Letter VI is the formal excommunication and deposition of Acacius of Constantinople — the juridical act that opened the Acacian Schism. Issued by Roman Council II on July 28, 484, and subscribed by Felix and sixty-seven other bishops, the sentence was delivered to Constantinople and, according to tradition preserved in Liberatus and Nicephorus, pinned to Acacius’s pallium by a monk of the Akoimetai while the patriarch was proceeding to celebrate the liturgy. The schism that followed would last thirty-five years, ending only with the Formula of Hormisdas in 519 — a document that would make explicit the Eastern acknowledgment of Roman primacy that Felix’s sentence had presupposed. For the site’s readers, Letter VI is therefore one of the most consequential primary-source documents in the entire pre-medieval Roman correspondence: the juridical act by which Rome exercised the authority it claimed, and the Eastern rejection and eventual acceptance of which mark the practical boundaries of that authority in the fifth and sixth centuries.

The letter should be read as the culmination of a process that began under Simplicius in 477. Simplicius’s letters to Acacius (V, VI, VII, IX, X, XI, XII, XIII) had catalogued the Eastern crisis step by step: the death of Timothy Aelurus, the brief installation of Peter Mongus, Zeno’s restoration of Timothy Salofaciolus, the death of Timothy Salofaciolus in 482, the canonical election of John Talaia, and Zeno and Acacius’s displacement of Talaia in favor of Peter Mongus under the Henoticon. At each stage Simplicius had admonished Acacius and had received his nominal compliance — Acacius had even petitioned Rome to condemn Peter Mongus. The reader should notice what Felix does with this history in Chapter I: the charge is not that Acacius has newly refused Rome but that he has reversed his own prior recognition of Rome’s condemning authority. The continuity principle is preserved: Felix is not innovating Roman authority over Constantinople, he is enforcing what Acacius himself had acknowledged, now against Acacius himself.

Three distinct primacy formulae operate in the letter, each doing a different kind of work. The first — ab apostolica institisti sede damnari, “you petitioned the Apostolic See to condemn” — establishes the past recognition. The second — in apostolica sede secundum canones respondere, “to respond in the Apostolic See according to the canons” — establishes the procedural present: the Apostolic See holds juridical authority over the universal Church, and canonical procedure is the governing standard for how that authority is exercised. John Talaia’s libellus is the standard form in which such jurisdiction is invoked, and Acacius’s refusal to answer it is an admission under the principles that governed Roman juridical practice generally. The third — in læsionem beati Petri apostoli, a cujus sede profecti fuerant, “to the injury of the blessed Apostle Peter, from whose see they had set out” — establishes the theological identification: the legates are not private envoys of the pope but extensions of Peter’s own authority. To corrupt them is to assault the Apostle himself. The three formulae together constitute the letter’s primacy architecture: past recognition, present jurisdiction, and theological identification of Peter with his see.

The sentence itself, in Chapter V, is carefully framed. Two warrants operate in conjunction: sancti Spiritus judicio (by the judgment of the Holy Spirit) and apostolica auctoritate per nos (by Apostolic Authority through Us). The first names the theological ground, the second names the juridical instrument. They are not alternatives but a single action: the Holy Spirit judges through the Apostolic Authority the Roman bishop exercises. This is what makes the anathema perpetual. A juridical sentence imposed by human authority could be lifted by human authority; but a sentence that is simultaneously the Holy Spirit’s own judgment can only be resolved by a return to the communion from which the condemned has separated himself. The phrase nec jam unquam anathematis vinculis exuendus — “never to be loosed from the bonds of anathema” — is not a rhetorical flourish but a theological consequence of how the sentence is grounded. What the Spirit has judged, mere ecclesiastical diplomacy cannot untie.

The procedural regularity of the act deserves particular attention. Felix is not acting by raw papal authority but by authority exercised according to form: a libellus was filed, the accused was summoned to appear, canonical procedure was invoked, a Roman council was convened, sixty-seven bishops concurred, the sentence was subscribed and delivered through the defensor of the Church. The site’s readers — Orthodox and Protestant as well as Catholic — will find here not a capricious Roman exercise of power but a canonical act carried out with every procedural safeguard. The same architecture is visible in Leo’s Letter X against Hilary of Arles — a libellus, a canonical summons, a conciliar act, a subscribed sentence — applied now not to a Gallic suffragan but to the patriarchate of Constantinople. What changes between the Gallic and Constantinopolitan cases is the political weight of the respondent, not the Roman procedure. This regularity should not be confused with its supposed source. The canons of Sardica (343) are sometimes invoked to argue that Rome’s role in receiving cases like this derives from a conciliar grant — that Rome operates as an appellate court authorized by Sardica, not as the holder of a primacy that predates any council. Felix’s letter does not rest on Sardica or on any conciliar warrant. Its grounds, as stated in the text itself, are Peter’s keys from the Savior, the Apostolic See as Peter’s own see in which he lives and judges, and the Holy Spirit’s judgment exercised through Apostolic Authority. The canonical procedure Rome follows is how Rome’s primacy is responsibly exercised, not the source of it. Rome does not judge because Sardica authorized judging; Sardica’s canons on appeals presupposed an authority Rome already held.