The point at which a movement usually moves from orthodoxy to heresy is its understanding of Jesus. If we get Jesus wrong, we get everything wrong.
1. Jesus is not a created being. The Arian heresy (similar to the Jehovah’s Witnesses) almost took over the Church. The reason the Nicene Council was called was to clarify the Son’s nature and they concluded that the Son was not created. Before there was Jesus of Nazareth, there was God the Son.
2. There really was a historical Jesus. Despite what Jesus mythicists claim, Jesus is not a symbol, image or myth. Jesus is as historical as any other ancient figure and the evidence we have is very good.
3. Jesus was born of a virgin. The virgin birth (more accurately the virginal conception) is not an attempt to copy pagan virgin births (it is actually hard to find a pagan virgin birth). It is difficult to make sense of the incarnation if Jesus’ human existence is fully explainable by the actions of a man and a woman.
4. The incarnation must be taken seriously. Jesus was not God pretending to be a man. Jesus was as fully man as he was fully God. He had to learn to walk and talk as every human child must. He got tired and hungry as all normal people do.
5. Jesus died for our sins. The death of Jesus was not just the wrongful death of an innocent man. Jesus could have prevented his death by keeping away from Jerusalem. Jesus had to die to bridge the gap between God and humanity, thus reconciling us through the redemption of sin.
6. Jesus was resurrected. The resurrection is not a pleasant epilogue to make the story end on a positive note. The resurrection is essential to the story. Evidence from Acts and Paul’s letters suggests that the resurrection was often preached more than the crucifixion. It is the resurrection that demonstrates the truth of all that Jesus said and did.
7. Jesus will come again. The second coming is not the invention of some religious fanatics. It is found throughout the New Testament. Jesus fulfilled some Old Testament prophecies but there are promises of restoration that have not been fulfilled. The Day of the Lord is coming when all things will be made right. That will happen when Jesus returns and the general resurrection takes place.
Is a group that you encounter orthodox or heretical? This list of essential beliefs about Jesus is a good test.