Modalistic Monarchianism (also known as Oneness Christology) is a Christian theology that upholds the oneness of God as well as the deity of Jesus Christ. It is a form of Monarchianism and as such stands in contrast with Trinitarianism. Modalistic Monarchianism considers God to be one while working through the different "modes" or "manifestations" of Father, Son, and Holy Spirit. Following this view, all the Godhead is understood to have dwelt in Jesus Christ from the incarnation. The terms Father and Son are then used to describe the distinction between the transcendence of God and the incarnation (God in immanence). Lastly, since God is a spirit, it is held that the Holy Spirit should not be understood as a separate entity but rather to describe God in action.
Modalistic Monarchians believe in the deity of Jesus and understand Jesus to be a manifestation of Yahweh, the God of the Old Testament, in the flesh. For this reason they find it suitable to ascribe all worship appropriate to God alone to Jesus also.
Being Judean, the first Christians held to the Israelite Shema and prayed to Yahweh as God alone. However, after the resurrection of Jesus there was a shift, and the early church came to understand and worship Jesus as God. As a result, though their language seems fluid, there was a distinction made in their language between God in transcendence and the man Jesus. This apparent dissonance led to the creation of various models to resolve the relationship between the two. Monarchians seek to explain this relationship without causing a division within God. Writing against Praxeas (a Modalistic Monarchian) in the third century, Tertullian gave evidence that the majority of Christians were Monarchian when he noted their startled reaction to his teaching of God as three in one. Other notable adherents in early Christianity include Noetus and Sabellius (see Sabellianism). However, their writings were destroyed so their views are only known from their opponents.
Monarchians were opposed by Logos theologians (Tertullian, Hippolytus, Clement of Alexandria, and Origen of Alexandria), who believed Jesus to be only the incarnation of a preexistent Logos, rather than the incarnation of God in his fullness. Though much debate occurred, gradually all Monarchians became silenced, and the Trinitarian view gained prominence being adopted in the First Council of Constantinople. After this, Modalistic Monarchianism was labeled as a heresy under the name of Sabellianism.
Modalistic Monarchians believe in the deity of Jesus and understand Jesus, the Son of God, to be a manifestation of the God of the Old Testament, Yahweh, in the flesh. When Jesus was on Earth, he referred to God as his Father since God caused his conception through the Holy Spirit. Since God is spirit, the Holy Spirit is used to describe God in action. In this way, Father, Son, and Holy Spirit are considered titles pertaining to the one God, not descriptions of distinct individuals.
Because Father, Son, and Holy Spirit are maintained to be titles, most Modalistic Monarchians would believe that they fulfill the commandment of Jesus in Matthew 28:19 to baptize in the name of the Father, Son, and Holy Spirit by baptizing solely in the name of Jesus Christ. Because Jesus is the name given for salvation (Acts 4:12), Modalistic Monarchians would argue that this led the Apostles in the book of Acts fulfilling the commandment of Jesus by baptizing in the one name of the one God, Jesus.
Much of their theology attempts to begin with an Old Testament understanding of God in order to understand what the first Apostles would have believed about Jesus. They also seek to avoid use of theological categories produced by Platonic-Aristotelian epistemologies, preferring rather to tell the story of redemption through narrative. Thus, the distinction found in the New Testament writers between God the Father and Jesus is understood to be from the attempts to identify God the Father and Jesus together, rather than to separate them more than necessary.