Letter XII is addressed to Æonius, bishop of Arles (roughly 485–502), and was written on August 23, 494 — just eighteen days after Letter XI to the bishops of Dardania and Illyricum. The two letters together show Gelasius in his active primatial correspondence during the summer of 494, attending at once to the Acacian Schism in the East and to the maintenance of communion with the Gallic churches in the West. The occasion of the letter is largely practical — two Gallic envoys, returning from Italy after a supply mission for a religious community, are available to carry a letter — but Gelasius uses the occasion to make a striking statement of Roman primacy that grounds everything that follows.

The heart of the letter for the primacy question is the second paragraph. Gelasius writes: B. Petri apostoli gubernatio principalis universo gregi debet in orbe terrarum — “the principal governance of the Blessed Apostle Peter owes [care] to the universal flock throughout the world.” Three elements of this formula deserve close attention. The first is the adjective principalis — “principal,” “governing,” “originating” — the same term Leo I had used (in the adverbial form principaliter) in Letter X to characterize Peter’s position among the apostles. For Leo, Peter was the one in whom the mystery of the universal office was principally placed, from whom as from a head Christ’s gifts flow to the whole body. Gelasius inherits the vocabulary and applies it directly to the governance: Peter’s governance is principal — the one from which all else derives. The second element is the verb debet — “owes.” Peter’s governance owes care to the universal flock. This is not a governance that exists for Peter’s benefit, or for Rome’s aggrandizement, but a governance under obligation to those it governs. The third element is the scope: universo gregi… in orbe terrarum — “to the universal flock throughout the world.” The care owed is not restricted to a particular region, rite, or administrative jurisdiction; it is owed to every Christian flock everywhere.

Equally important is the grounding clause Christo Domino delegante — “with Christ the Lord delegating [it].” Gelasius names the source of the governance explicitly. Peter holds this care because Christ delegated it to him. The governance is not a standing won by custom, by conciliar concession, or by imperial grant; it is a delegation from Christ. The reader who is tracing the development of the primacy vocabulary across the fifth century should note that Gelasius here combines in a single sentence what had been various threads in earlier papal writing: Leo’s language of Peter as the head, the universal scope of the care owed, and the direct delegation from Christ as the grounding of the whole claim. The result is one of the most compressed and juridically explicit statements of Roman primacy in the fifth-century papal corpus, and it appears not in a controversial letter addressing a crisis but in a brief pastoral greeting to a Gallic metropolitan.

The ecclesiological logic of the paragraph should also be observed. Gelasius does not merely assert Peter’s governance; he derives a consequence from it. Because the governance owes care to the universal flock, the Apostolic See “embraces all the Churches and their rulers with so great an affection of piety.” The care owed generates the embrace. The primacy is not a standing to be displayed but a solicitude to be exercised, and the exercise of the solicitude takes the form of affectionate concern for every local church and its bishop. This is the same structural pattern visible throughout the Gelasian corpus and, before it, the Leonine: the theological claim about Peter generates an ecclesiological obligation for Rome, and that obligation is discharged through active pastoral correspondence.

The relationship to Arles deserves a brief historical note. Arles had been a site of significant primacy-related tensions in the fifth century. Under Hilary of Arles, the see had overextended its claims — usurping ordinations in other provinces and conducting synods beyond its jurisdiction — and Leo I had responded by stripping Hilary of metropolitan authority over the province of Vienne (Letter X of Leo, 445). The see’s metropolitan standing was later restored under Leo’s successors, and by Gelasius’s time Arles was a respected and cooperative metropolitan see in communion with Rome. Letter XII shows this normal, restored relationship: Gelasius writes to Arles not to discipline but to greet, and he entrusts Æonius with the further task of conveying greetings to the other Gallic bishops. The implicit structural premise is the same one established under Leo — Arles is a metropolitan through which communication with the Gallic churches is normally conducted — now operating in its proper, restored mode.

The concluding request of the letter is itself a primacy datum, though a quiet one. Gelasius asks Æonius to communicate Rome’s affection to the Gallic bishops generally, through whatever further messengers he should choose. This is the common pattern of Roman correspondence: rather than writing individually to every bishop of a province, the pope writes to the metropolitan, who then circulates or communicates the contents. The reader who is familiar with Leo’s letters to Anastasius of Thessalonica (Letters V, VI of Leo) — where the pope communicates with the bishops of Illyricum through the metropolitan — will recognize the same pattern here applied to Gaul. The practice is both administratively practical and ecclesiologically meaningful: the ranking bishop of a province is the proper channel for communication with his suffragans, and the pope, acting as universal pastor, addresses the province through its proper head. The Catholic profession, as Gelasius says at the close of the letter, remains “always and everywhere joined” — and the practice of corresponding through metropolitans is one of the concrete ways this universal joining is maintained.