Researched by the Ignaria Editorial Team · Published 2026-04-19
Nicaea (325 AD) declared the Son homoousios — "of the same substance" — with the Father, but it left the theological framework underdeveloped. The Arian controversy continued for decades because the vocabulary to articulate three divine persons without tritheism had not yet been established. The Cappadocian Fathers — Basil of Caesarea, his brother Gregory of Nyssa, and their friend Gregory of Nazianzus — supplied that vocabulary. They distinguished hypostasis (individual subsistence) from ousia (shared essence), allowing the Church to confess one God in three persons without contradiction. Their framework made the Council of Constantinople (381 AD) possible, producing the Niceno-Constantinopolitan Creed that is still used across Eastern and Western Christianity.
What the primary sources show
Basil grounds the Spirit's divinity in Scripture and tradition, extending Nicene Trinitarianism to include the third person. His careful terminological work on hypostasis and ousia gave the Church the grammar for orthodox Trinitarian confession.
Gregory of Nyssa systematically refutes the Anomoean Eunomius — who argued the Son is utterly unlike the Father — by showing that "ungenerate" describes God's mode of existing, not a superior essence. His argument preserves full Trinitarian equality.