The apostle John primarily writes about two topics in these passages. The first is primarily on faith and how it is interconnected with love. To have real faith, you will love God and love others. And to have real love for God, you will follow His commandments. And the second has to deal with the testimony and witness for the truthfulness of the Gospel of Jesus Christ. Namely that God Himself has testified to it, and as a result, if we reject His testimony, we call Him a liar.
