Atrox visum est id facinus patribus plebique. This hideous crime was seen by the patricians and plebs.
Why does Orberg use plebi instead of plebe? Assuming it isn’t a typo, what kind of dative is plebi?
Passive videri means “to seem” and takes a dative complement–indirect object.
See Lewis and Short video, b7:
7 Pass., to be looked upon or regarded in any manner, i. e. to seem, appear to be or do any thing: . . . > With dat. of pers.> : cetera, quae > quibusdam > admirabilia videntur, etc., Cic. Lael. 23, 86: digna > mihi > res cum omnium cognitione tum nostrā familiaritate visa est, id. ib. 1, 4: idonea > mihi > Laelii persona visa est, quae, etc., id. ib.: a naturā > mihi > videtur potius quam ab indigentiā orta amicitia, id. ib. 8, 27: quae > Aristoni et Pyrrhoni > omnino visa sunt pro nihilo, id. Fin. 2, 13, 43: quod idem > Scipioni > videbatur, id. ib. 4, 14.—Parenthet. (cf. c. infra): quam nostris libris satis diligenter, ut > tibi > quidem videmur, expressimus, Cic. Att. 8, 11, 1: Philargyrus omnia de te, ut > mihi > quidem visus est, narravit, id. Fam. 4, 13, 3.—
Atrox here is a predicate adjective.
“This crime seemed horrible to the Senate and the People.”