If God so loved as John has described in 1 John 4:7-10, then the only possible response is to love one another (4:11-12). This is a conditional sentence that assumes the premise is true, something like “since God has loved us by sending his son, then we ought to love one another.”
The only way the world will see God is through behavior of his people. When we demonstrate our love for God by loving one another, we reveal God to the world.
This is challenging since the world does not usually associate love with the organized church. Whether this is the classic cranky nun teaching in a Catholic school or an abusive priest, the puritanical Baptist pastor ranting against sin, preaching hellfire and brimstone on the street corner; the gossiping old women judging the way a younger woman is dressed in church; judging the kid with tattoos and piercings and wearing his ball cap in the church (backwards of course).
The Holy Spirit is evidence we are abiding in God (4:13). Once again John states we “abide in him” and God “abides in us.” Does this plural pronoun mean, God abides in me as an individual, or God abides in the community of believers? This is ambiguous, and it is (perhaps intentionally) unclear whether John intended the reader as an individual to imagine God’s love abiding in them personally or whether John is describing how a local church ought to function as a living community.
Gift of the Holy Spirit promised in John 15. The Holy Spirit is also called the “Spirit of Truth” in the Gospel of John 14:17 and 16:13. Here in 1 John 4:6 (cf. 5:6) John describes the role of the Spirit of God as enabling the believer to discern true teaching from false. In Second Temple Period Judaism, the “spirit of truth” has a similar use of the phrase.
How does the presence and activity of the Holy Spirit express itself in love for one another? In the letter John has already stated Jesus is the messiah and son of God sent in the flesh, Now John expands is view of Jesus to include “savior of the world” (4:14-15).
Would the opponents deny this? It is easy enough to believe a Jewish teacher named Jesus lived in Galilee and gathered some disciples, challenged Jewish Temple aristocracy and was falsely accused as attacking the Roman government, resulting in his crucifixion. But is this knowledge of a historical Jesus enough to be “born of God”? For John, Jesus is the Messiah, the Son of God revealed in the flesh, and the Savior of the world. These are not theological points people can pick one or two of and be born of God. This is a full package, all are required to “abide in God.”
It is remarkable Jesus is the savior of the world since in John’s Gospel the world is in active rebellion against God. Yet John 3:16 says God loved the world and sent his son to be an atoning sacrifice for the world. That Jesus “saved the world” is another gracious act in which God extends salvation to people who are in total rebellion against him, unable and unwilling to do anything to reconcile themselves to God.