Contrast brings clarity

1:9 If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness.

3:20 If our hearts condemn us, we know that God is greater than our hearts, and he knows everything.

4:4 You, dear children, are from God and have overcome them, because the one who is in you is greater than the one who is in the world.

4:16 God is love

5:13 I write these things to you who believe in the name of the Son of God so that you may know that you have eternal life.

2:4 Whoever says, “I know him,” but does not do what he commands is a liar, and the truth is not in that person.

2:15 Do not love the world or anything in the world. If anyone loves the world, love for the Father is not in them. 16 For everything in the world—the lust of the flesh, the lust of the eyes, and the pride of life—comes not from the Father but from the world.

3:6 No one who lives in him keeps on sinning. No one who continues to sin has either seen him or known him.

3:8 The one who does what is sinful is of the devil, because the devil has been sinning from the beginning.

4:3 but every spirit that does not acknowledge Jesus is not from God. This is the spirit of the antichrist, which you have heard is coming and even now is already in the world.

Exegesis vs. Eisegesis

Main themes

To make our joy "full" or complete (1:4)

To warn us about habitual sin (2:1)

To refute false teachers (2:26)

To assure us of our salvation (5:13)