Constantinople's cathedral, destroyed in 404 by fire, is in 415 rebuilt by Theodosius II as the Great Church.

John Cassian soon afterwards tacitly permits the Pelagians to sack the monastery at Bethlehem, a center of vehement anti-Pelagianism, and is sharply reproved by Pope Innocent I.

Contention arises again in the Christian church over Pelagius' teaching that man is capable of leading a moral life without divine help.

Bishop John Cassian of Jerusalem receives him sympathetically in Palestine, but in July 415 the Latin biblical scholar Jerome and an emissary from Augustine of Hippo denounce him as heretical at the Jerusalem synod.

When Augustine's disciples invoke the authority of their master against Pelagius, John retorts that in Jerusalem he alone is the Christian authority.

He then devises a compromise formula, distasteful to Jerome, declaring that God can enable the earnest man to avoid sin.

Pelagius is judged free of doctrinal error, which is confirmed in December 415 at the metropolitan Council of Diospolis.

Orestes, the governor of Alexandria, clashes in 415 with the young bishop of Alexandria, Cyril, who had been appointed shortly before Orestes.

Orestes steadfastly resists Cyril's agenda of ecclesiastical encroachment into secular prerogatives.

Cyril on one occasion, sends the grammaticus Hierax to secretly discover the content of an edict that Orestes is to promulgate on the mimes shows, which attract great crowds.

When the Jews, with whom Cyril has clashed before, discover the presence of Hierax, they riot, complaining that Hierax's presence is aimed at provoking them.

Orestes then has Hierax seized and publicly tortured in the theater.

The Jews of Alexandria according to Christian sources scheme against the Christians and kill many of them.

Cyril reacts and expels either all of the Jews, or else only the murderers, from Alexandria, actually exerting a power that belongs to the civil officer, Orestes.

Orestes is powerless, but nonetheless rejects Cyril's gesture of offering him a Bible, which would mean that the religious authority of Cyril would require Orestes' acquiescence in the bishop's policy.

Approximately five hundred monks, who reside in the mountains of Nitria, have meanwhile heard of the ongoing feud between the Governor and Bishop, and shortly thereafter descend into Alexandria, armed and prepared to fight alongside Cyril.

These monks' violence had already been used by Theophilus fifteen years earlier against the "Tall Brothers"; furthermore, it is said that Cyril had spent five years among them in ascetic training.

The monks, upon their arrival in Alexandria, quickly intercept Orestes' chariot in town and proceed to bombard and harass him, calling him a pagan idolater.

Orestes responds to such allegations by countering that he is actually a Christian, and had even been baptized by Atticus, the Bishop of Constantinople.

The monks pay little attention to Orestes’ claims of Christianity, and one of the monks, by the name of Ammonius, strikes Orestes in the head with a rock, which causes him to bleed profusely.

Orestes’ guards at this point flee for fear of their lives, but a nearby crowd of Alexandrians come to his aid, and Ammonius is subsequently secured and ordered to be tortured for his actions.

Ammonius dies upon excessive torture; following his death, Cyril orders that he henceforth be remembered as a martyr.

Orestes is known to seek the counsel of Hypatia, and a rumor spreads among the Christian community of Alexandria in which she is blamed for his unwillingness to reconcile with Cyril.

Therefore, a mob of Christians gathers, led by a reader (i.e., a minor cleric) named Peter whom Scholasticus calls a fanatic.

They kidnap Hypatia on her way home and take her to the "Church called Caesareum. They then completely stripped her, and then murdered her with tiles".

Socrates Scholasticus was hence interpreted as saying that, while she was still alive, Hypatia's flesh was torn off using oyster shells (tiles; the Greek word is ostrakois, which literally means "oystershells" but the word was also used for brick tiles on the roofs of houses and for pottery sherds).

Afterward, the men proceed to mutilate her, and finally burn her limbs.

This political assassination eliminates an important and powerful supporter of the Imperial Prefect, and leads Orestes to give up his struggle against Patriarch Cyril and leave Alexandria.

Modern historians think that Orestes had cultivated his relationship with Hypatia to strengthen a bond with the pagan community of Alexandria, as he had done with the Jewish one, to handle better the difficult political life of the Egyptian capital.

When news breaks of Hypatia's murder, it provokes great public denouncement, not only against Cyril, but against the whole Alexandrian Christian community.

Cyril, who, if not directly responsible, at least had done nothing to prevent the riots, is forced to acknowledge the authority of the civil government.

The departure soon afterward of many scholars marks the beginning of the decline of Alexandria as a major center of ancient learning.

Constantius' blockade is effective: he drives the Visigoths out of Gaul.

He captures the usurper Priscus Attalus and sends him under military escort to Ravenna.

John Cassian, while he was in Rome, had accepted Pope Innocent’s invitation to found an Egyptian-style monastery in southern Gaul, near Marseille.

He may also have spent time as a priest in Antioch between 404 and 415.

Whatever the case, he arrives in Marseille around 415.

His foundation, the Abbey of St. Victor, is a complex of monasteries for both men and women, one of the first such institutes in the West, and will serve as a model for later monastic development.

Galla Placidia bears Ataulf a son, Theodosius, but his death in infancy destroys an opportunity for a possible Romano-Visigothic rapprochement.

Following Ataulf’s assassination at Barcelona later in the year while taking a bath, Sigeric succeeds him, but after a reign for seven days he is also murdered.

A new treaty with Rome, negotiated by Ataulf's successor Wallia, results in the widowed Placidia's return, with hostages, and a pledge by the Visigoths, in exchange for a supply of six hundred thousand measures of grain, to attack the Suebi, Alans and Vandals in Spain.

Ataulf's original aim had been to overthrow the Roman Empire, but, recognizing the inability of his people to govern an empire, he now desires to bolster Roman power by means of Gothic arms.

Having failed, however, to win recognition for his people as fœderati, or allies, of the empire, Ataulf retreats in early 415 into Tarraconensis in southern Spain, and captures Valencia.

The Jin general Liu Yu launches a major attack on Later Qin in 416, intending to destroy it.

As part of Liu Yu's force, a fleet commanded by the general Wang Zhongde, approaches Northern Wei's only main outpost south of the Yellow River, Huatai (in modern Anyang, Henan), the Northern Wei general Yuchi Jian, apprehensive of the Jin forces, abandons Huatai and flees back north of the Yellow River.

Emperor Mingyuan executes Yuchi and then sends messengers to rebuke Liu Yu and Wang Zhongde, both of whom restate that the target is Later Qin, not Northern Wei, and that the city will be returned as soon as the campaign was over. (Jin does not actually return Huatai, however, and Northern Wei will not have a major presence south of the Yellow River again until 422.)

Pelagius, responding in 416 to further attacks from Augustine and Jerome, writes De libero arbitrio (“On Free Will”), which results in the condemnation of his teaching by two African councils.