Helian Chang, for reasons not now known,…

Aspar, defeated in Africa by the Vandals, is forced to withdraw in 434, in which year he serves as consul.

Justa Grata Honoria, older sister of Valentinian, becomes pregnant from an officer in her household.

The liaison shakes the foundations of the Western Roman Empire.

Circles in the court at Ravenna assume inevitably that Honoria is planning to raise her paramour to imperial rank and challenge her brother.

Valentinian orders his execution.

Vincent of Lérins and the Commonitorium

In 434 CE, the Christian monk Vincent of Lérins (formerly of Auxerre) writes his Commonitorium (Memorandum), a collection of theological notes spanning thirty-three chapters. Wrestling with the complexities of doctrinal development, Vincent seeks to provide a systematic method for distinguishing authentic Christian tradition from heretical innovation.

The Vincentian Canon: A Triple Test for Orthodoxy

In the Commonitorium, Vincent argues that the Church must evaluate doctrine using a threefold test:

1. Ecumenicity – What has been believed by the whole Church.
2. Antiquity – What has been held from the earliest times.
3. Consent – What has been universally accepted by Church authorities.

This principle—summarized as “what has been believed everywhere, always, by all” (quod ubique, quod semper, quod ab omnibus creditum est)—becomes known as the Vincentian Canon. It will remain a foundational criterion for evaluating orthodoxy in both Western and Eastern Christianity for centuries.

Vincent’s Background and Historical Context

Little is known about Vincent’s early life, but he acknowledges having been engaged in secular pursuits, possibly in civil or military service, as implied by his phrase “secularis militia.” Eventually, he joins the monastic community on the island of Lérins, off the coast of southern Gaul, which serves as an important center of theological learning and ascetic practice in the Western Church.

Vincent references the Council of Ephesus, which was held in 431 CE, as having taken place “some three years earlier” (ante triennium ferme). This internal dating places the composition of the Commonitorium in 434 CE.

Influence and Legacy

The Commonitorium becomes one of the most influential theological works of the early medieval Church, shaping Western Christian thought on tradition, heresy, and doctrinal continuity. Though Vincent himself fades into obscurity, his Vincentian Canon remains a cornerstone of Christian theological methodology, invoked by later thinkers in debates on orthodoxy and doctrinal development.

The Huns under Rugila devastate Thrace and move steadily towards Constantinople.

The citizens prepare themselves for a long siege, depending on the strength of the Theodosian Walls.

Bleda and Attila, the two nephews of  the Hunnish leader Rugila, succeed him at his death in autumn 434, the military leadership having become hereditary.

The empire that Attila and his elder brother Bleda inherit seems to have stretched from the Alps and the Baltic in the west to somewhere near the Caspian Sea in the east.

Their first known action on becoming joint rulers is the negotiation of a peace treaty with the Eastern Roman Empire, which is concluded at the city of Margus (Pozarevac).

By the terms of the treaty, the Romans undertake to double the subsidies they have been paying to the Huns and in future to pay an immense annual tribute of about six hundred and sixty pounds (three hundred kilograms) of gold.

Attila and Bleda consolidate their power in the Hungarian capital, probably on the site of Buda (modern Budapest).

Feng Hong, in order to try to get Liu Song aid, sends a messenger in spring 435 to the Liu Song capital Jiankang to submit as a vassal.

Emperor Wen of Liu Song creates Feng Hong the Prince of Yan, but is unable to provide substantial aid.

Feng Hong now sends his general Tang Zhu to offer tribute to Northern Wei, and claiming illness as the reason that Feng Wangren is not coming.

This reason appears to have been rejected by Northern Wei, and Feng Hong again tries to seek Liu Song aid, but none is forthcoming.

In summer 435, Emperor Taiwu's brother Tuoba Pi, the Prince of Leping again arrives at Helong, and Feng Hong tries to appease him by offering cattle, wine, and armor, but Tuoba Pi's assistant general Qutu Yuan accuses Feng Hong of not sending hostages, and they seize six thousand Northern Yan men and women before withdrawing.

The entire Northern Yan state is by this point not significantly larger than the city of Helong itself, and it is weary of repeated Northern Wei attacks.

Feng Hong's general Yang Min suggests Feng Hong send Feng Wangren as a hostage but Feng Hong refused, instead considering a plan to evacuate his people to his ally Goguryeo.

Yang believes Goguryeo to be undependable but Feng Hong, not to be deterred, sends messengers to Goguryeo seeking aid and an agreement to harbor evacuees.

Emperor Theodosius II orders a new edict for the death penalty of all heretics and pagans in the Empire on November 1, 435.

Judaism is considered a legal non-Christian religion.

The Parthenon has survived for close to a thousand year as a temple dedicated to Athena until in 435, when Theodosius II decrees the closing all pagan temples in the Eastern Empire.

The Temple of Athena on the Acropolis of Athens is sacked and Athenian pagans are persecuted.

Athena's great cult image is looted by one of the emperors at some point in the fifth century and taken to Constantinople, where it will later be destroyed, possibly in 1204 during the siege of Constantinople during the Fourth Crusade.

John Cassian had come very late into writing and only does so when a request is made by an important person or persons.

His sources are the same as those of Evagrius Ponticus, who had been among his teachers, but he adds his own personal ideas, which are arranged in extensive collections.

Cassian writes two major spiritual works, the Institutions and the Conferences.

In these, he codifies and transmits the wisdom of the Desert Fathers of Egypt.

These books are written at the request of Castor, Bishop of Apt, of the subsequent Pope Leo I, and of several Gallic bishops and monks.

The Institutions (Latin: De institutis coenobiorum) deal with the external organization of monastic communities, while the Conferences (Latin: Collationes patrum in scetica eremo) deal with "the training of the inner man and the perfection of the heart."

In Books 1-4 of Institutions, Cassian discusses clothing, prayer and rules of monastic life.

Books 5-12 are rules on morality, specifically addressing the eight vices - gluttony, lust, avarice, hubris, wrath, envy, acedia, and boasting - and what to do to cure these vices.

The Conferences, dedicated to Pope Leo, to the bishop of Frejus, and to the monk Helladius, summarize important conversations that Cassian had had with elders from Scetis about principles of the spiritual and ascetic life.

This book addresses specific problems of spiritual theology and the ascetic life.

It will later be read in Benedictine communities before a light meal, and from the Latin title, Collationes, comes the word collation in the sense of "light meal."

His third book, On the Incarnation of the Lord, is a defense of orthodox doctrine against the views of Nestorius, and is written at the request of the Archdeacon of Rome, later Pope Leo I.

His books, written in Latin, in a simple, direct style, are swiftly translated into Greek, for the use of Eastern monks, an unusual honor.

He dies in the year 435 in Marseille.

John Cassian's abbey and writings will influence St. Benedict, who will incorporate many of the same principles into his monastic rule (Rule of St. Benedict), and recommend to his own monks that they read the works of Cassian.

(Since Benedict's rule is still used by Benedictine, Cistercian, and Trappist monks, the thought of John Cassian still guides the spiritual lives of thousands of men and women in the Western Church.)

Aetius receives the title of patrician in 435.