This letter of First John teaches us that, while we live in the world, Satan's army continually assaults the Church with false teaching, exacerbating the struggle of life, making us feel overwhelmed by sin, brokenness, doubts, and fears of death.  But this letter is also filled with hope and instruction - we have already overcome the world by faith, which comes from the new birth.  We have also begun to bring forth the fruit of our victory, loving God and our brothers and sisters. But what is it that must be believed?  The gospel message of Jesus Christ - being the incarnate Son of God, He came to bring us eternal life, through both His baptism (water) and His death (blood).  Today, this message of eternal life is declared by the Holy Spirit in preaching (cf. 1 Jn. 4:1-6), by the water in Baptism, and by the blood in the Supper.  Though we endure affliction on earth, we trust that our victory is secured.