Another inadequate view of God, modalism, is the basic belief that God is one in both nature and person. Thus, the Father, the Son, and the Holy Spirit are not believed to be distinct from one another. One early form of modalism (called Sabellianism and popularized by the third- century theologian, Sabellius) taught that the one God first revealed Himself as Father in creation and in His relationship to Israel. He then revealed Himself as the Son during the life of Jesus Christ for the purpose of redemption. Finally, after Jesus’ ascent to heaven, He reveals Himself as the Holy Spirit in the life of the church.
According to Sabellius, God is Father, Son, and Holy Spirit successively but not simultaneously. Modalism can also refer to the belief that God presently manifests Himself to us sometimes as Father, sometimes as Son, and sometimes as Holy Spirit. All forms of modalism maintain that there are no real personal distinctions between Father, Son, and Holy Spirit.
Some movements today still embrace various forms of modalism. Oneness Pentecostals and all forms of Unitarianism are modalistic in their theology. Further, some Christians who consciously affirm orthodox Christian belief systems might inadvertently hold to a kind of modalism if not instructed concerning the Bible’s teaching about the triune identity of God.
Tri-theism refers to the belief that the Father, the Son, and the Holy Spirit are each equal as God, though not one in being. In other words, three separate beings are God. Thus, there are three separate beings are God. Thus, there are three Gods. This, of course, denies the clear biblical teaching that there is only one true and living God (Deut 6:4; Rom 3:30). The charge of tri-theism is often leveled against Christians by the strictly monotheistic Jews and Muslims. Early Christians sought to avoid this charge by teaching that God is one in substance or essence (Gk, ousia) and three in person (Gk hypostasis). Today contemporary theologians engaging in the articulation of Trinitarian theology must be careful to articulate the oneness of God in a way that faithfully maintains the fundamental biblical truth that God truly is one.