I identified sixth themes in this letter from the apostle John: (1) Love is the essence of Christianity; (2) deeds matter, and we all sin; (3) Christ was physically real and the Son of God; (4) belief in Him is central to salvation; (5) there exists evil and it can be identified; and (6) we live in a fallen world. These themes of course overlap.
Let me elaborate on each, giving chapter and verse (literally):
- Love is central to Christianity. Indeed, it is stated twice that “God is love.” 4:8, 16. Love’s importance is elaborated on at 2:9-11; 3:11-18, 23; and 4:7-21. Cf. 1:5 (“God is light”); some commentators summarize the message of this letter as God is light, God is love, and God is life.
- Deeds matter. See 1:6; 2:1-7, 29; 3:4-12, 18, 24; 5:2-3. We all sin, but we can be redeemed. 1:7-10.
- Christ is physically real and is the Son of God. 1:1, 3; 5:5.
- Belief in Christ is central to salvation (echoing John 3:16). See chapter 5 generally (e.g., 5:13); see also 3:23; and 4:13-15; cf. 2:25.
- There exists evil and it can be identified. Note explicit references to “the evil one” (3:12, 5:18-19) and “the devil” (3:8, 10). There’s also reference to “the antichrist” (2:22, 4:3). There are multiple spirits and there are false prophets, so, to tell the good from the bad, John says one that “confesses that Jesus Christ has come in the flesh is from God” (4:2); see also 2:22-26.
- We live in a fallen world. Abruptly, John warns, “Do not marvel, brethren, if the world hates you.” See also 2:18 (“Children, it is the last hour”); cf. 2:15.
The stress on deeds mattering and the physicality of Christ was apparently aimed at Gnostic/Docetist heresies.
Finally, I was struck by the final verse (5:21): “Little children, guard yourselves from idols.” It’s not surprising, of course, to be told that Christians are not to worship idols, but there’s no connection in this letter between this injunction and anything else: It just appears abruptly and at the very end. Some commentators suggest that in this context we should read “idols” more broadly than just those little figurines: It can be anything that stands between the believer and right belief.