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In A Practical English Grammar A.J. Thomson and A.V. Martinet say that the past perfect is used after when when we wish to emphasize that the first action was completed before the second one started:

When he had shut the window we opened the door of the cage.

Is it preferred to "When he shut the window we opened the door of the cage"? Any difference in meaning?

When she had sung her song she sat down. ('When she sang her song she sat down' might give the impression that she sang seated.)

Do you agree with this?

He refused to go till he had seen all the pictures.

Before we had walked ten miles he complained of sore throat.

Here the above mentioned writers say that the action in the simple past precedes the action in the past perfect. Actually correct as it might be, this is weird, isn't it? Is this sequence (Conjunction + Past Perfect + Simple past)?

PS: Isn't it necessary to use commas when the conjunction is at the beginning of the sentence? Thanks in advance.
Comments  

When he had shut the window we opened the door of the cage.
Is it preferred to "When he shut the window we opened the door of the cage"? Any difference in meaning? -- Yes. Past perfect indicates that the window-shutting is finished first; past simple could mean that windoww-shutting and door-opening were simultaneous.

When she had sung her song she sat down. ('When she sang her song she sat down' might give the impression that she sang seated.) Do you agree with this? --Yes

He refused to go till he had seen all the pictures. Before we had walked ten miles he complained of sore throat.

Here the above mentioned writers say that the action in the simple past precedes the action in the past perfect. Actually correct as it might be, this is weird, isn't it? Is this sequence (Conjunction + Past Perfect + Simple past)? -- In the first sentence, going happens after seeing the pictures. The second is wierd, but in use. I forget why.

PS: Isn't it necessary to use commas when the conjunction is at the beginning of the sentence? Thanks in advance.-- Commas are generally called for, but not absolutely necessary with short and simple clauses.
Mister Micawber
When he had shut the window we opened the door of the cage.
Is it preferred to "When he shut the window we opened the door of the cage"? Any difference in meaning? -- Yes. Past perfect indicates that the window-shutting is finished first; past simple could mean that windoww-shutting and door-opening were simultaneous.

Hi, Mister Micawber. Thank you for your interest and answer.

A bit confusing though.

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He refused to go till he had seen all the pictures.
Before we had walked ten miles he complained of a sore throat.


In the first example the refusing comes first. Then (maybe) the seeing of all the pictures. Then (maybe) the (supposed, envisioned) going.

Yes, the action in the simple past precedes the (possible completion of the) action in the past perfect.
The seeing of all the pictures is a condition of going -- not a condition of refusing.
This is just a backshift of:
He refuses to go till he has seen all the pictures.
(That isn't problematic, is it?)
__________

In the second example the beginning of walking occurs first. Then the complaining. And then (maybe) the (supposed, envisioned) completion of the ten miles of walking.

Yes, the action in the simple past precedes the (possible completion of the) action in the past perfect.
This is an approximate backshift of:
Before we have walked ten miles he will complain of a sore throat.
__________

I agree with the authors about the time lines. It's not weird, no. The past perfect is not used exclusively to indicate the past of the past. The idea of "possible but uncertain completion" or other factors may enter into it.

CJ
Diamondrg, you're a very good questioner! I often learn from your questions!
The idea of "possible but uncertain completion" or other factors may enter into it.
I'd like to know more about this. Could you explain more about it?Emotion: smile
(1)When the lights went out, I lit some candles.
Diamondrg, let me try to answer your question. Please correct me if I'm wrong (very likely!).

In Sentence (1), "going out of the lights" and "lighting some candles" are opposite events. So, using "when" in the sense of sequence (not the simultaneous events) is naturally understood, and never be mistaken as simultaneous events.

Isn't that why?
Diamondrg, you're a very good questioner! I often learn from your questions!

The idea of "possible but uncertain completion" or other factors may enter into it.
I'd like to know more about this. Could you explain more about it?Emotion: smile
(1)When the lights went out, I lit some candles.
Diamondrg, let me try to answer your question. Please correct me if I'm wrong (very likely!).

In Sentence (1), "going out of the lights" and "lighting some candles" are opposite events. So, using "when" in the sense of sequence (not the simultaneous events) is naturally understood, and never be mistaken as simultaneous events.

Isn't that why?
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When he received his visa, he flew to Australia.
This sentence doesn't mean that his receiving his visa is done at the same time as flying to Australia. When the sequence is obvious, there's no need to think about past perfect [had received].

I have a question. What about Sentence (2) and (3)? Does either of these make sense?
(2) When I had entered the room, I found a cat.
(3) When I entered the room, I found a cat.