Grammar: Indirect Question
In English, indirect question follows some complex rules regarding sequence
of tense (although if you are a native speaker of English, you are not
consciously aware of how complicated those rules are: lucky for you!)
How long does the film last?
I asked him how long the film lasted.
Why do they live in such a small house?
We didn't want to know why they lived in such a small house.
Who ate the last piece of cake?
I told them who had eaten the last piece of cake.
In Latin, a different construction is used: an indirect question also uses the subjunctive. The choice of the subjunctive follows rules for sequence of tense. In other words, the tense of the subjunctive is determined
by the tense of the main verb: if the main verb is in the present or future, this is called "primary" sequence of tense; if the main verb is in the past, this is called "secondary" sequence of tense. If you are dealing with primary sequence of tense, you use the present subjunctive for action simultaneous with or subsequent to the main verb; for action prior to the main verb, you use the perfect subjunctive. If you are dealing with secondary sequence of tense, you use the imperfect subjunctive for action simultaneous with or subsequent to the main verb; for action prior to the main verb, you use the pluperfect subjunctive.
Here are some examples:
Primary - present subjunctive.
Quid facit ille? Nescio. ("What is that man doing?" I don't know.)
Nescio quid ille faciat. (I don't know what that man is doing.)
(the man is doing something at the same time as my not knowing)
Primary - perfect subjunctive.
Quid viderunt mulieres? Exponam. ("What did the women see?" I will
Exponam quid viderint mulieres. (I will explain what the women
(the women saw something in past, prior to my explaining)
Secondary - imperfect subjunctive.
Quid optant? Omnes dixerunt. ("What do they want?" Everybody said.)
Omnes dixerunt quid optarent. (Everybody said what they wanted.)
(everybody wants something, at the same time as they were speaking)
Secondary - pluperfect subjunctive.
Quis pecuniam perdidit? Marcus rogavit. ("Who lost the money?" Marcus
Marcus rogavit quis pecuniam perdidisset. (Marcus asked who lost
(somebody lost the money prior to Marcus asking about it)