[7] Apart from the types mentioned below it is also possible to have mixed conditionals, for example with different tenses in protasis and apodosis.
It is frequently used by Cicero as well as other writers:[89] An ideal condition can occur in a past context also, in which case it uses the imperfect subjunctive.
[144] This is common in contexts such as 'go to see if', 'try to see if' and 'wait to see if': In the following example, the present indicative is used: However, in most such sentences, since there is some idea of purpose, the subjunctive mood is used.
However, occasionally in poetry a wish may be expressed with ō sī... followed by a subjunctive mood verb.
The construction is described by Gildersleeve & Lodge as 'poetical and very rare':[151] Subordinate clauses in indirect speech usually use the subjunctive mood.
[177] The imperfect subjunctive in the protasis remains unchanged, even after a primary tense verb: In the following, a present unreal situation follows from an unreal past condition: If the apodosis is an indirect question, the future participle is combined with the perfect subjunctive fuerit instead of the perfect infinitive fuisse:[183] In an indirect past unreal conditional, the apodosis is also often expressed using the future participle plus fuisse, exactly as a present unreal conditional:[185] When the indirect speech is an indirect question, or a quīn clause, rather than an indirect statement, the construction in the apodosis is the same, except that the perfect infinitive fuisse is replaced by the perfect subjunctive fuerit: When the verb is passive, futūrum fuisse ut can occasionally be used.
[190] However, this is very rare, and only two instances have been noted:[191] Another way of expressing a passive verb in the apodosis of an unreal conditional in indirect speech is to use the perfect infinitive of possum combined with a present passive infinitive; that is, to write 'could have been done' instead of 'would have been done', since the two are close in meaning:[183] Similarly in an indirect question, the perfect subjunctive potuerit with the present infinitive can be used: Another possibility, when the main verb in a quīn-clause is passive, is for the tense to be unchanged from direct speech.
Thus in the following, the pluperfect subjunctive is retained:[195] Even after a historic introductory verb, the perfect subjunctive is usually still retained in a quīn clause (contrary to the usual sequence of tenses rule):[195] Exactly the same sequence of tenses is used if the conditional sentence is part of a consecutive clause instead of a quī-clause:[195] Similarly the perfect subjunctive potuerit, not the pluperfect potuisset, is also usually used even after an historic-tense introductory verb to express a passive verb: Occasionally, however, after a historic verb the pluperfect subjunctive fuisset is used, but this is rare, and found only in Livy:[195] The following example is unusual in that it envisages a future event that might one day have taken place if a past situation had been different.
The tense used in the apodosis is the imperfect subjunctive:[201] In classical Latin, indirect questions are almost never introduced by sī.
Instead, after the verb quaerō 'I ask', the simple suffix -ne is usually used: However, Livy sometimes uses sī:[204] According to Lewis and Short's dictionary,[206] this usage derives from the meaning 'to see if by chance' described above.
A sentence where this meaning after quaerō is more evident is the following: Another place where 'if' is used in modern languages is in expressions such as 'I don't know if ...'.