In our own day, modalism and Arianism have reappeared in the teaching of Oneness Pentecostalism and the teaching of Jehovah’s Witnesses, respectively. Modalism finds advocates in Oneness Pentecostals, as is evident from the name of the movement. Oneness Pentecostals believe that there is only one divine person and that the doctrine of the Trinity is unbiblical. They believe that Jesus is the only person in the Godhead. Jesus exists in two modes: as the Father in the heavens and then, subsequently, as Jesus the Son on earth. The Holy Spirit is not a person but only a manifestation of the power of Jesus.
Jehovah’s Witnesses in many respects sound Christian and even profess to worship Jesus. But like the Arians of the early church, they believe Jesus is a mere creature and not equally and eternally God. Jesus is the firstborn over all the creation, but He is not Light of Light and very God of very God—that is, God in the flesh. Jehovah’s Witnesses, therefore, reject the doctrine of the Trinity as well as the full deity of the Son.
In recent years, semi-Arian teachings have arguably made a comeback as a number of high-profile evangelical theologians have argued for the eternal subordination of the Son (ESS). Advocates of ESS project the redemptive and voluntary submission of the Son in history back into eternity and argue that the Son eternally submits to the Father and is thus eternally subordinate to Him. Such claims sound eerily similar to semi-Arian claims that the Son is of like substance with the Father but not fully divine or of the exact same substance and thus fully equal with the Father. Unlike historical semi-Arians, modern proponents of ESS affirm that the Son is of the same essence (homoousios) as the Father. However, by positing different levels of authority and submission in the Godhead, they undermine their affirmation. That is because divine authority is a property of the divine essence, which means that different levels of authority ultimately suggest that the Son has a different—and lesser—divine essence than the Father. While not every advocate of ESS necessarily promotes the eternal subordination of the Son in the same way, and though these advocates are not necessarily trying to deny the equality of essence between the Father and the Son, they nevertheless flirt with heresy when they say that the Son is eternally submissive to the Father.
Needless to say, the church must always be vigilant in guarding against heretical teaching. True, many Christians unknowingly advocate doctrinal errors because they misunderstand the Bible. Errors can mark our doctrine, but when God teaches us the truth, we gladly set aside our mistaken beliefs. Heresy, on the other hand, is when a person knowingly rejects a central tenet of the Christian faith, typically indexed by the doctrines enumerated in the Nicene Creed—the doctrine of God, the Trinity, or Christ, for example. Make no mistake: modalism, Arianism, and semi-Arianism are heresies. The church must always be on guard against them and must always be prepared both to teach the truth of Scripture and to reclaim heretical brothers and sisters through church discipline.