The past subjunctive is used for the same reasons as the present subjunctive: to express emotion, doubts, and uncertainty. There is a large variety of situations in which subjunctive is used, just as there are many different expressions that go along with them. Note that the only difference between the present subjunctive and the past subjunctive is tense; usage is the same for both.
Construction of the Past Subjunctive
The French past subjunctive is a compound conjugation, which means it has two parts:
- subjunctive of the auxiliary verb (either avoir or être)
- past participle of the main verb
Like all French compound conjugations, the past subjunctive may be subject to a grammatical agreement:
- When the auxiliary verb is être, the past participle must agree with the subject.
- When the auxiliary verb is avoir, the past participle may have to agree with its direct object.
Je ne crois pas, qu'il ait commencé ce travail. I don't think he started the job yet.
- Je ne crois pas = present tense
- il ait = subjunctive of avoir
- commencé = past participle of commencer
Il faut que vous soyez partis avant matin. You need to be gone before morning.
- Il faut que = present tense
- vous soyez = subjunctive of être
- partis= past participle of partir, in agreement with the subject vous
Usage of the Past Subjunctive
Le passé du subjonctif is used to express an uncertain action that supposedly happened before the moment of speaking. We employ it when the verb in the subordinate clause, the verb that follows que, happened before the verb in the main clause.
The past subjunctive can be used in a subordinate clause when the main clause is either in the present tense or the past tense.
When the Main Clause is in the Present Tense
- Je suis heureuse que tu sois venu hier. I'm happy that you came yesterday.
- Nous avons peur qu'il n'ait pas mangé. We're afraid that he didn't eat.
When the Main Clause is in the Past Tense
The past subjunctive may be also used in a subordinate clause when the main clause is in the past tense.
Note that if the meaning of the main clause did not call for the subjunctive and if the subordinate clause happened before the verb in the main clause, the subordinate clause would have been in plus-que-parfait (the past perfect). (See example below.) For this reason, the subordinate clause should technically be in plus-que-parfait subjonctif (the pluperfect subjunctive), but that is replaced by the past subjunctive in all but the most formal French.
An example of main clause-past perfect, subordinate clause-past perfect:
- Elle savait que je l'avais vue. She knew I had seen her.
Past subjunctive with main sentence in past tense:
- Il doutait que vous l'ayez vu. He doubted that you had seen it.
- J'avais peur qu'ils soient tombés. I was afraid that they had fallen.