1 John

This is the eighteenth in a series of twenty-one summaries of the New Testament letters.  The eighteenth is 1 John, and the outline comes from Peter Leithart:

a   Concerning the word of life, 1:1-4
     b   Walking in light and love, 1:5-2:17
          c   Antichrists and the anointing, 2:18-29
               d   Loving the brethren; Jesus destroyed the devil, 2:28-3:24
          c'  Antichrists and the Spirit, 4:1-6
     b'  God is Love, 4:7-5:5
a'  Spirit, Water, Blood, 5:6-21

The 'a' pattern is linked by testimony.  In the first section, John testifies by what he has seen and touched.  In the second section, the Spirit, water, and blood all testify, and God too. (7-8) 

The 'b' pattern is linked by the theme of love.  In the first section, John says we should love one another: "Anyone who loves their brother and sister lives in the light, and there is nothing in them to make them stumble.  But anyone who hates a brother or sister is in the darkness and walks around in the darkness." (2:10-11)  In the second section, John describes love's origin in God: "we love because he first loved us." (4:19)

The 'c' pattern is linked by the theme of antichrist and false prophets.  In the first section, the liar is "whoever denies that Jesus is the Christ."  In the second section, John writes, "every spirit that acknowledges that Jesus Christ has come in the flesh is from God, but every spirit that does not acknowledge  Jesus is not from God." (4:2)

The central 'd' section, emphasizing love of Christ and love of neighbor: "And this is his command: to believe in the name of his Son, Jesus Christ, and to love one another as he commanded us." (3:23)