Letter XII — misnumbered as XIII in PL, which prints XIII on both this letter and the next. The correct sequential number is XII; the following letter is XIII. This is the third of Simplicius’s letters to Zeno requesting the exile of Peter Mongus from Alexandria. The first request was in Letter X; the second was channeled through Acacius in Letter XI; this third is again addressed directly to the emperor. The repetition is itself significant: by October 478, Simplicius has been asking for Peter’s exile for months, and the fact that he is still asking means the emperor has not yet acted. The pattern of request, delay, and re-request would characterize the remainder of the Simplicius pontificate and would contribute to the conditions in which Peter Mongus was eventually able to return — not as a fugitive but as the imperially-recognized patriarch under the Henoticon (482).

The letter is short and its primacy content is relatively light compared to the major letters of the corpus. Its most significant detail is the canonical judgment on Peter Mongus’s standing: he could not maintain legitimate rank even as a deacon. This is not rhetorical abuse but a canonical finding. Peter’s diaconal ordination was irregular or had been invalidated by his association with Timothy Aelurus and the Monophysite party; his claim to the episcopate was therefore built on a foundation that was already canonically void. Simplicius is giving Zeno a canonical reason for the exile that goes beyond the political and theological arguments of the earlier letters: this man has no legitimate standing at any level of the clergy, and his presence in Alexandria is a standing violation of canonical order.

The praise of Zeno as both “witness and judge” of the Alexandrian struggles deserves notice. Simplicius is not merely flattering the emperor; he is binding him to the consequences of his own acts. A judge who renders a verdict is obligated to enforce it. By reminding Zeno that he has already judged the Alexandrian case — restoring the Catholic Timothy, expelling the heretical invader — Simplicius is saying that the exile of Peter Mongus is not a new request but the logical completion of a judgment Zeno has already made. The failure to enforce one’s own judgment is not clemency; it is inconsistency.

The closing sentence — that God preserves the Roman Empire through Zeno’s clemency, to the joy of the whole world and the exultation of the universal Church — echoes the imperial theology of Letter VIII (the Davidic comparison, the continuity argument). The empire’s preservation is attributed to divine protection, and that divine protection is linked to the emperor’s fidelity. The implicit converse remains: an emperor who ceases to protect the faith ceases to merit the protection. This is the same theological warning Simplicius issued in Letter VIII, now delivered more briefly but with the same underlying logic.