We now touch a topic we don't want to touch at the moment, the sequence of tenses because we have dedicated a whole chapter (chapter 18) to it. But it is useless to explain that there are four different tenses in subjunctive without telling when and how they must be used. So we explain briefly how to use them. In chapter 18 we are going to talk about the sequence of tenses more in detail. There are four tenses in subjunctive.
congiuntivo
presente
imperfetto
passato prossimo
trapassato prossimo
io arrivi...
io arrivassi...
io sia arrivato...
io fossi arrivato...
io compri...
io comprassi...
io abbia comprato...
io avessi comprato...
The first thing we have to see is that the subjunctive is never (about the few exception we are going to talk soon) used alone. There is always an introductory sentence in presente, passato remoto, passato prossimo or trapassato prossimo which anchors the actions / events reported in the subordinate sentence in the timeline.
examples
Io temo che venga.
I am afraid that he comes.
Io temo che sia venuto.
I am afraid he has come.
Io temei (temevo) che venisse.
I was afraid he came.
Io temei (temevo) che fosse venuto.
I was afraid, that he had come.
Io ho temuto che venisse.*
I have been afraid that he come.
Io ho temuto che fosse venuto. *
I had been afraid that he had come.
* If you don' t speak Spanish, there is no problem at all. If you speak Spanish you have a problem. Yes, the sentences are right and yes, it doesn' t work as in Spanish. In nowadays Italian the passato prossimo is always considered as a time of the past, even in the regions where the passato prossimo has not assumed the functions of the passato prossimo. Therefore it is (a) Io ho temuto che venisse and not (b) Io ho temuto che venga. If the passato prossimo has not assumed the functions of the passato remoto (b) would be more logical, but that' s not the way it works. It doesn' t work as in Spanish. We are going to discuss about that later once again.
So let's see what is the problem. If someone is afraid of something it must be possible to make clear whether he fears something that happened before he fears is, if it is happening at the moment when he fears it or if he fears something that will eventually happen in the future. Let's see it again with another verb, which requires, in contrast to Spanish and French, the subjunctive / congiuntivo in Italian.
examples
Io credo che lui venga.
I think that he come.
Io credo che lui sia venuto.
I think that he has come.
Io credevo che lui venisse.
I thought that he would come.
Io credo che lui fosse venuto.
I thought that he had come.
The table below shows the whole system and every possibilities.
The introductory sentence is in present
present
conjunction
simultaneity / posteriority
future
anteriority
Credo
Voglio
Temi
Aspettamo
che
lui venga
lui capisca
lei dorma
lei sappia
voi compriate
loro conoscano
lui verrà
lui capirà
lei dormirà
lei saprà
voi comprate
loro conosceranno
siano andati
siate venuti
siano partiti
abbiano comprato
abbia conosciuto
abbiate scherzato
The introductory sentence is in imperfetto
imperfetto (past tense)
conjunction
simultaneity / posteriority
future form the perspective of the past
anteriority
Ero sicuro
Dubitavi
Bastava
Pensavamo
Speravate
che
lui venisse
lei comprasse
loro comprassero
tu sappessi
io comprassi
lui sarebbe venuto
lei avrebbe comprato
loro avrebbero comprato
tu avresti saputo
io avrei comprato
fossimo andati
fossimo partiti
fossero venuti
avessi conosciuto
avessimo comprato
aveste venduto
The introductory sentence is in passato remoto
Passato Remoto
conjunction
simultaneity / posteriority
future from the perspective of the past
anteriority
Mi sembrò
Ti vergognasti
Io preferii
Noi sperammo
Voi pensaste
Loro dubitarono
che
lui capisse
loro cercassero
lei fermasse
noi finissimo
io apprissi
loro volessero
lui avrebbe capito
loro avrebbero cercato
lei avrebbe fermato
noi avremmo finito
io avrei aperto
loro avrebbero voluto
fossimo partiti
foste andati
fosse arrivato
avessi capito
avessimo sofferto
aveste mangiato
example
present and simultaneity
Io credo che mangi troppo.
I think you eat too much.
present and future
Io credo che mangerai troppo. I think you will eat too mucht.
present and anteriority
Io credo che abbia mangiato troppo. I think that you have eaten too much.
past tense and simultaneity
Io credei / credevo che mangiassi troppo. I thought that you eat too much.
past tense and posteriority
Io credei / credevo che avresti mangiato troppo. I thought that you would eat too much.
past tense and anteriority
Io credei / credevo che avessi mangiato troppo. I thought that you had eaten too much.
The following tables show the system in a more systematic way.
present tenses
simultaneity / posteriority
anteriority
Presente
passato prossimo
congiuntivo presente
congiuntivo passato prossimo
past tenses
simultaneity / posteriority
anteriority
Imperfetto
Passato Remoto
congiuntivo imperfetto*
congiuntivo passato trapassato
* Actually it is a little bit more complicated. If it is important that the actions / events reported in the subordinate clause had happened after beeing reported (a future from a point of view in the past) it is possible as well in ITALIAN (not in Spanish) to use the condizionale II even if the introductory verb requires the congiuntivo.
Credevo che avrebbe telefonato.
I thought that he would call.