est, fēlīx est does not mean either that he IS good or that he IS happy, but only that he is happy IF he is good.
§ 238. Any Tense of the Indicative may be used in either Protasis or Apodosis if it gives an intelligible sense:
si iŭbēs, ībō If you are ordering me (now), I will go;
si iŭbēbīs, ībō If you order me (in the future), I will go;
si Athēnīs ĕrăt, Cŏrinthum vĕnĭĕt If he was at Athens, he will come to Corinth;
si peccāvī, paenĭtĕt If I have done wrong, I am sorry.
§ 239. Subjunctive in Conditional Statements.—If we use the Subjunctive in a Conditional Statement, we treat the events as if they were mere imaginations, and we imply that they do not occur.
Such imaginary suppositions are expressed by a different set of tenses according as they relate (B) to the Future or (C) to the Present and Past.
§ 240. (B)—Primary Tenses of the Subjunctive.—These express imaginary suppositions relating to the Future. In these we do not expect the event to occur, though, of course, as it is in the future, it may occur notwithstanding.
sī interrŏgēs, respondĕam If you were to ask me, I should answer;
sī peccāvĕrīs, paenĭtĕăt If you should do wrong (should have done wrong), you zvould be sorry.
§ 241. (C)—Secondary Tenses of the Subjunctive.—These express imaginary suppositions relating to (a) the Present or (b) the Past. Such suppositions are known to be contrary to the fact, and the events which they suppose are known not to be occurring or not to have occurred.
Conditional statements of this kind always implicitly deny something. Thus in sī hīc essēs, ălĭtĕr sentīrēs If you were here, you would think differently, we implicitly deny that you are here. We imply hīc nōn ĕs you are not here.
§ 242. (a) Imaginary Suppositions relating to the Present Time.—Here the Imperfect Subjunctive corresponds to a Present Indicative of the Implied Statement, and the Pluperfect Subjunctive to a Perfect Indicative.
