Letter XVI, dated July 15, 482, is the first surviving letter of the Simplicius corpus since Letter XV in 479 — a gap of approximately three years during which no correspondence has been preserved. The letter is short but carries a significance disproportionate to its length, because of what it confirms, what it reveals, and when it was written.

What it confirms is the election of Calendio as bishop of Antioch, succeeding Stephen the Younger who had died in the third year of his episcopate. The confirmation is expressed in the formal language of Roman reception: Simplicius “embraces the priesthood of Calendio in the bosom of the Apostolic See” and “counts the bishop of so great a city in Our fellowship, in the union of the college.” The language is Rome’s standard formula for receiving a new bishop of a major see into communion: the Apostolic See embraces, the bishop is received. The act is not a courtesy acknowledgment but a jurisdictional confirmation — the same kind of act Simplicius had performed when receiving Timothy Salofaciolus’s restoration in the earlier letters. Without Rome’s embrace, the bishop’s standing in the universal communion is incomplete.

What it reveals is that Acacius has stopped keeping Rome informed. The rebuke is pointed: “We are surprised that We have learned nothing about the state of the Antiochene Church from your instruction.” In Letter XIII (October 478), Simplicius had explicitly charged Acacius with a reporting obligation: “whatever you obtain from the most religious empire, let the care of Your Charity bring it to my notice, and make Us partners in the actions pertaining to the preservation of evangelical doctrine.” By July 482, Acacius has failed to fulfill that obligation. Simplicius has had to learn about the crisis at Antioch from other sources — from Calendio’s own synod and from the envoy Anastasius — rather than from the patriarch of Constantinople. This is the first concrete sign in the Simplicius correspondence that the cooperative relationship between Rome and Constantinople has broken down. Acacius is no longer functioning as Rome’s reliable intermediary in the East.

When it was written is what gives the letter its historical weight. July 15, 482 falls in the last months before the Henoticon — the Emperor Zeno’s formula of faith that sought to reconcile the Monophysites by effectively sidelining the Council of Chalcedon. The Henoticon would be issued later in 482, and its acceptance by Acacius would be the proximate cause of his excommunication by Felix III in 484 and the opening of the Acacian Schism. Simplicius’s closing warning — that what was achieved under tyrants must not be overturned under Zeno’s reign — reads in retrospect as a prophecy of precisely what was about to happen. The settlement of 476–478 that the entire preceding correspondence had worked to secure — the restoration of Timothy Salofaciolus, the expulsion of heretical bishops, the preservation of the Nicene order — would be undone by the emperor’s own hand before the year was out. Acacius’s silence, which Simplicius here rebukes, was not mere negligence; it was the silence of a patriarch who was already moving in a direction he knew Rome would not approve.

The death of Timothy Salofaciolus, mentioned in the letter as the occasion the wicked are exploiting, marks the end of the Alexandrian chapter that had dominated the Simplicius correspondence since Letter IV. Timothy’s restoration had been the signal achievement of the 477–478 cooperation between Rome, Constantinople, and the imperial court. His death removed the Catholic anchor at Alexandria and created the conditions for Peter Mongus’s return — the very outcome Simplicius had spent four letters (X through XIII) trying to prevent by demanding Peter’s exile. Everything Simplicius warned against has now come to pass: Peter was not exiled, Timothy has died, and the settlement is collapsing. The reader who has followed the corpus from Letter IV to this point will recognize the trajectory: a pope whose directives were clear, consistent, and repeatedly issued, working through an intermediary who initially cooperated but has now gone silent, addressing an emperor who initially complied but is about to reverse course. The Acacian Schism was not a sudden break but the culmination of a pattern visible across the entire Simplicius correspondence.