Elle avait fait ses devoirs avant qu’il n’arrive.

Question

I understand that avant que requires the subjunctive. Given that the first part of the sentence is in the pluperfect, why is the present subjunctive used rather than past subjunctive? His arrival is in the past, just not as far in the past as the homework.

Accepted Answer

Hi Heather, 
In fact, you will hear both in French.
In everyday spoken language, you will even drop the 'ne' -
Il avait fait ses devoirs avant qu'il arrive 
But you could say -
Il avait fait ses devoirs avant qu'il (ne) soit arrivé
which is more formal, 
or even in written form and very elevated language  :
Il avait fait ses devoirs avant qu'il (ne) fût arrivé ( subjunctive pluperfect) 
The important bit is to use the subjunctive.
Hope this helps!

Answer

In general the past subjunctive is only used when the action in the subordinate (i.e. subjunctive) clause precedes the main clause. It's the relationship to the main clause that is important, not whether it's in the past now. In the case of "avant que" , the main clause, by definition, must precede the subordinate clause, so I thought at first you would never use the past subjunctive.

But it turns out you can use it with "avant que", so its meaning here is a bit different. It seems that the choice of present or past subjunctive is more nuanced - you use the past subjunctive to indicate that the action is completed. This makes more sense with an action which takes some time to complete, for example:

Avant que nous mangions, nous étions à jeun. (i.e. as soon as we start eating we stop fasting)

Avant que nous ayons mangé, nous avions faim. (i.e. once we've finished eating we stop being hungry)

So if you think of arriving as instantaneous, then you probably wouldn't use the past subjunctive in your example. (Maybe it's still allowable to use it - I'm not sure - but it would be unnecessary.)