If we abide in the doctrine of Christ, we have both the Father and the Son  -  2 John 9

Whosoever transgresseth, and abideth not in the doctrine of Christ, hath not God. He that abideth in the doctrine of Christ, he hath both the Father and the Son.

John focused on the characteristics of false teachers. They claim to have a new revelation, teach doctrines that God has not revealed in His Word, and refuse to believe the doctrine of Christ. Though they claim to know God, they do not believe in the absolute deity and humanity of Christ, which reveals that they do not know nor have God at all.