Theodosius I (FLAVIUS THEODOSIUS), Roman Emperor, b. in Spain, about 346; d. at Milan, January 17, 395. Theodosius is one of the sovereigns by universal consent called Great. He stamped out the last vestiges of paganism, put an end to the Arian heresy in the empire, pacified the Goths, left a famous example of penitence for a crime, and reigned as a just and mighty Catholic emperor. His father, the Comes Theodosius, was a distinguished general; both he and the mother Thermantia were Catholics at a time when Arianism was at its strongest. Theodosius the son distinguished himself in the army, was made Dux of Moesia, defeated the Sarmatians (Ammianus Marcellinus, XXIX, 6); then, when an intrigue brought about the disgrace and execution of his father (376) he retired to his own property in Spain. But his reputation was not forgotten. The Emperor Gratian (375-383) after the death of Valens (378) took Theodosius from private life and made him his fellow-emperor (Augustus) for the East (January 19, 379). He was already married to “Elea Flacilla, by whom he had two sons, Arcadius and Honorius (his future successors) and a daughter Pulcheria. As Augustus he carried on the Gothic war vigorously and successfully. During the year 380 he was able to conclude a victorious peace with the Goths; on November 24 he held his triumph at Constantinople. Meanwhile he had also repressed the Vandals and Huns. Early in the same year a severe sickness at Thessalonica made him seek baptism, and he was baptized by the Catholic Bishop of Thessalonica, Ascholios. Socrates (H. E., V, 6) says that since Theodosius “was a Christian from his parents and professed the faith of the Homoousios” he first assured himself that the bishop was not an Arian (cf. Sozomen; “H. E.”, VII, 4). A great part of the emperor’s activity was now spent in establishing the Catholic faith and repressing Arianism. In February, 380, he and Gratian published the famous edict that all their subjects should profess the faith of the Bishops of Rome and Alexandria (Cod. Theod., XVI, 1, 2; Sozomen, VII, 4). The conventicles of the heretics were not to be called churches.
As soon as he came to Constantinople Theodosius began expelling the Arians, who had hitherto been in possession. The Arian bishop, Demophilus, left the city (Socr., V, 7; Soz., VII, 5), St. Gregory of Nazianzus undertook the administration of the diocese. In January, 381, the prefect had orders to close all Arian chapels in the city and to expel those who served them. The same severe measures were ordered throughout Theodosius’s dominion, not only against Arians, but also in the case of Manichaeans and all other heretics. However Sozomen says that the emperor “made severe punishments by his laws, but did not carry them out, for he did not wish to punish, but only to frighten his subjects, that they might think as he did about Divine things. And he praised those who were converted of their own accord” (H. E., VII, 12). In 381 the Second General Council was held at Constantinople under his auspices (Socr., V, 8; Soz., VII, 7). In 383 he attempted a conference at his capital between Catholics and Arians, with a view to a reconciliation; but no result was obtained (Socr., V, 10; Soz., VII, 12). In the same year Gratian was murdered at Lyons (August 25) and Clemens Maximus usurped the imperial title in the West (383-388). Theodosius acknowledged the usurper on condition that he would allow Gratian’s brother, Valentinian II, to reign in Italy. In 387 Maximus broke the contract and expelled Valentinian, who fled to Theodosius. Theodosius brought him back with an army, and defeated and executed Maximus at Aquileia. Valentinian II now reigned in the West till 392. It was also in 387 that Theodosius showed such tolerance in the affair of the statues at Antioch (see Saint John Chrysostom).
During all his reign Theodosius took severe measures against the surviving remnants of paganism. In 388 a prefect was sent around Egypt, Syria, and Asia Minor for the purpose of destroying temples and breaking up pagan associations; it was then that the Serapeum at Alexandria was destroyed (Socr., V, 16). Libanius wrote a “Lamentation” about the destruction of the fanes of the gods (peri ton hieron, ed. R. Foerster, Bibl. Script. Gr. et Rom. Teubner). In 391 Theodosius refused to allow the Altar of Victory to be restored in the Roman Senate (cf. Gibbon, “Decline and Fall”, xxviii). Pagan sacrifices, omens, and witchcraft were to be punished as laesa majestas (Cod. Theod., XVI, X, 10-12). In short his laws put an end finally to the old cult, at any rate as far as open and public use is concerned. One of its last acts was a despairing appeal to the sword, which offers again the dramatic situation of a field of battle on which the religion of Europe seemed to depend. Argobast, the Frankish tutor of Valentinian II, at least indirectly caused his ward’s death (Hodgkin, “Italy and her Invaders”, I, 590) and set up a rhetorician, Eugenius, in his stead (May 15, 392). Theodosius hastened to Italy to avenge this crime. Eugenius, although nominally a Christian, tried to unite the remains of paganism in his defense. He set up pagan altars again (including that of Victory at Rome), his soldiers marched under the standard of Hercules invictus. But near Aquileia on September 6, 394, once more the Christian Labarum triumphed over the banner of the ancient gods; Theodosius entered Rome sole master of the now finally Christian empire. Further laws enforced the keeping of Sunday and the disabilities of pagans, Jews, and heretics. During the greater part of his reign Theodosius was in intimate relation with St. Ambrose. The story of the emperor’s worst crime, the massacre of at least 7000 citizens of Thessalonica in revenge for a tumult (April, 390); of St. Ambrose’s refusal to allow him to enter the Church; of his acceptance of eight months of penance, is one of the memorable incidents of Church history.
Theodosius married Galla (daughter of Valentinian I) after the death of his first wife, and by her had a daughter, Galla Placidia, the mother of Valentinian III. St. Ambrose preached his funeral oration (“De obitu Theodosii”, P.L., XVI, 1385). His two sons Arcadius and Honorius had already been proclaimed Augustus during his life. Arcadius became emperor of the eastern half of the empire, Honorius of the western. The Roman world was never again united. Theodosius stands out as the destroyer of heresy and paganism, as the last sovereign of the undivided empire. A coin representing him holding the Labarum with the inscription, Restitutor Reipublicae, expresses perfectly his title to remembrance.