The true identity of Jesus of Nazareth is at the heart of the problem with both Christians and non-Christians. Many people who identify as evangelical Christians don’t believe Jesus is the Eternal God. They believe Jesus was God’s first created being and that God assigned Jesus to create the universe. They view Jesus as powerful and necessary for salvation, but don’t believe He is God. Non-Christians, of course, don’t believe Jesus is God.
John the Apostle taught that Jesus is the Word of God and came to earth in flesh:
In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God … And the Word became flesh and dwelt among us, and we beheld His glory, the glory as of the only begotten of the Father, full of grace and truth. John 1:1-2, 14
John wrote that whether people believe Jesus is God in the flesh is how we know if they are real Christians or not:
Beloved, do not believe every spirit, but test the spirits, whether they are of God; because many false prophets have gone out into the world. By this you know the Spirit of God: Every spirit that confesses that Jesus Christ has come in the flesh is of God, and every spirit that does not confess that Jesus Christ has come in the flesh is not of God. And this is the spirit of the Antichrist, which you have heard was coming, and is now already in the world. 1 John 4:1-3
John was right. That is the spirit of Antichrist that is still in the world today. The issue of whether Jesus is Eternal God come in flesh has been a sticking point since the early days of Christianity. You may find it helpful to read a lengthy series we published several years ago titled “A Reading Plan for Christian Apologists.” The series is available in 32 individual posts from 2016-2018 or in three eBooks published in 2018. As you read through the writings of the Apostolic and Church Fathers, you will find many apologetics responses to people who denied that Jesus was God in the flesh. The early Christian Apologists called those people “heretics” because what they believed and taught was heresy (a teaching contrary to Scripture).