1 John 5:19

We know that we are children of God, and that the whole world is under the control of the evil one.

(v19, NIV)

John's audience is a certain group of people. These people are true believers and followers of the Lord Jesus Christ. According to the tests and proofs shown in this letter, they may know that they have eternal life. His readers should know that they are in fact children of God. Further inspection of these proofs or tests also reveals the opposite of their intended purpose. Not only does it confirm believers of their salvation, but it would hopefully reveal to non-believers their true condition. The current state and condition of all these people who are without God speaks of how lost and hopeless we are without God. It also shows us of the control and hold the evil one has on this world. Yet, as children of God, do not be afraid. Know that you are children of God, if in fact you are. That seems redundant or somewhat odd, but examine yourself to find out.