The epistles of John show Jesus as the way, the truth and the life. 1 John was written for several reasons, that our joy might be complete, that we would not sin, that we would guard against false teachers and that we would know that we have eternal life by believing in the name of the Son of God.
The word know is used more than thirty times in this short letter – John is being emphatic about this wonderful truth of life in His name. He starts off his epistle by saying that Jesus has walked among them and he has touched this Life. John wants us to walk in this life and to walk in it is to walk in the life and while you walk in light darkness is exposed. When darkness is exposed we can claim the blood of Jesus , for this is our sanctification, to walk with Him, to learn and be changed by Him.