John's letters have several comparing and contrasting ideas to help his readers understand and evaluate if they are walking in....

light or darkness

love or hatred

truth or falsehood

John says that either we confess Jesus as the Son of God who has come in the flesh, or we follow those who are anti-Christ. We cannot believe or support both.

John’s letters bring together powerfully the three aspects of authentic Christian living: true doctrine (mind), selfless love (heart), and obedient action (will).