Letter IX, dated March 13, 478, is Simplicius’s direct response to the letter Acacius had sent reporting the death of Timothy Aelurus, the flight of Peter Mongus, and the restoration of the Catholic Timothy Salofaciolus to Alexandria. The letter is congratulatory in form: Simplicius rejoices with Acacius, praises the emperor Zeno, and welcomes the restored Timothy as “Our brother and fellow bishop.” But the editorial weight of the letter falls on its closing sentences, where Simplicius raises a concern that would govern the next forty years of Eastern–Western ecclesiastical history.

The concern is the question of the diptychs. Timothy Salofaciolus, although a Catholic, had at some earlier point during his troubled tenure at Alexandria been pressured by the Monophysite party into allowing the name of Dioscorus — the patriarch condemned and deposed at Chalcedon — to remain in the diptychs of the Alexandrian altars. The diptychs were the lists of names that the bishop commemorated during the Eucharistic liturgy, and inclusion in them was the formal mark of being in communion with the celebrating church. To commemorate Dioscorus at the altar was to treat him as still in communion; to remove his name was to confirm his deposition. Timothy’s earlier compromise — extracted from him under pressure, as Simplicius is careful to note — had been a concession to local Monophysite feeling to preserve peace in Alexandria. Simplicius is here, even as he congratulates Timothy’s restoration, gently but firmly recalling the lapse and asking that Timothy be “found blameless” going forward. The implication is unmistakable: this kind of compromise must not be repeated.

The reader who knows the trajectory of the Acacian Schism will recognize what Simplicius is doing. The diptychs question would become the central question of the schism. Within four years, Acacius himself would be the principal architect of Zeno’s Henoticon (482), which sought reconciliation with the Monophysites on terms that included the commemoration of Peter Mongus — the very Peter whose flight Acacius had reported in the previous letter — in the Constantinopolitan diptychs. Within six years of this letter, Felix III would excommunicate Acacius, and the inclusion of Peter Mongus in the diptychs would be one of the principal grounds. Within forty-one years, the Formula of Hormisdas (519) would resolve the schism by specifically requiring the removal of certain names — including Acacius’s own — from the diptychs of every church seeking restored communion with Rome. Simplicius’s letter to Acacius in 478 is the first explicit Roman intervention in what would become this entire trajectory. The letter does not contain the word “Henoticon” or any premonition of what is coming. But the principle it articulates — that compromise on the diptychs is a failure of episcopal constancy — is exactly the principle that would govern Rome’s judgment of Acacius and his successors for the next four decades.

Equally important is the structural assumption of the letter’s closing request. Simplicius asks Acacius to admonish Timothy — commonente dilectione tua. This is a delegation of pastoral oversight: Acacius is being asked to function as the local agent for Roman concern about Alexandrian conduct, monitoring Timothy and admonishing him as needed. The reader should note what this presupposes about how Simplicius understood the relationship between Rome, Constantinople, and Alexandria. Constantinople is the natural conduit for Roman pastoral concern when distance prevents direct engagement; the patriarch of Constantinople is treated as the figure through whom Roman oversight of Alexandria can be conducted in practice. The same pattern Leo had used when delegating oversight of the Eastern churches to Anatolius and Julian of Cos in his own correspondence here governs Simplicius’s relationship with Acacius. The Roman bishop is not asking Constantinople for help as one bishop asks another for a favor; the Roman bishop is delegating a task that Constantinople is expected to perform on Rome’s behalf.

The praise of Zeno that occupies the middle of the letter deserves brief notice. Simplicius compliments the emperor not merely for his Catholic devotion but for the promptness of it — Zeno acts so quickly, the figure runs, that his devotion outpaces even the priests’ messengers, doing what they would ask before they can ask it. The reader should weigh this in the context of what was actually true at the moment: Zeno had repudiated the Encyclical of Basiliscus, restored the orthodox bishops, and was cooperating fully with the Catholic party. The compliment was earned. Within four years, however, the same Zeno would issue the Henoticon and undo much of what Simplicius is here praising him for. Letter IX, like the previous letter from Acacius, captures the moment of greatest cooperation between Rome, Constantinople, and the imperial throne — and it is the last letter of the Simplicius correspondence in which that cooperation appears unqualified. From this point forward in the Simplicius corpus, the relationship would begin to bear the strain of the diptychs question and the slow drift toward the Henoticon.