[Conditional Comparisons.]
quasi (quam sī), tamquam sī, ut or velut sī.
[2117.] sī following a word meaning than or as is used with the subjunctive in conditional comparisons.
In this use, quasi (quam sī twice in Tacitus) and tamquam sī are found at all periods. ut sī is found in Terence once, in Cicero (not in the orations), once in Livy, sometimes in later writers. velut sī begins with Caesar; not in Cicero. ac sī is found once in the Bell. Hisp. and in late Latin.
[2118.] sī is often omitted after tamquam, and (from Livy on) sometimes after velut. After quasi it is sometimes inserted in Plautus, Lucretius, and late Latin. ceu is sometimes used, chiefly in poetry, for tamquam sī. The main clause often has as correlative ita, sīc, perinde, proinde, similiter, or nōn secus.
[2119.] The tense of the subjunctive is usually regulated by the sequence of tenses, in Cicero nearly always with quasi and tamquam sī.
quid mē sīc salūtās quasi dūdum nōn vīderīs? Pl. Am. 682, why dost thou greet me thus as if but now thou hadst not looked on me? quid ego hīs testibus ūtor, quasi rēs dubia sit? Caecil. 14, why do I employ these witnesses, as if it were a case involving doubt? tamquam sī claudus sim, cum fūstīst ambulandum, Pl. As. 427, I have to take my walks with a stick, as if I were a lame man. tamquam extrūderētur, ita cucurrit, Ph. 10, 10, he rushed away as if he had been kicked out. quod absentis Ariovistī crūdēlitātem, velut sī cōram adesset, horrērent, 1, 32, 4, because they trembled at Ariovistus’s barbarity, absent as he was, just as if he stood before their eyes. mē quoque iuvat, velut ipse in parte labōris ac perīculī fuerim, ad fīnem bellī Pūnicī pervēnisse, L. 31, 1, 1, I feel glad myself at having finally reached the end of the Punic war, as if I had had a direct hand in the work and the danger.
[2120.] The imperfect or pluperfect subjunctive is sometimes used, even when the leading verb is in a primary tense, to mark action more distinctly as non-occurrent ([2091]): as,
eius negōtium sīc velim suscipiās, ut sī esset rēs mea, Fam. 2, 14, I wish you would undertake his business, just as if it were my own affair. mē audiās, precor, tamquam sī mihī̆ quirītantī intervēnissēs, L. 40, 9, 7, listen to me, I pray you, as if you had come at a cry from me for help. iūs iūrandum perinde aestimandum quam sī Iovem fefellisset, Ta. 1, 73, as for the oath, it must be counted exactly as if he had broken one sworn on the name of Jupiter. This is the more usual way in Cicero with ut sī.