An explanation

I John 4:2 “This is how you can recognize the Spirit of God:  Every spirit that acknowledges that Jesus Christ has come in the flesh is from God.” John wants to tell us what true doctrine is.  He gives each of us an easy test to decipher truth from error.  Does the person or religious belief believe Jesus, God, came to this earth and became a human man?  Simple question with a yes or no answer and the answer determines truth.  Other truth facts follow, but this basic truth is the foundation of true faith.