Heresy is false teaching that strikes at the essential truths of Christianity, and we are warned throughout Scripture that heretics will attempt to lead God’s people astray (Deut. 13:1–5; Acts 20:29–31). The history of Christian theology is in many ways the history of heresies, for many of the creedal summaries of biblical teaching were produced as a result of the church’s having to battle heresy and to define the boundaries of the truth. Christological heresies came in many forms in the early church, but many of them held in common a denial of the true deity of Christ.
One of the earliest Christian heresies was proclaimed by a group known as the Ebionites. The Ebionites were members of a Jewish sect that believed Jesus was the Messiah, but according to their understanding, the Messiah was merely a man. He was a great man, even the greatest possible man, anointed by the Spirit of God for the messianic office. Nevertheless, He was only a man, possessing only a human nature. The Ebionites found “support” for their position in texts such as Mark 1:9–11, which describes the anointing of Jesus with the Holy Spirit at His baptism. When this passage is read in light of the entire biblical witness, however, it is clear that while Jesus was a man, He was also far more than a man. The Ebionites did not pose a threat to Christian orthodoxy for long, as they died out by about the fifth century.
Arianism was the second major heresy from the early church that denied the true deity of Christ. Unlike the Ebionites, the Arians believed that the Son of God existed before the birth of Jesus and, in fact, before the creation of the universe. Yet, the Arians denied that the Son is uncreated. Arianism taught that the Son is the first and greatest creation of the Father, so the Arians exalted the Son over every other creature. Still, because the Son is a created being, He is not truly divine. As exalted as He is, He is still inferior to God. The church condemned Arianism at the Council of Nicaea in 325, but Arian notions have popped up repeatedly throughout church history.
The Council of Nicaea affirmed the full deity of Christ, saying that He has the same essence as the Father, but this was worked out only after much debate. Before Nicaea, the mainstream of the church did confess that Jesus is divine, though many thinkers did not articulate the deity of Christ in the most helpful way. Still, there was broad recognition that Jesus could not be merely human and save people from sin.