[Beatrix]

I have one more question. There is an example in Headway upper-Intermediate about the use of future tenses, and the sentence goes as follows:

`Your passports will be collected as you go through passport control`.

I wonder about the chunk of the sentence in bold. Why not "as you are going" or "as you will be going"? Why is not some Continuous form used here?

[susan53]

Two possibilities, which I think combine here :

1. If the continuous were used it would refer to the one moment of you personally passing through customs, whereas this is something that always happens to everyone. There's a sense of you being used impersonally here, so the simple form expresses the fact that is always true. Compare it with eg Keep stirring the mixture as you add the milk. In both this example and yours the continuous could be used, but it would give it a much more personal "one off" feel.

2. After a conjunction, the simple is always used used to refer to a future completed event. Examples :

When John arrives, call me.
As soon as the rain stops, we'll go out.
If you see Paul, let me know.
After the meeting finishes, we're going for a pizza.
As the course progresses, you'll find you understand more.
Unless you phone me, I'll expect you at six.

[Beatrix]

thanks susan! I don't have simple and continuous forms in my mother tongue, so that makes difficulties for me. I have free English lessons here, thanks again.

I have one more question, though.
Can you, please, clarify what you mean by
"After a conjunction, the simple is always used used to refer to a future completed event."
because that's exactly what was the problem here: the action is actually in progress, it's not completed. That's why I was wondering why some continuous form isn't used instead of present simple.
I think this example is a good equivalent to 'my' sentence:
"As the course progresses, you'll find you understand more."
but I don't see how the others are?

[susan53]

I think you'll find that in all of the sentences there is a sense of some completion. Eg As the course progresses ... by the time you understand more the course has already progressed to a certain point; As you pass through customs ... by the time your passport is checked you are already in customs. Thus in a sense the action is "complete".

But you're right that the action is still on-going - it's "complete" but not "finished". And that's why the continuous is also possible. With a sentence like As soon as the rain stops ... there's no alternative because the action is both complete and finished at the time you go out. But think about As you pass through customs ... In fact the sentence is nonsense because it doesn't mean you keep moving - the action is not, strictly speaking, on-going. You go into customs, stop and have your passport checked, and then go out again. So the use of the simple refers to refers to what the sentence really means - ie that you have already arrived in customs - rather than what it actually says - which doesn't stand up to literal analysis.

Combine this with the sense of "every time" which I referred to in explanation 1 and I think this is why, though both continuous and simple are possible, the simple would often be chosen.

[Beatrix]

thanks susan. I think this sense of "every time" is the best explanation. but, in fact, I think this is one of those things that you only have to memorize in order to know it in the future, because there aren't any real good explanations, really. at least that's how I learn such things. thanks again.

[susan53]

OK. But don't forget it's an alternative, not a "rule". You choose the verb form depending on the meaning it expresses and which you want to express too. It's always subjective.