2. Sī nōn (sī minus) is regularly employed:--

2. Sī nōn (sī minus) is regularly employed:--

a) When an apodosis with at, tamen, certē follows; as,--

dolōrem sī nōn potuerō frangere, tamen occultābō, _if I cannot crush my sorrow, yet I will hide it._

b) When an affirmative protasis is repeated in negative form; as,--

sī fēceris, magnam habēbō grātiam; sī nōn fēceris, ignōscam, _if you do it, I shall be deeply grateful; if you do not do it, I shall pardon you_.

a. But if the verb is omitted in the repetition, only si minus or sin minus is admissible; as,--

hōc sī assecūtus sum, gaudeō; sī minus, mē cōnsōlor, _if I have attained this, I am glad; if not, I console myself_.

3. Sīn. Where one protasis is followed by another opposed in meaning, but affirmative in form, the second is introduced by sīn; as,--

hunc mihi timōrem ēripe; sī vērus est, nē opprimar, sīn falsus, ut timēre dēsinam, _relieve me of this fear; if it is well founded, that I may not be destroyed; but if it is groundless, that I may cease to fear_.

4. Nisi has a fondness for combining with negatives (nōn, nēmō, nihil); as,--

nihil cōgitāvit nisi caedem, _he had no thought but murder_.

a. Nōn and nisi are always separated in the best Latinity.

5. Nisi forte, nisi vērō, nisi sī, _unless perchance, unless indeed_ (often with ironical force), take the Indicative; as,--

nisi vērō, quia perfecta rēs nōn est, nōn vidētur pūnienda, _unless indeed, because an act is not consummated, it does not seem to merit punishment_.

Conditional Clauses of Comparison.

307. 1. Conditional Clauses of Comparison are introduced by the particles, ac sī, ut sī, quasi, quam sī, tamquam sī, velut sī, or simply by velut or tamquam. They stand in the Subjunctive mood and regularly involve an ellipsis (see § 374, 1), as indicated in the following examples:--

tantus patrēs metus cēpit, velut sī jam ad portās hostis esset, _as great fear seized the senators as (would have seized them) if the enemy were already at the gates_;

sed quid ego hīs testibus ūtor quasi rēs dubia aut obscūra sit, _but why do I use these witnesses, as (I should do) if the matter were doubtful or obscure_;

serviam tibi tam quasi ēmerīs mē argentō, _I will serve you as though you had bought me for money_.

2. Note that in sentences of this kind the Latin observes the regular principles for the Sequence of Tenses. Thus after principal tenses the Latin uses the Present and Perfect (as in the second and third examples), where the English uses the Past and Past Perfect.

Concessive Clauses.

308. The term 'Concessive' is best restricted to those clauses developed from the Jussive Subjunctive which have the force of _granted that_, etc.; (see § 278) as,--

sit fūr, sit sacrilegus, at est bonus imperātor, _granted that he is a thief and a robber, yet he is a good commander_;

haec sint falsa, _granted that this is false_;

nē sit summum malum dolor, malum certē est, _granted that pain is not the greatest evil, yet it is certainly an evil_.

Adversative Clauses with _Quamvīs_, _Quamquam_, etc.

309. Clauses introduced by quamvīs, quamquam, etsī, tametsī, cum, _although_, while often classed as 'Concessive,' are yet essentially different from genuine Concessive clauses. As a rule, they do not _grant_ or _concede_ anything, but rather state that something is true _in spite of something else_. They accordingly emphasize the adversative idea, and are properly Subordinate Adversative Clauses. The different particles used to introduce these clauses have different meanings and take different constructions, as follows:--

1. Quamvīs, _however much_, _although_, does not introduce a statement of fact, but represents an act merely as conceived. It is followed by the Subjunctive, usually of the present tense; as,--

hominēs quamvīs in turbidīs rēbus sint, tamen interdum animīs relaxantur, _in however stirring events men may engage, yet at times they relax their energies;_

nōn est potestās opitulandī reī pūblicae quamvīs ea premātur perīculīs, _there is no opportunity to succor the state, though it be beset by dangers._

2. Quamquam, etsī, tametsī, _although_, introduce a statement of fact, and are followed by the Indicative (of any tense); as,--

quamquam omnis virtūs nōs allicit, tamen jūstitia id maximē efficit, _although all virtue attracts us, yet justice does so especially;_

Caesar, etsī nōndum cōnsilium hostium cognōverat, tamen id quod accidit suspicābātur, _Caesar, though he did not yet know the plans of the enemy, yet was suspecting what actually occurred_.

a. Etsī, _although_, must be distinguished from etsī, _even if_. The latter is a conditional particle and takes any of the constructions admissible for sī. (See §§ 302-304.)