Modalistic Monarchianism (also known as modalism or 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.
Theologian and church historian Adolf von Harnack first used the term modalism to describe a doctrine believed in the late 2nd century and 3rd century. During this time period, Christian theologians were attempting to clarify the relationship between God the Father, the Son and the Holy Spirit. Concerned with defending the absolute unity of God, modalists such as Noetus, Praxeas and Sabellius explained the divinity of Jesus Christ and the Holy Spirit as the one God revealing himself in different ways or modes:
Modalistic Monarchianism is accepted within Oneness Pentecostalism. Oneness Pentecostals 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. They also believe that, 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, Oneness Pentecostals 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), they 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.
The theology of the World Mission Society Church of God and its youth representing group ASEZ is another example of modalism.[original research?] They believe that, "'God' coherently refers to God the Father throughout the Bible. Apostle Paul, the writer of Philippians and Romans, testified that God the Son Jesus is in very nature God, indicating that He is God the Father Jehovah, who was born in the flesh." They believe that, later on, the Holy Spirit came on the human form to be revealed as Ahnsahnghong, who they believe is God the son of Jesus Christ: "In accordance with the Bible, God the Holy Spirit must also have a name. The name of the Holy Spirit is Ahnsahnghong. Ahnsahnghong is the Holy Spirit because He fulfilled the prophecy of the one to come and remind us of the truth Jesus taught. So God the Holy Spirit Ahnsahnghong is God the Son Jesus Christ."