The Cost of Peace

The Formula of Reunion of 433 ended the schism between Alexandria and Antioch, but it did so by alienating the zealots of both parties. To Cyril’s own hardliners — the strict Cyrillians, the zealous monks of Egypt, and the future Miaphysite leaders — the acceptance of “two natures” looked like a sell-out, a surrender of the Twelve Anathemas; Cyril spent the rest of his life writing letters to reassure them. To the intransigent Antiochenes who would not abandon Nestorius, John of Antioch’s signature was an apostasy, and they broke communion with him rather than accept the settlement; their remnant fed the future Church of the East. This file traces the cost of peace on both flanks, Cyril’s defenses and his theoria distinction, his own hardening after 433, and the lasting ambiguity of a settlement held together largely by one man.

Tradition: Pan-Orthodox (Church Father)

A Peace That Satisfied Neither Wing

The genius of the Formula of Reunion was also its fragility. It was a centrist document, a meeting in the middle: the East confessed Theotokos and the condemnation of Nestorius, and Alexandria accepted dyophysite, double-consubstantial language drawn from an Antiochene creed. Centrist settlements depend on the willingness of the extremes to be governed by the center, and on both flanks of this dispute there were men for whom the center was precisely the betrayal. The reconciliation of 433 therefore did not dissolve the controversy so much as relocate its fault lines, and the two cracks it opened would, in the following century, become the two great enduring schisms of Eastern Christianity (McGuckin, St. Cyril of Alexandria: The Christological Controversy, 107–125; Russell, Cyril of Alexandria, 50–53).

The Strict Cyrillians: “He Conceded Too Much”

The first storm came from Cyril’s own base. The zealous monks of Egypt and the strict Cyrillian party — the constituency that had cheered the Twelve Anathemas and prized “one incarnate nature of the Word” as the very banner of orthodoxy — were scandalized to see their champion subscribe to a creed that spoke of “two natures” and confessed Christ “consubstantial with us as to his manhood.” To them this was not nuance but capitulation: Cyril appeared to have abandoned the Anathemas, conceded the Antiochene point, and made peace with the men who had called his theology Apollinarian. This party — drawing on the same instincts that would later produce Eutyches, and the line of Alexandrian patriarchs running through Dioscorus — became the seedbed of the later Miaphysite (Oriental Orthodox) movement (McGuckin, 113–125; Russell, 50–52).

Cyril took the protest seriously, and his response defines much of his post-433 correspondence. He insisted, repeatedly and in writing, that he had not retracted the Twelve Anathemas and had conceded nothing essential. The Formula, he argued, was orthodox precisely because it confessed the one Christ, one Son, one Lord; the “two natures” of which it spoke were not two subjects, and the union remained a union in one hypostasis. His great defensive letters of this period make the case to anxious colleagues:

The Letter to Acacius of Melitene (Ep. 40, PG 77), addressed to a bishop sympathetic to the strict line, is the fullest apology, explaining at length why accepting the Easterners’ confession was no betrayal and how the language of two natures is to be rightly understood.
The Letter to Eulogius (Ep. 44, PG 77) defends the reunion to a Cyrillian agent at Constantinople, arguing that one should receive the orthodox sense of an opponent’s words rather than reject the words outright.
The two Letters to Succensus (Epp. 45–46, PG 77), bishop of Diocaesarea, are the most technically precise, working through the relation of the “one nature” idiom to the confession of two natures and refining the conceptual tools for holding both.

The conceptual key Cyril forged in these letters is the distinction between what is united in reality and distinguished only in contemplation (theoria). After the union, he argued, the two natures are not separated into two subjects existing apart; the union is real and concrete, issuing in one hypostasis. Yet the mind can still contemplate the difference between Godhead and manhood — the natures from which the one Christ is constituted remain distinguishable in thought, even though in concrete existence they are inseparably one. “Two natures” understood in theoria is therefore compatible with “one incarnate nature” understood as naming the single concrete subject. This theoria distinction is Cyril’s bridge between the Antiochene confession he had signed and his own settled vocabulary, and it would become a permanent fixture of later Cyrilline and neo-Chalcedonian thought (McGuckin, 113–125, 238–243; Russell, 51–53; Wessel, Cyril of Alexandria and the Nestorian Controversy, 268–274).

The Intransigent Antiochenes: “John Has Fallen Away”

The mirror-image protest came from the far side. Among the bishops of the East there were men for whom the condemnation of Nestorius was itself the apostasy — who held that Nestorius had taught nothing but the faith of the fathers and that to anathematize him was to anathematize the truth. When John of Antioch subscribed to the reunion, condemned Nestorius, and entered communion with Cyril, these intransigents declared that John himself had “fallen away from the faith,” and they broke communion with him rather than accept the settlement. They would not trade Nestorius for peace with Alexandria (McGuckin, 122–125; Russell, 50–52).

This dissident remnant was concentrated in the eastern provinces — the bishops of Cilicia and Euphratensis and the regions beyond, the old heartland of the Antiochene school. John and the imperial authorities applied pressure; some of the dissidents submitted, others were eventually deposed and went into schism or exile, and a number drifted eastward beyond the Roman frontier. This “Nestorianizing” remnant — those who continued to venerate Nestorius and the masters of the Antiochene tradition — fed, over the following decades, into the Church of the East, the so-called “Nestorian” Church of Persia and beyond, which would develop its own dyophysite Christology outside the imperial communion (McGuckin, 122–125; Russell, 51–52).

Two Schisms From One Settlement

The symmetry is exact and consequential. The Formula of Reunion bought peace between the two great sees by alienating the zealots of both wings simultaneously, and in doing so it planted the seeds of the two divisions that would permanently fracture Eastern Christianity:

On the Cyrillian flank, the strict party that thought Cyril had conceded too much became the nucleus of the Miaphysite / Oriental Orthodox churches, who would reject Chalcedon as a Nestorian betrayal.
On the Antiochene flank, the intransigents who thought John had conceded too much fed the East-Syrian / Church of the East, who would reject the condemnation of their teachers.

Both splits were latent in 433. The Formula’s very success as a centrist compromise — its refusal to give either extreme everything it wanted — is what made it the common ancestor of both later schisms. Peace at the center cost unity at the edges.

Cyril’s Own Hardening After 433

There is one further complication, and honesty requires stating it. Having signed the Formula and defended it as orthodox, Cyril himself did not rest comfortably in its dyophysite idiom in the years that followed. Under continuing pressure from his strict base — and in his ongoing polemic against the Antiochene theologians and the memory of Diodore and Theodore of Mopsuestia — Cyril increasingly re-emphasized the mia physis formula (“one incarnate nature of the Word”) in his later writings, foregrounding the unitive vocabulary that reassured his own party more than the two-natures language he had conceded to the East. He never repudiated the Formula, but the center of gravity of his late expression shifted back toward the single-nature idiom (McGuckin, 125, 226–243; Russell, 52–53, 191–200). [Disputed: how far this late emphasis represents a genuine theological hardening as opposed to a shift of rhetorical register for a different audience; scholars read the trajectory differently, and the question bears directly on the Christology treated in section 06.]

This later trajectory matters enormously for what followed, because it is Cyril’s mia physis writings, more than the Formula, that the Miaphysite tradition would canonize — and the gap between the Cyril who signed Laetentur caeli and the Cyril who pressed “one nature” is precisely the gap that the Chalcedonian and non-Chalcedonian readings of his legacy would later exploit. That reckoning belongs to the systematic Christology of the next section.

A Peace Held Together by One Man

The deepest lesson of 433 is the precariousness of the reunion. It rested not on a shared theology fully internalized by both communions but on a carefully balanced formula — and on the personal authority, prestige, and restraint of the men who had negotiated it, above all Cyril and John of Antioch. So long as Cyril lived, his stature could hold the center: he could reassure his own hardliners that nothing had been surrendered while honoring the communion he had granted the East. The settlement was, in a real sense, held together by one man’s authority and judgment.

That is also its tragedy. A peace that depends on a single towering figure does not easily survive him. After Cyril’s death in 444, with no one of comparable authority to interpret the Formula generously to both sides, the suppressed tensions broke open — in the rehabilitation of Eutyches, the violence of the Second Council of Ephesus in 449, and the great rupture at Chalcedon in 451. The cost of the peace of 433 was paid not only at the moment of reunion, in the alienation of the zealots, but across the following century, as the ambiguities the Formula had papered over hardened into the divisions of the Christian East.

References

Cyril of Alexandria, Letter to Acacius of Melitene (Ep. 40), PG 77; CPG 5340; trans. McGuckin and FC 76 (McEnerney), Letter 40.
Cyril of Alexandria, Letter to Eulogius (Ep. 44), PG 77; CPG 5344; trans. McGuckin and FC 76 (McEnerney), Letter 44.
Cyril of Alexandria, First and Second Letters to Succensus (Epp. 45–46), PG 77; CPG 5345–5346; trans. McGuckin (which prints both with commentary) and FC 76 (McEnerney), Letters 45–46.
Cyril of Alexandria, Letter to John of Antioch (Laetentur caeli), Ep. 39, PG 77, 173–181; CPG 5339; with the Formula of Reunion.
Eduard Schwartz, ed., Acta Conciliorum Oecumenicorum, tome 1: Concilium Universale Ephesenum (Berlin: de Gruyter, 1922–29); cited as ACO I.1.
John A. McGuckin, St. Cyril of Alexandria: The Christological Controversy (Crestwood, NY: SVS Press, 2004).
Norman Russell, Cyril of Alexandria (London: Routledge, 2000).
Susan Wessel, Cyril of Alexandria and the Nestorian Controversy (Oxford: Oxford University Press, 2004).