[1872.] With cum, when, the imperfect or pluperfect subjunctive is used to describe the circumstances under which the action of the main clause took place: as,
cum rēx Pyrrhus populō Rōmānō bellum intulisset cumque dē imperiō certāmen esset cum rēge potentī, perfuga ab eō vēnit in castra Fabriciī, Off. 3, 86, king Pyrrhus having made war on the Roman nation, and there being a struggle for sovereignty with a powerful king, a deserter from him came into Fabricius’s camp. eōdem tempore Attalus rēx moritur alterō et septuāgēsimō annō, cum quattuor et quadrāgintā annōs rēgnāsset, L. 33, 21, 1, the same year Attalus the king dies, in his seventy-second year, having reigned forty-four years. hīc pāgus, cum domō exīsset patrum nostrōrum memoriā, L. Cassium cōnsulem interfēcerat, 1, 12, 5, this canton, sallying out from home in our fathers’ recollection, had put Cassius, the consul, to death. nam cum inambulārem in xystō, M. ad mē Brūtus vēnerat, Br. 10, for as I was pacing up and down my portico, Brutus had come to see me. Antigonus in proeliō, cum adversus Seleucum et Lȳsimachum dīmicāret, occīsus est, N. 21, 3, 2, Antigonus was killed in battle fighting against Seleucus and Lysimachus. haec cum Crassus dīxisset, silentium est cōnsecūtum, DO. 1, 160, a deep silence ensued after Crassus had finished speaking. cum annōs iam complūrīs societās esset, moritur in Galliā Quīnctius, cum adesset Naevius, Quinct. 14, the partnership having lasted several years, Quinctius died in Gaul, Naevius being there at the time.
In this use, as the examples show, cum with the subjunctive is often equivalent to a participle or an ablative absolute. The use is not found in Plautus ([1861]). Ennius and Terence have possibly each an instance (disputed) of it, but it was certainly rare until the classical period, when it became one of the commonest of constructions. It must not be confounded with the special uses of the subjunctive mentioned in 1859.
[1873.] The difference in meaning between cum with the indicative and cum with the subjunctive may be illustrated by the following examples:
Gallō nārrāvī, cum proximē Rōmae fuī, quid audīssem, Att. 13, 49, 2, I told Gallus, when I was last in Rome, what I had heard ([1866]), a. d. III kal. Maiās cum essem in Cūmānō, accēpī tuās litterās, Fam. 4, 2, 1, I received your letter on the twenty-eighth of April, being in my villa at Cumae ([1872]). cum vāricēs secābantur C. Mariō, dolēbat, TD. 2, 35, while Marius was having his varicose veins lanced, he was in pain ([1864]). C. Marius, cum secārētur, ut suprā dīxī, vetuit sē adligārī, TD. 2, 53, Marius being under the surgeon’s knife, as above mentioned, refused to be bound ([1872]). num P. Decius, cum sē dēvovēret et in mediam aciem inruēbat, aliquid dē voluptātibus suīs cōgitābat? Fin. 2, 61, did Decius, offering himself up, and while he was dashing straight into the host, have any thought of pleasures of his own? ([1872], [1864]).
(B.) Explanatory and Causal cum.
[1874.] The indicative is often used with explanatory cum when the action of the protasis is coincident with that of the apodosis ([1733]).
In this use cum passes from the meaning of when to that, in that, or in or by with a verbal in -ing: as, hoc verbum quom illī quoidam dīcō, praemōstrō tibī̆, Pl. Tri. 342, in laying down this lesson for your unknown friend I’m warning you. cum quiēscunt, probant, C. 1, 21, their inaction is approval. Denoting the means: as, tūte tibi prōdes plūrumum, quom servitūtem ita fers ut ferrī decet, Pl. Cap. 371, you do yourself most good by bearing slavery as it should be borne. For similar uses of quod, quia, and quī, see [1850].
[1875.] Explanatory cum is also used with verbs of emotion; likewise with grātulor and grātiās agō: as, quom tu ’s līber, gaudeō, Pl. Men. 1148, that you are free, I’m glad. grātulor tibī̆, cum tantum valēs apud Dolābellam, Fam. 9, 14, 3, I give you joy that you stand so well with Dolabella. tibī̆ maximās grātiās agō, cum tantum litterae meae potuērunt, Fam. 13, 24, 2, I thank you most heartily in that my letter had such influence. For similar uses of quod and quia, see [1851], [1852].