Past, past perfect, and present perfect

[rajeshmalladi]

Could you please explain which of the following sentences are possible.

They left because it snowed.
They left because it has snowed.
They left because it had snowed.

They have left because it snowed.
They have left because it has snowed.
They have left because it had snowed.

They had left because it snowed.
They had left because it has snowed.
They had left because it had snowed.

Kindly explain all sentences atleast briefly so that they will never be any doubt regarding those combinations again.

[Pete]

>Could you please explain which of the following sentences are possible.

>They left because it snowed. [Ok. It might mean that it snowed and they left immediately, and it might mean the same thing as the third sentence.]
>They left because it has snowed. [Ok, but the snowing and leaving took place quite recently. The snow is probably still having an effect as you describe it.]
>They left because it had snowed. [Ok. Definitely says that it snowed earlier and then they left.]

>They have left because it snowed. [Ok. You would use present perfect if the leaving was recent and has some particular importance in the present circumstances.]
>They have left because it has snowed. [Ok. I don't think there is any difference in meaning from the preceding sentence.]
>They have left because it had snowed. [No. There is no past tense involved, so past perfect sounds wrong.]

>They had left because it snowed. [The past perfect here only makes sense in a context where some other past action is already being discussed, and you are emphasizing that the leaving took place before that action.]
>They had left because it has snowed. [No. There is no past tense involved, so the past perfect doesn't fit.]
>They had left because it had snowed. [The same consideration applies as in the first sentence of this group. The past perfect in the second clause is better than the simple past, but the simple past (as in the earlier example) can be substituted for the past perfect since the time order of the actions is clear.]

>Kindly explain all sentences at least briefly so that they will never be any doubt regarding those combinations again.
-- Somehow I don't think that these brief comments of mine will resolve all your questions about these tenses. :)