I am following English Grammar in Use by Raymond Murphy: unit 114 is about "in case".
The author mentioned the use of 2 tenses(present and past) with "in case":
Do not use will after "in case". Use a present tense for the future.
You can use in case + past to say why somebody did something.
Here are 2 examples of present tense given by the book:
- Your car should have a spare wheel in case you have a puncture.
- I'll remind them about the meeting in case they've forgotten.
And 2 examples of past tense:
- I left my phone switched on in case Jane called.
- We rang the doorbell again in case they hadn't heard it the first time.
I can understand examples about present simple and past simple, but I can't figure out the difference of choosing present simple and present perfect, and of choosing past simple and past perfect.
I know that 'perfect' describes something happened in the past and have/had effect on a certain moment(the current momenta or a moment in the past.)
I have problem to distinguish the difference in meaning in this case. What's the difference in meaning between "simple" and "perfect" in this case?
Thanks.
Best Answer
The use of the Perfect Tense in Conditional clauses depends on the chronology of the events.
If the chronology is incorrect we should use the Perfect Tense.
If the chronology is correct we should use the Simple Tense.
Compare your examples:
Present tense:
Your car should have a spare wheel in case you have a puncture.
(The problem with the wheel may follow the first event, not vice versa)
I'll remind them about the meeting in case they've forgotten.
(They may forget only before the meeting, not after)
Past tense:
I left my phone switched on in case Jane called.
(She will or won't call in future)
We rang the doorbell again in case they hadn't heard it the first time.
(They didn't or did hear, we didn't know, so we rang again)