The idea of this great council seems to have been due to Nestorius, the Bishop of Constantinople. St. Cyril, Patriarch of Alexandria, had accused him to Pope St. Celestine of heresy, and the pope had replied on 11 August, 430, by charging St. Cyril to assume his authority and give notice in his name to Nestorius that, unless he recanted within ten days of receiving this ultimatum, he was to consider himself excommunicated and deposed. The summons was served on Nestorius on a Sunday, 30 November, or 7 December, by four bishops sent by Cyril. But Nestorius was evidently well informed of what he was to expect. He regarded himself as having been calumniated to the pope, and he did not choose to be given over into the hands of Cyril. The latter was, in his opinion, not merely a personal enemy, but a dangerous theologian, who was reviving to some extent the errors of Apollinarius. Nestorius had influence over the Emperor of the East, Theodosius II, whom he induced to summon a general council to judge of the difference between the Patriarch of Alexandria and himself, and he worked so well that the letters of convocation were issued by the emperor to all metropolitans on 19 November, some days before the messengers of Cyril arrived. The emperor was able to take this course without seeming to favour Nestorius too much, because the monks of the capital, whom Nestorius had excommunicated for their opposition to his heretical teaching, had also appealed to him to call together a council. Nestorius, therefore, paid no attention to the pope's ultimatum, and refused to be guided by the advice to submit which his friend John, the Patriarch of Antioch, volunteered.

The pope was pleased that the whole East should be united to condemn the new heresy. He sent two bishops, Arcadius and Projectus, to represent himself and his Roman council, and the Roman priest, Philip, as his personal representative. Philip, therefore, takes the first place, though, not being a bishop, he could not preside. It was probably a matter of course that the Patriarch of Alexandria should be president. The legates were directed not to take part in the discussions, but to give judgment on them. It seems that Chalcedon, twenty years later, set the precedent that the papal legates should always be technically presidents at an ecumenical council, and this was henceforth looked upon as a matter of course, and Greek historians assumed that it must have been the case at Nicaea.

The emperor was anxious for the presence of the most venerated prelate of the whole world, Augustine, and sent a special messenger to that great man with a letter in honourable terms. But the saint had died during the siege of Hippo in the preceding August, though the troubles of Africa had prevented news from reaching Constantinople.

Theodosius wrote an angry letter to Cyril, and a temperate one to the council. The tone of the latter epistle and of the instructions given to the imperial commander, Count Candidian, to be absolutely impartial, are ascribed by the Coptic Acts to the influence exercised on the emperor by the Abbot Victor, who had been sent to Constantinople by Cyril to act as his agent at the Court on account of the veneration and friendship which Theodosius was known to feel for the holy man.

Nestorius, with sixteen bishops, and Cyril, with fifty, arrived before Pentecost at Ephesus. The Coptic tells us that the two parties arrived on the same day, and that in the evening Nestorius proposed that all should join in the Vesper service together. The other bishops refused. Memnon, Bishop of Ephesus, was afraid of violence, and sent his clergy only to the church. The mention of a Flavian, who seems to be the Bishop of Philippi, casts some doubt on this story, for that bishop did not arrive till later. Memnon of Ephesus had forty suffragans present, not counting twelve from Pamphylia (whom John of Antioch calls heretics). Juvenal of Jerusalem, with the neighbouring bishops whom he looked upon as his suffragans, and Flavian of Philippi, with a contingent from the countries which looked to Thessalonica as their metropolis, arrived soon after Pentecost. The Patriarch of Antioch, John, an old friend of Nestorius, wrote to explain that his suffragans had not been able to start till after the Octave of Easter. (The Coptic Acts say that there was a famine at Antioch.) The journey of thirty days had been lengthened by the death of some horses; he would accomplish the last five or six stages at leisure. But he did not arrive, and it was said that he was loitering because he did not wish to join in condemning Nestorius. Meanwhile the heat was great. Many bishops were ill. Two or three died. Two of John's metropolitans, those of Apamea and Hierapolis, arrived and declared that John did not wish the opening of the council to be deferred on account of his delay. However, these two bishops and Theodoret of Cyrus, with sixty-five others, wrote a memorial addressed to St. Cyril and Juvenal of Jerusalem, begging that the arrival of John should be awaited. Count Candidian arrived, with the imperial decree, and he took the same view.

But Cyril and the majority determined to open the council on 22 June, sixteen days having passed since John had announced his arrival in five or six. It was clear to the majority that this delay was intentional, and they were probably right. Yet it is regrettable that all possible allowance was not made, especially as no news had yet come from Rome. For Cyril had written to the pope with regard to an important question of procedure. Nestorius had not recanted within the ten days fixed by the pope, and he was consequently treated as excommunicate by the majority of the bishops. Was he to be allowed a fresh trial, although the pope had already condemned him? Or, on the other hand, was he to be merely given the opportunity of explaining or excusing his contumacy? One might have presumed that Pope Celestine, in approving of the council, intended that Nestorius should have a full trial, and in fact this was declared in his letter which was still on the way. But as no reply had come to Cyril, that saint considered that he had no right to treat the pope's sentence as a matter for further discussion, and no doubt he had not much wish to do so.

First Session (June 22)

The council assembled on 22 June, and St. Cyril assumed the presidency both as Patriarch of Alexandria and "as filling the place of the most holy and blessed Archbishop of the Roman Church, Celestine", in order to carry out his original commission, which he considered, in the absence of any reply from Rome, to be still in force.

In the morning 160 bishops were present, and by evening 198 had assembled. The session began by a justification of the decision to delay no longer. Nestorius had been on the previous day invited to attend. He had replied that he would come if he chose. To a second summons, which was now dispatched, he sent a message from his house, which was surrounded with armed men, that he would appear when all the bishops had come together. Indeed only some twenty of the sixty-eight who had demanded a delay had rallied to Cyril, and Nestorius's own suffragans had also stayed away. To a third summons he gave no answer. This attitude corresponds with his original attitude to the ultimatum sent by Cyril. He would not acknowledge Cyril as a judge, and he looked upon the opening of the council before the arrival of his friends from Antioch as a flagrant injustice.

The session proceeded. The Nicene Creed was read, and then the second letter of Cyril to Nestorius, on which the bishops at Cyril's desire, severally gave their judgment that it was in accordance with the Nicene faith, 126 speaking in turn. Next the reply of Nestorius was read. All then cried Anathema to Nestorius. Then Pope Celestine's letter to St. Cyril was read, and after it the third letter of Cyril to Nestorius, with the anathematisms which the heretic was to accept. The bishops who had served this ultimatum on Nestorius deposed that they had given him the letter. He had promised his answer on the morrow, but had not given any, and did not even admit them.

Then two friends of Nestorius, Theodotus of Ancyra and Acacius of Mitylene, were invited by Cyril to give an account of their conversations at Ephesus with Nestorius. Acacius said that Nestorius had repeatedly declared dimeniaion e trimeniaion me dein legesthai Theon. Nestorius's own account of this conversation in his "Apology" (Bethune-Baker, p. 71) shows that this phrase is to be translated thus: "We must not say that God is two or three months old." This is not so shocking as the meaning which has usually been ascribed to the words in modern as well as ancient times (e.g. by Socrates, VII, xxxiv): "A baby of two or three months old ought not to be called God." The former sense agrees with the accusation of Acacius that Nestorius declared "one must either deny the Godhead (theotes) of the Only-begotten to have become man, or else admit the same of the Father and of the Holy Ghost." (Nestorius means that the Divine Nature is numerically one; and if Nestorius really said theotes, and not hypostasis, he was right, and Acacius was wrong.)

Acacius further accused him of uttering the heresy that the Son who died is to be distinguished from the Word of God. A series of extracts from the holy Fathers was then read, Peter I and Athanasius of Alexandria, Julius and Felix of Rome (but these papal letters were Apollinarian forgeries), Theophilus, Cyril's uncle, Cyprian, Ambrose, Gregory Nazianzen, Basil, Gregory of Nyssa, Atticus, Amphilochius. After these, contrasted passages from the writings of Nestorius were read. These were of course pièces justificatives brought forward by Cyril, and necessary to inform the council as to the question at issue. Hefele has wrongly understood that the bishops were examining the doctrine of Nestorius afresh, without accepting the condemnation of the pope as necessarily correct. A fine letter from Capreolus, Bishop of Carthage, and primate of a greater number of bishops than any of the Eastern patriarchs, was next produced. He writes in the midst of the devastation of Africa by the Vandals, and naturally could neither hold any synod nor send any bishops. No discussion followed (and Hefele is wrong in suggesting an omission in the Acts, which are already of extraordinary length for a single day), but the bishops accepted with acclamation the words of Capreolus against novelty and in praise of ancient faith, and all proceeded to sign the sentence against Nestorius. As the excommunication by St. Celestine was still in force, and as Nestorius had contumaciously refused to answer the threefold summons enjoined by the canons, the sentence was worded as follows:

The holy synod said: "Since in addition to the rest the most impious Nestorius has neither been willing to obey our citation, nor to receive the most holy and god-fearing bishops whom we sent to him, we have necessarily betaken ourselves to the examination of his impieties; and, having apprehended from his letters and from his writings, and from his recent sayings in this metropolis which have been reported, that his opinions and teachings are impious, we being necessarily impelled thereto both by the canons [for his contumacy] and by the letter [to Cyril] of our most holy father and colleague Celestine, Bishop of the Roman Church, with many tears have arrived at the following grievous sentence against him: Our Lord, Jesus Christ, Who has been blasphemed by him, has defined by this holy synod that the same Nestorius is excluded from all episcopal dignity and from every assembly of bishops.

Arrival of John of Antioch (June 27)

Five days after the first session John of Antioch arrived. The party of Cyril sent a deputation to meet him honourably, but John was surrounded by soldiers, and complained that the bishops were creating a disturbance. Before he would speak to them, he held an assembly which he designated "the holy synod". Candidian deposed that he had disapproved of the assembling of the bishops before John's arrival; he had attended the session and read the emperor's letter (of this not a word in the Acts, so Candidian was apparently lying). John accused Memnon of violence, and Cyril of Arian, Apollinarian, and Eunomian heresy. These two were deposed by forty-three bishops present; the members of the council were to be forgiven, provided they would condemn the twelve anathematisms of Cyril. This was absurd, for most of these could not be understood in anything but a Catholic sense. But John, who was not a bad man, was in a bad temper. It is noticeable that not a word was said in favour of Nestorius at this assembly. The party of Cyril was now complaining of Count Candidian and his soldiers, as the other side did of Memnon and the populace. Both parties sent their report to Rome. The emperor was much distressed at the division, and wrote that a collective session must be held, and the matter begun afresh. The official named Palladius who brought this epistle took back with him many letters from both sides. Cyril proposed that the emperor should send for him and five bishops, to render an exact account.

Second Session (10 July)

At last on 10 July the papal envoys arrived. The second session assembled in the episcopal residence. The legate Philip opened the proceedings by saying that the former letter of St. Celestine had been already read, in which he had decided the present question; the pope had now sent another letter. This was read. It contained a general exhortation to the council, and concluded by saying that the legates had instructions to carry out what the pope had formerly decided; doubtless the council would agree. The Fathers then cried:

This is a just judgment. To Celestine the new Paul! To the new Paul Cyril! To Celestine, the guardian of the Faith! To Celestine agreeing to the Synod! The Synod gives thanks to Cyril. One Celestine, one Cyril!

Third Session (July 11)

On the following day, 11 July, the third session took place. The legates had read the Acts of the first session and now demanded only that the condemnation of Nestorius should be formally read in their presence. When this had been done, the three legates severally pronounced a confirmation in the pope's name. The exordium of the speech of Philip is celebrated:

It is doubtful to none, nay it has been known to all ages, that holy and blessed Peter, the prince and head of the Apostles, the column of the Faith, the foundation of the Catholic Church, received from our Lord Jesus Christ, the Saviour and Redeemer of the human race, the keys of the Kingdom, and that to him was given the power of binding and loosing sins, who until this day and for ever lives and judges in his successors. His successor in order and his representative, our holy and most blessed Pope Celestine. . .

Fourth session (July 16)

On 16 July a more solemn session was held, like the first, in the cathedral of the Theotokos. Cyril and Memnon presented a written protest against the conciliabulum of John of Antioch. He was cited to appear, but would not even admit the envoys.

Fifth Session (July 17)

Next day the fifth session was held in the same church. John had set up a placard in the city accusing the synod of the Apollinarian heresy. He is again cited, and this is counted as the third canonical summons. He would pay no attention. In consequence the council suspended and excommunicated him, together with thirty-four bishops of his party, but refrained from deposing them. Some of John's party had already deserted him, and he had gained only a few. In the letters to the emperor and the pope which were then dispatched, the synod described itself as now consisting of 210 bishops. The long letter to Celestine give a full account of the council, and mentions that the pope's decrees against the Pelagians had been read and confirmed.

Sixth Session

At the end of the sixth session, which dealt only with the case of two Nestorianizing priests, was made the famous declaration that no one must produce or compose any other creed than (para, proeter, "beyond" -- "contrary to"?) the Nicene, and that anyone who should propose any such to pagans, Jews, or heretics, who wished to be converted, should be deposed if a bishop or cleric, or anathematized if a layman. This decision became later a fruitful source of objections to the decrees of later synods and to the addition of the filioque to the so-called Constantinopolitan Creed; but that creed itself would be abolished by this decree if it is taken too literally. We know of several matters connected with Pamphylia and Thrace which were treated by the council, which are not found in the Acts. St. Leo tells us that Cyril reported to the pope the intrigues by which Juvenal of Jerusalem tried at Ephesus to carve himself a patriarchate out of that of Antioch, in which his see lay. He was to succeed in this twenty years later, at Chalcedon.

Seventh Session (July 31)

In the seventh and last session on 31 July (it seems) the bishops of Cyprus persuaded the council to approve their claim of having been anciently and rightly exempt from the jurisdiction of Antioch. Six canons were also passed against the adherents and supporters of Nestorius.

The history of the intrigues by which both parties tried to get the emperor on their side need not be detailed here. The orthodox were triumphant at Ephesus by their numbers and by the agreement of the papal legates. The population of Ephesus was on their side. The people of Constantinople rejoiced at the deposition of their heretical bishop. But Count Candidian and his troops were on the side of Nestorius, whose friend, Count Irenaeus, was also at Ephesus, working for him. The emperor had always championed Nestorius, but had been somewhat shaken by the reports of the council. Communication with Constantinople was impeded both by the friends of Nestorius there and by Candidian at Ephesus. A letter was taken to Constantinople at last in a hollow cane, by a messenger disguised as a beggar, in which the miserable condition of the bishops at Ephesus was described, scarce a day passing without a funeral, and entreaty was made that they might be allowed to send representatives to the emperor. The holy abbot, St. Dalmatius, to whom the letter was addressed, as well as to the emperor, clergy, and people of Constantinople, left his monastery in obedience to a Divine voice and, at the head of the many thousand monks of the city, all chanting and carrying tapers, made his way through enthusiastic crowds to the palace. They passed back right through the city, after the abbot Dalmatius had interviewed the emperor, and the letter was read to the people in the church of St. Mocius. All shouted "Anathema to Nestorius!"

Eventually the pious and well-meaning emperor arrived at the extraordinary decision that he should ratify the depositions decreed by both councils. He therefore declared that Cyril, Memnon, and John were all deposed. Memnon and Cyril were kept in close confinement. But in spite of all the exertions of the Antiochan party, the representatives of the envoys whom the council was eventually allowed to send, with the legate Philip, to the Court, persuaded the emperor to accept the great council as the true one. Nestorius anticipated his fate by requesting permission to retire to his former monastery. The synod was dissolved about the beginning of October, and Cyril arrived amid much joy at Alexandria on 30 October. St. Celestine was now dead, but his successor, St. Sixtus III, confirmed the council.