next three years.
519 should (2): obligation, deduction etc
1 obligation: Everybody should wear seat belts
We often use should to talk. about obligation, duty and similar ideas. It is less strong than must (see 520).
Everybody should wear car seat belts.
You shouldn't say things like that to Granny.
Applications should be sent before December 30th. (More polite than Applications must be sent . ..)
In questions, should is used to ask for advice or instructions, like a less definite fonn of shall (see 217).
Should 1 go and see the police, do you think? What should we do?
For the difference between should and had beuer. see 230.
2 probability: She should be back tomorrow
We can use should to say that we know something is probable (because it is logical or nonnal in the circumstances).
She's away, but she should be back tomorrow. (= I have good reasons to believe that she will be back tomorrow.)
Henry should get here soon - he left home at six.
We're spending the winter in Florida. ..., That should be nice.
3 past use: I knew that I should . ..; I was supposed to ...
Should is used unchanged in past indirect speech, if should was used in direct speech.
I thought '1 should write to Jane.' ..... 1 knew that 1 should write to Jane.
In other cases, should + infinitive is not nonnally used to talk. about the past. Instead, we can use for example was/were supposed to ... (see 572).
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