[1379.] The instrumental ablative is used with the five deponents fruor, fungor, potior, ūtor, vēscor, and several of their compounds, and with ūsus est and opus est: as,
pāce numquam fruēmur, Ph. 7, 19, we never shall enjoy ourselves with peace, i.e. we never shall enjoy peace. fungar vice cōtis, H. AP. 304, I’ll play the whetstone’s part. castrīs nostrī potītī sunt, 1, 26, 4, our people made themselves masters of the camp. vestrā operā ūtar, L. 3, 46, 8, I will avail myself of your services. carne vēscor, TD. 5, 90, I live on meat. opust chlamyde, Pl. Ps. 734, there is a job with a cloak, i.e. we need a cloak.
[1380.] Instead of the instrumental ablative, some of the above verbs take the accusative occasionally in old and post-Augustan Latin: thus, in Plautus, Terence, Cato, always abūtor, also fungor, except once in Terence; fruor in Cato and Terence, and perfungor in Lucretius, once each; potior twice in Plautus and three times in Terence, often also the genitive ([1292]). The gerundive of these verbs is commonly used personally in the passive, as if the verbs were regularly used transitively ([2244]).
[1381.] ūtor often has a second predicative ablative: as, administrīs druidibus ūtuntur, 6, 16, 2, they use the druids as assistants. facilī mē ūtētur patre, T. Hau. 217, an easy-going father he will find in me.
[1382.] ūsus est and opus est sometimes take a neuter participle, especially in old Latin: as, vīsō opust cautōst opus, Pl. Cap. 225, there’s need of sight, there’s need of care. Sometimes the ablative with a predicate participle: as, celeriter mī eō homine conventōst opus, Pl. Cur. 302, I needs must see that man at once.
[1383.] With opus est, the thing wanted is often made the subject nominative or subject accusative, with opus in the predicate: as, dux nōbīs et auctor opus est, Fam. 2, 6, 4, we need a leader and adviser. Usually so when the thing needed is a neuter adjective or neuter pronoun: as, multa sibī̆ opus esse, V. 1, 126, that he needed much. A genitive dependent on opus is found once or twice in late Latin ([1227]).
[1384.] ūsus est is employed chiefly in comedy, but also once or twice in Cicero, Lucretius, Vergil, and Livy. Once with the accusative: ūsust hominem astūtum, Pl. Ps. 385, there’s need of a sharp man.
[The Ablative of Specification.]
[1385.] The instrumental ablative is used to denote that in respect of which an assertion or a term is to be taken: as,