John is especially concerned that his audience, which has been battered by false teaching, walks in truth and light.  Whereas many assume that this is all about obedience to the Law, John clarifies that this is, first and foremost, about confessing one's sins in faith and receiving the blessing of forgiveness.  The wonderful news is that God has bound Himself to His people and, as truly as He is faithful and just, He will forgive their sins.