Non prævalebunt adversus/adversum eam

Question

After several years, a Bible verse I thought I knew well just blew my mind. (Well, they sometimes do, but not in the grammatical sense.)

Namely, Mt 16:18 says,

And so I say to you, you are Peter, and upon this rock I will build my church,* and the gates of the netherworld shall not prevail against it.

Clementine Vulgate (as per the Clementine Vulgate project in Sourceforge) says,

Et ego dico tibi, quia tu es Petrus, et super hanc petram ædificabo Ecclesiam meam, et portæ inferi non prævalebunt adversus eam.

Meanwhile, Nova Vulgata, (as per the Holy See) says,

Et ego dico tibi: Tu es Petrus, et super hanc petram aedificabo Ecclesiam meam; et portae inferi non praevalebunt adversum eam.

FWIW, the original Greek says,

κἀγὼ δέ σοι λέγω, ὅτι σὺ εἶ Πέτρος, καὶ ἐπὶ ταύτῃ τῇ πέτρᾳ οἰκοδομήσω μου τὴν ἐκκλησίαν, καὶ πύλαι ᾅδου οὐ κατισχύσουσιν αὐτῆς.

Here, κατισχύσουσιν seems to have the against part implicit in the meaning of the verb.

As I understand, adversus is an adjective, while adversum may also be an adverb. While the latter seems more reasonable (prevail against), I guess the former is also idiomatic. (Is it, even if non-Clasically?).

Is the New Vulgate correcting something that the Vulgate had less correctly conveyed?

Answer 1

No, both adversum and adversus are adverbs/preposition here, not an adjective. It's actually listed under adversus in Lewis and Short:

adversus or adversum (archaic advor- ) (like rursus and rursum, prorsus and prorsum, quorsus and quorsum), adv. and prep., denoting.
I. direction to or toward an object (syn.: contra, in with acc., ad, erga).
A. Adv.: opposite to, against, to, or toward a thing, in a friendly or hostile

See below in the passage for a direct comparison with contra:

2. In a hostile sense, against (the most usual class. signif. of this word): “Contra et adversus ita differunt, quod contra, ad locum, ut: contra basilicam; adversus, ad animi motum, ut: adversus illum facio; interdum autem promiscue accipitur,”

With κατισχύσουσιν, the prefix κατα- is what's giving it the adversative meaning. See its entry in the LSJ.

5. in hostile sense, against, A.Ch.221, S.Aj.304, etc.; “κ. πάντων φύεσθαι” D.18.19; esp. of judges giving sentence against a person, A.Th.198, S.Aj.449, etc.; “ψεύδεσθαι κατά τινος” Lys.22.7; “λέγειν κατά τινος κακά” S.Ph.65, cf. X.HG1.5.2, etc.; of speeches, [λόγος] κ. Μειδίου, etc. (opp. πρὸς Λεπτίνην, in reply to L.); “δῶρα εἰληφέναι κατά τινος” Din.3.6, cf. 18.

Answer 2

"Adversus" is often used as an adverb or preposition. The "-us" ending is unusual for that part of speech, but it follows use of "versus" as an adverb. (L&S's entry on verto says there are no clear ancient examples of "versus" by itself being used as a preposition, but it was often used as an adverb with a preposition, e.g. (taking examples from that entry) "ad Alpes versus" or "ad Cordubam versus", and I guess the use of "adversus" is related to that use of "ad ... versus". It's not clear to me that "versus" in that context is really an adverb rather than a postposition that selects a prepositional phrase as its complement, but anyway, the point is that it's not exclusively an adjective.)

"Adversus eam" seems to use the more common variant compared to "adversum eam". I'm not sure why Clementine Vulgate uses one and Nova Vulgata the other.

Allen and Greenough seems to say that there's a difference in meaning, but doesn't really explain it (a gloss with a single English preposition certainly isn't adequate to describe the usage of a Latin one):

adversus against
adversum towards

Nonetheless, I don't think they actually mean different things.