All these forms are subject to the general rules of the Conditional Statement §§ 234 sqq.
§ 417. Mixture of Types of Conditional Statement.—The general rule for the formation of the Conditional Statement, that the Protasis and Apodosis must not consist of forms inconsistent with each other, is subject to some exceptions.
(a) There being no Indicative of the Indefinite Second Person (§355) the Subjunctive is used instead: standum est in lĕctō sī quid dē summō pĕtās one must stand on the sofa if one wants anything from the top.
If any other person is used, the Ind. is necessary. Hence: sī quĭd pĕtĭmŭs or sī quĭd pĕtĭtŭr.
(b) The Indicative is used regularly in phrases like longum est it would be long.
| Longum est'sī omnīă nārrem | It would be a long affair if I told everything. |
| Mĕ1ĭŭs ĕrăt'sī dīmĭcāssĕt | It would have been better if he had fought. |
(c) The Subjunctive (especially in the Secondary Tenses) is occasionally replaced by an expression in the Indicative, which means nearly the same as the Subjunctive. Thus in sīiŭssĕs, pārŭissem if you had ordered me, I should have obeyed; instead of saying I should have obeyed, which implies I did not obey, we might say I ought to have obeyed, I was going to obey, or the like.
| Sī sīgnum dătum essĕt, If a signal had been given, |
pūgnārĕ debebant it was their duty to fight. | |
| pūgnārĕ pŏtĕrant they were able to fight. | ||
| pūgnandum ĕrăt they were obliged to fight. | ||
| pūgnātūrī ĕrant they were on the eve of fighting. | ||
| pūgnābant they were for fighting (§ 178). |
