Sabellianism

The heresy of Sabellianism was an early form of theological modalism, which is the belief that the Father, Son and Holy Spirit are three different modes of God, as opposed to the Trinitarian view of three distinct persons within the Godhead.  The term Sabellianism comes from Sabellius, who was a theologian and priest from the 3rd century. None of his writings have survived and so all that is known about him comes from his opponents, who purport that Sabellius taught that God was single and indivisible, with Father, Son, and Holy Spirit being three modes or manifestations of one divine Person.  This teaching had come to him from the teachings of Noetus, who was excommunicated from the Church.  Hippolytus of Rome knew Sabellius personally and admonished Sabellius in his work ‘Refutation of All Heresies’ for furthering the “heresy of Noetus”.

Since the distinction between ousia (substance) and hypostasis (person) was not worked out until the late fourth century, at the Councils of Nicaea, Ephesus, and Chalcedon, Sabellius used the word person in a different sense; one that would be understood in later centuries as being more synonymous with “nature” (physis).  Despite this distinction, Sabellius held an unorthodox view that the One God successively revealed Himself to man throughout time as the Father in Creation; the Son in Redemption; and the Spirit in Sanctification and Regeneration as opposed to Trinitarianism, which was eventually defined as three distinct, co-equal, co-eternal persons of one substance. The Greek term homoousian or (ὁμοούσιος) meaning “consubstantial” would later be adopted at the First Council of Nicaea to describe the relationship between the three distinct persons (prosopon) of the God-head being of the same divine substance.  It has been noted that this Greek term homoousian (‘same being’ or ‘consubstantial’), was also a term reportedly used by Sabellius, who also considered the Father and the Son to be “one substance”.  However, to  Sabellius, the Father and Son were one essential person, operating as different manifestations or modes. Athanasius of Alexandria on the other hand, used the word to affirm that while the Father and Son are eternally distinct persons, both are nevertheless one divine essence, nature, or substance.

Source:  Jaroslav Pelikan, The Emergence of the Catholic Tradition (100-600), The University of Chicago Press, 1975