- Arianism’s resurgence
- The Cappadocian Fathers
- Basil the Great
- Gregory of Nazianzus
- Gregory of Nyssa
- The Council of Constantinople (381 AD) – the second ecumenical council
- The three worlds of Christendom by the end of the fourth century:
- Greek-speaking East of the Roman Empire
- Latin-speaking West of the Roman Empire
- Aramaic-speaking churches of East Syria & beyond