The ecclesiastical history presents the Christian empire from Constantine to the early fifth century as a field in which doctrinal conflict, imperial policy, ascetic holiness, persecution, and divine providence intersect. It recounts Constantine’s conversion, the Council of Nicaea’s confession of the Son’s consubstantiality with the Father, the discovery of the True Cross, the building of Constantinople and Jerusalem’s Great Martyrium, and the spread of Christianity alongside persecution in Persia. The careers of Athanasius, Alexander, Hosius, Spyridon, Antony, Pachomius, and other bishops and ascetics illustrate resistance to Arian and related teachings.

Successive emperors alternately protect and suppress Nicene Christians. Councils at Sardica, Ariminum, Seleucia, Lampsacus, and Constantinople expose the political and theological struggles over the Son’s substance and the Holy Spirit, while Julian’s apostasy brings renewed pagan pressure before Jovian and later Theodosius restore Christian privileges and Trinitarian orthodoxy. Theodosius convenes 150 bishops, confirms Nicaea, orders ecclesiastical discipline, and grants Constantinople second rank after Rome. The later narrative follows John Chrysostom’s reform of clergy, charitable work, opposition to simony and courtly abuses, conflict with Theophilus and Eudoxia, deposition at the Council of the Oak, exile, and death, with Pope Innocent I’s unsuccessful efforts to secure his restoration.