Third-century Trinitarian heresy named for Sabellius, a Libyan presbyter active at Rome c. 215. Sabellianism teaches that Father, Son, and Holy Spirit are not three distinct Persons but three successive modes (Greek prosopa in the masks-of-actor sense, not in the substantive Person sense) or manifestations of the one God. The position is a form of modalist monarchianism (the broader category of heresies that protected the unity of God by reducing the three to one). The Sabellian formulation: there is one God who acts in three modes — as Father in creation and the OT economy, as Son in the incarnation and redemption, as Spirit in the present sanctifying work. The position is the substantive opposite of tritheism (which over-emphasizes the threeness at the expense of the unity); Sabellianism over-emphasizes the unity at the expense of the threeness. Both fail to maintain the orthodox confession of one God in three Persons. The heresy was condemned by multiple early councils and Fathers; Tertullian's Against Praxeas (early third century) is one of the principal early refutations (Praxeas was a related modalist whom Tertullian famously characterized as having put the Paraclete to flight and crucified the Father). The Reformed-confessional Trinitarian position (Westminster Confession II.3; Athanasian Creed) rejects Sabellianism as substantively heretical: the three Persons are eternally distinct (Father is not Son is not Spirit), eternally co-equal, eternally consubstantial (sharing one divine essence), and eternally related (the Father eternally generates the Son; the Spirit eternally proceeds from the Father, and from the Son in the Western filioque).