d. iv. 1-v. 12. The Sources of Sonship: Possession of the Spirit as shown by Confession of the Incarnation.
- The Spirit of Truth and the Spirit of Error (iv. 1-6)
- Love is the Mark of the Children of Him who is Love (iv. 7-21).
- Faith Is the Source of Love, the Victory over the World, and the Possession of Life (v. 1-12)

In this chapter true faith is described as acknowledging the Messiahship of Jesus, as experiencing the new birth, as aflame with love to God and to all the regenerate, as keeping God's commands, as victorious over the world, as having inward self-attestation and eternal life, and as having boldness and success in prayer. The apostle in iv. 12 details the various evidences on which the Christian faith rests, and declares faith and love to be inseparable, that alike worthless is a faith which does not inspire love, and a love not the offspring of faith. The transition from the former chapter lies in the idea of brotherhood, not human, but Christian, arising from a love flowing from a vital apprehension of Christ as both an almighty Saviour and a supreme Lord. On the plane of love inspired by the Holy Spirit, this brotherhood is not an arbitrary command, but a natural outflow from this diffusive principle.