Cerinthus was a gnostic teacher in the last days of John the Apostle. Cerinthus taught that God did not create the world and he denied the divinity of Jesus. He taught that Jesus was a man who at His baptism was empowered by the "Christ" which guided Him in His earthly ministry. Then merfe moments before the death of Jesus on the cross, the "Christ" left Him leaving a mere mortal man to die. Cerinthus took mysticism and Christian doctrine and mixed them together in an attempt to destroy biblical doctrine. The heresies of Cerinthus can be detected in the teachings of Jehovah's Witnesses, Christian Science, and Mormonism.
Cerinthus was a contemporary of John the Baptist who wrote his first letter to churches in Asia that he was responsible for while living in Ephesus and his second letter to warn the less mature in their Christian faith and doctrine about the false teaching being circulated.
Tradition tells the story of the fervor of John's opposition to Cerinthus when John discovered Cerinthus in the same public bath house as John causing John to run out of the bath house yelling, "Let us fly, that the thermae (steam) fall not on our heads, since Cerinthus, the enemy of the truth, is therein."
The benefit and blessing of Cerinthus to the church was that it caused the early church to wrestle with and define the character and nature of Jesus Christ. It also resulted in John the Apostle defining the character of God as involved in the redemption of sinners. What a wonderful scheme of God to allow a heretic such as Cerinthus to rise up and challenge the teachings of Jesus in order to inspire John to write an epistle that clearly delineated God's plan of redemption.