It is difficult to harmonize the accounts of his character. Theodoret, whose testimony in his favor cannot be suspected, writes to Dioscorus, soon after Dioscurus' consecration, that the fame of his virtues, and particularly of his modesty and humility, was widely known (Ep. 60). He had served as Cyril's archdeacon. Liberatus says that he had never been married. On the other hand, after he had involved himself in the Monophysite heresy, he was accused of serious misconduct in the first years of his episcopate. The deacon Ischyrion, Cyril's nephew Athanasius, and one Sophronius all recounted his misconduct: misapropriation of money, associating with prostitutes, encouraging physical attacks, misuse of the legal system and his influence with the court to impoverish his opponents. "The country," said Sophronius, "belonged to him rather than to the sovereigns". While such accusations against Dioscorus when he was on trial himself are likely to be exaggerated, or properly the work of uncontrolled agents, there is sufficient truth in them to indicate that his elevation to the Patriarchate corrupted him; for such, in those days, was the great "evangelical throne."
A letter survives addressed to him from Pope Leo the Great, who wrote on June 21, 445, that "it would be shocking to believe that St. Mark formed his rules for Alexandria otherwise than on the model of St. Peter" (Ep. 11). In 447 Dioscorus appears among those suspicious of the orthodoxy of Theodoret, who had been identified as part of the party of Nestorius. Rumor had come to Dioscorus that Theodoret, preaching at Antioch, had practically taught Nestorianism, and hearing this, he wrote to Domnus II, patriarch of Antioch, Theodoret's patriarch. Theodoret answered with a denial which included an anathema against all who professed the tenets of Nestorianism: denying the Holy Virgin to be Theotokos, calling Jesus a mere man, or dividing the one Son into two. Dioscorus was not convinced (Theod. Ep. 86), and allowed Theodoret to be anathematized in church, and even rose from his throne to echo the malediction, and sent a deputation to Constantinople against Theodoret.
Then in November 448, the aged Eutyches, archimandrite of Constantinople and a vehement enemy of the Nestorians, was accused by Eusebius, bishop of Dorylaeum, before a synod under Flavian's presidency, with the opposite error. He clung tenaciously to the phrase, "one incarnate nature of God the Word," which Cyril had used on the authority of Athanasius of Alexandria, but neglected to include the qualifications that Cyril had included. Thus Eutyches appeared to have revived the Apollinarian heresy - whereupon he was defrocked and excommunicated. His patron, the chamberlain Chrysaphius, applied to Dioscorus for aid, promising his support at the capital in exchange for his help with Eutyches. Eutyches himself wrote to Dioscorus, asking him "to examine his cause" (Liberat. c. 12), and Dioscorus, zealous to protect the reputation of his predecessor, wrote to the emperor to ask for a general council to review Flavian's judgment. Theodosius II, influenced by both wife and chamberlain, issued letters (March 30, 449), ordering the chief prelates and bishops to meet at Ephesus by August 1, 449 (Mansi, vi. 587).
This council - which Leo afterwards named "Latrocinium," or "Robber Council" - met on August 8, 449, in St. Mary's church at Ephesus, the scene of the third general council's meeting in 431; 150 bishops being present. Dioscorus presided, and next to him Julian and Hilarius, the papal legates, then Juvenal of Jerusalem, Domnus II of Antioch, and - his lowered position indicating what was to come - Flavian of Constantinople.
The archbishop of Alexandria did indeed propose the acceptance of Leo's letter to the council, a letter expressly referring to, the famous "Tome" of Pope Leo, but it was only handed in, not read. Juvenal moved that another imperial letter should be read and recorded. The president then announced that the council's business was not to frame a new doctrinal formulary, but to hold an inquest concerning the statements of Flavian and bishop Eusebius on the one hand, those of Eutyches on the other, and determine whether they were in accord with the decisions of the councils of Nicaea and Ephesus - "two councils in name," said he, "but one in faith" (ib. 628). Eutyches was allowed to make his statement; but when Flavian asked that Eusebius be heard, who had been his accuser, Elpidius, the imperial commissioner, vetoed this request - with the support of Dioscorus. The legates again urged that "the pope's letter" should be read first, but this was overruled; the "acts of the synod" were read, but the reading was calculated to make the earlier synod apear to profess the heresy of Nestorianism, and Eutyches to profess undeniable orthodoxy. Dioscorus' Egyptian followers contributed by cheering the words of Eucyhes and voicing anger at the words of Fabian's inquest. Dioscorus then called on the bishops to give their verdict as to the theological statements of Eutyches.
They acquitted Eutyches of all unsoundness, and faithful to Nicene and Ephesian teaching. Domnus expressed regret for having mistakenly condemned him; Basil of Seleucia spoke like the rest. Flavian was silent. Dioscorus spoke last, affirming the judgments of the council. Eutyches was "restored" to his former rank and dignity and his monks released from excommunication. Dioscorus proposed that the doctrinal decisions of the Council of Ephesus of 431, in its first and sixth sessions, with those of Nicaea, should be recognized as an unalterable standard of orthodoxy; that whoever should say or think otherwise, should be put under censure. Several bishops assented. Hilarius, the Roman deacon, testified that the apostolic see reverenced those decisions, and that its letter, if read, would prove this.
Dioscorus called in some imperial notaries, who brought forward a draft sentence of deposition against Flavian and Eusebius, on the ground that the Ephesian council had enacted severe penalties against any who should propose an alternate creed to the Nicene. Flavian and Eusebius were declared to have committed this offence by "unsettling almost everything, and causing scandal and confusion throughout the churches." Onesiphorus, bishop of Iconium, with some others, went up to Dioscorus, clasped his feet and knees, and begged Dioscorus for leniency on behalf of the two bishops, but to no avail. Dioscorus called to the soldiers, and upon their enterance he commanded the bishops to sign the sentence, and with a fierce gesture of the hand threatened those prelates who were reluctant to agree to the deposition with exile, beatings from the soldiers, denounced as heretics by the partisans of Dioscorus, and by the fanatical monks led by Barsumas. Basil of Seleucia later stated he signed the deposition because he was "given over to the judgment of 120 or 130 bishops; had he been dealing with magistrates, he would have suffered martyrdom."
Flavian had sent by the Roman delegates a formal appeal to the pope and the Western bishops, but this was nearly his last act. He was brutally treated, kicked, and beaten by the agents of Dioscorus, and even, we are told, by Dioscorus himself (see Evagr. i. 1; Niceph. xiv. 47). He was then imprisoned, and sentenced to be exiled, but died from the effect of his injuries three days after his deposition (Liberatus, Brev. 19), on August 11, 449. He was regarded as a martyr for the doctrine of "the two natures in the one person" of Christ. Anatolius, who had been the agent (apocrisiariuV) of Dioscorus at Constantinople, was appointed his successor.
Firmly in control of this council, Dioscorus proceeded to depose Theodoret and several other bishops; "many," says Leo, "were expelled from their sees, and banished, because they would not accept heresy" (Ep. 93). Theodoret was put under a special ban. "They ordered me," he writes (Ep. 140), "to be excluded from shelter, from water, from everything."
Confusion now pervaded the Eastern churches. Leo sought a new ecumenical council, to be convened in Italy: both the emperor Valentinian III and his mother Galla Placidia in the West supported this, but Theodosius II persisted in upholding the recent council. In the spring of 450 Dioscorus took a new and exceptionally audacious step. At Nicaea, on his way to the court, he ordered ten bishops whom he had brought from Egypt to sign a document excommunicating pope Leo, doubtlessly in response to Leo's attempts to reverse the acts of his council. His ability to enforce the acts of this council, however, greatly weakened in the following months. First was the fall of his patron Chrysaphius in the summer of 450; next was the death of Theodosius II, and the marriage of the orthodox Pulcheria, sister of Theodosius, to Marcian, enabling her to push for the new council that met at Chalcedon on October 8, 451.
The first session of the council was devoted to an inquest of Dioscorus' actions. The charges were read by Beronicianus, the secretary of the imperial consistory, to the assembled bishops. At various points the members shouted in protest at the records, claiming that they had been coerced with threats to agree, or had been misquoted, and at the autocratic manner Discorus had ruled the proceedings. To all of these accusations Dioscorus calmly and elequently responded, conceding not one point but meeting all of them directly.
The proceedings turned to Dioscorus' own actions, why he received communion with Eutyches, and his treatment of Flavian. The climax came when asked "Why then did you depose Flavian?" Dioscorus anwered "I erred." Flavian's own statement was considered; several bishops in turn ruled it acceptable, including Paschasinus, Anatolius, Maximus, Thalassius, and Eustathius. Some from the Eastern churches began to speak of Flavian as a martyr. "Let his next words be read," said Dioscorus; "you will find that he is inconsistent with himself." As if in response Juvenal, who had been sitting on the right, now went over to the left, and the Easterns welcomed him. Peter of Corinth, a young bishop, did the same, stating that Flavian held with Cyril; the Easterns exclaimed, "Peter thinks as does [Saint] Peter." Other bishops spoke similarly.
The reading continued until it was necessary to light the candles. Dioiscorus continued to defend himself, but in vain. At last they came to the signatures affixed to the deposition; then the magistrates proposed that as the deposition had been proved unjust, Dioscorus, Juvenal, Thalassius, Eusebius of Ancyra, Eustathius, and Basil, as leaders in the late synod, should be deposed; but this, it appears was a provisional sentence, to be further considered by the council. The magistrates desired that each bishop should submit a statement of belief conforming to the Nicene "exposition," to that of the 150 Fathers (of Constantinople, in 381), to the canonical epistles and expositions of the Church Fathers and Cyril's two canonical epistles published and confirmed in the first Ephesian council, adding that Leo had written a letter to Flavian against Eutyches.
Dioscorus avoided attending the next two sessions. When summoned to attend, at first he said that he was willing to come, but his guards prevented him. After the council sent two more summonses, he made it clear that he refused to come. He had nothing more to say than he had said to former envoys: "What I have said, I have said; it is enough." The messengers left to report their failure. "Do you order that we proceed to ecclesiastical penalties against him?" asked Paschasinus, addressing the council. "Yes, we agree." One bishop said bittterly, "When he murdered holy Flavian, he did not adduce canons, nor proceed by church forms." In his absence, Dioscorus was deposed as bishop, and stripped of is priesthood. A letter was written to Dioscorus, informing him of this act.
Dioscorus at first made light of the sentence, saying he would soon be restored. The council wrote to the two emperors, reciting his misdeeds, and informing them of the synod's sentence. The emperor comfirmed this deposition; Dioscorus was banished to Gangra in Paphlagonia, dying there in 454. Proterius, archpriest of Alexandria, who adhered to the council of Chalcedon, was placed in the see of St. Mark, but never gained the goodwill of his congregation, who regarded Dioscorus as their legitimate patriarch. Dioscorus' deposition inaugurated the schism which to this day has divided the Christians of Egypt, the majority of whom, bearing the name of Jacobites, have always disowned the council of Chalcedon, and venerated Dioscorus as "their teacher" (Lit. Copt. St. Basil), and as a persecuted saint (see Neale, Hist. Alex. ii. 6).