second half of the 4th century

The Cappadocians: "one ousia and three hypostases" and the charge of tritheism

Basil the Great, Gregory of Nazianzus and Gregory of Nyssa – a young Nicene party of disciples of Origen – distinguished terms that in philosophy and even in the decisions of Nicaea had been used as synonyms: "ousia" is the substance common to all Three, "hypostasis" the individual existence of each. Lane sees in this a synthesis of the Nicene homoousios with Origen's assertion of three hypostases. The hypostases differ only by origin: the Father is unbegotten, the Son begotten, the Spirit proceeds; the Cappadocians found the guarantee of unity in the Father as the single cause. The comparison with three men sharing one humanity provoked the charge of tritheism; Gregory of Nyssa replied with the treatise On "Not Three Gods", pointing out that the actions of the three Persons are always common.