Page 206 - DENG401_Advance Communication Skills

Unit 11: Conditional Sentences

Type III: Impossible conditional Notes

The condition didn't happen in the past, and so the result didn't happen either. It is used for
speculating about past events.
(a) If + Past perfect + Perfect conditional

If he had studied, he would have passed.
(b) If + Past perfect + might have
If someone had heard the S.O.S., their lives might have been saved
(c) If + Past perfect + could have (the meaning is could have been able to).

If my parent's hadn't been poor, I could have gone to university
Unless

Very often, unless can be used instead of if not. The meaning of unless is an exclusive one (only
if... not / except on condition that...) and it is normally used in sentences that say 'A will happen
if it is not stopped by B'.
Unless I find a good excuse (if I don't find a good excuse), my father will punish me.
I ‘II be back tomorrow unless there’s a plane strike (if there isn't a plane strike).
Let's have dinner out unless you're too tired (if you aren't too tired).

However, unless cannot be used in sentences that say 'A will result from B not happening.'
Compare:
I will be glad if she doesn't come this evening.

*l will be glad unless she comes this evening.
I will be surprised if she doesn't have an accident.
*l will be surprised unless she has an accident.

Notice

The main clause can come first and the if clause second, especially in questions.
What will he do if he fails his exams?

Inversion in Conditional Sentences

In literary style, we can sometimes omit if changing the word order subject / auxiliary. This has
nothing to do, of course, with an interrogative sentence.
If you should run into Peter Bellamy, tell him he owes me a letter. = Should you run into Peter
Bellamy...

If she were my daughter, I would send her to a boarding school. = Were she my daughter...
If war were to break out, I would emigrate to Mars. = Were war to break out...
If he had studied, he would have passed. = Had he studied...

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