Stay Content with what the Apostles Taught

II John 9-11 "Anyone who runs ahead and does not continue in the teaching of Christ does not have God; whoever continues in the teaching has both the Father and the Son. If anyone comes to you and does not bring this teaching, do not take him into your house or welcome him. Anyone who welcomes him shares in his wicked work."
 
This is one of the strongest worded statements in scripture about how we react to false teachers.  But I want to draw attention to the structure of the admonition as John addresses the full range of reaction to the doctrine of Christ.
 
John first mentions those who go too far; they add their own speculation or teachings to the existing doctrine of Christ.  These do not have God.  Then he mentions those who abide in the teaching.  They are content with what the apostles taught; they have fellowship with the Father and the Son.  Finally, he mentions those who fail to teach the truth about Christ.  Their error is not so much what they say; it is what they will not say. 
 
Seeing how important this was to John, we need to understand the doctrine of Christ and then be ready to react as we come into contact with those who refuse to abide in the same.