[1854.] quod often has a correlative in the main sentence, such as eō, ideō, idcircō, proptereā. In Sallust, eā grātiā. In Plautus, causal quod is very rare compared to causal quia.
[1855.] An untenable reason is introduced in Plautus by nōn eō quia, in Terence by nōn eō quō; in Cicero very rarely by neque or non eō quō, usually by nōn quod or nōn quō; by nōn quia rarely in classical Latin, but commonly from Livy on. The valid reason follows, with sed quod, sed quia, or with sed and a fresh main sentence.
The mood is usually subjunctive ([1725]): as, pugilēs ingemīscunt, nōn quod doleant, sed quia prōfundendā vōce omne corpus intenditur, TD. 2, 56, boxers grunt and groan, not because they feel pain, but because by explosion of voice the whole system gets braced up. Sometimes, but very rarely in classical prose, the indicative. Correlatives, such as idcircō, ideō, &c., are not uncommon. Reversed constructions occur, with magis followed by quam, as: magis quod, quō, or quia, followed by quam quō, quod, or quia. The negative not that . . . not, is expressed by nōn quod nōn, nōn quō nōn, or nōn quīn.
[quia.]
[1856.] quia, a neuter accusative plural of the relative stem ([701]) is used in both a declarative and a causal sense, like quod ([1838]). It is, however, more prevalent in Plautus, less so from Terence on.
[1857.] For the uses of declarative quia, see under 1848, 1850, 1851.
[1858.] Causal quia, with or without a correlative, such as ideō, eō, proptereā, &c., is common in old Latin ([1854]) and poetry, unusual in prose (once in Caesar) before Tacitus. For nōn quia, &c., see [1855].
[quom or cum.]
[1859.] quom or cum ([157], [711]), used as a relative conjunctive particle ([1794]), has a temporal meaning, when, which readily passes over to an explanatory or causal meaning, in that, since or although. In both meanings it introduces the indicative in old Latin. In classical Latin, temporal cum in certain connections, and causal cum regularly, introduces the subjunctive. The subjunctive is also used with cum for special reasons, as in the indefinite second person ([1731]), by attraction ([1728]), and commonly by late writers to express repeated past action ([1730]). cum, when, is often used as a synonym of sī, if, and may then introduce any form of a conditional protasis ([2016], [2110]).