I John 1: 5-10  John wants his readers to come and join in the fellowship that he enjoys with the Father and the Son and his brothers and sisters in Christ.  That fellowship starts with knowing the Truth.. the Word of Life..  

The first thing that we must know and believe and accept is this.. "God is light and in Him there is no darkness at all."  Light shines. It makes it possible to see. Without it we cannot live. Darkness obscures. It hides everything. In darkness.. we cannot see.  We understand this on a physical level.  We need to understand it more clearly on a spiritual level. 

From the beginning of creation God has "separated" or made a distinction between light and darkness. (Genesis 1: 4 "And God saw that the light was good; and God separated the light from the darkness."  And, we know that in the end.. in eternity that there will be no more darkness.. "And the city has no need of the sun or the moon to shine upon it, for the glory of God has illuminated it, and its lamp is the Lamb." (Revelation 21:23) 

Jesus said, "I am the light of the world; he who follows Me shall not walk in darkness but shall have the light of life." ( John 8:12)  Later he said, "For a little while longer the light is among you. Walk while you have the light, that darkness may not overtake you; he who walks in the darkness does not know where he goes. While you have the light, believe in the light in order that you may become sons of light." (John 12:35-36)

John is emphasizing  this distinction between darkness and light.  "If we say we have fellowship with Him and yet walk in the darkness, we lie and do not practice the truth;"  True fellowship, partnership, and participation with the King who is Light.. cannot co-exist..  participate, partner, or fellowship with darkness.

Light manifests.. darkness hides.  Jesus calls us to walk "in the light as He Himself is in the light."  We can only do that by the power of His blood that "cleanses us from all sins." 

We can only be in the light when we let His Word shine in our hearts, to uncover that which is hidden.. 

We must acknowledge the hidden sins... no longer "deceiving ourselves" by thinking we have no sin. 

We must "confess our sins."

We must trust in Jesus who is "faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness."

There were two false doctrines that John was addressing here.  The first "antinomianism" believed that because of the covenant of grace, which is unconditional, man could not be held accountable to the moral law.  He just had to believe and he was justified and then nothing else mattered.  The second belief was "perfectionism". The belief was that the sin nature was completely eradicated.  John is making it clear in this letter that neither of these ideas were true.  We still have a choice in the way we live our lives. And we must choose.. We can choose light or darkness.  But we cannot choose both. We will be accountable before our Lord for the choices we make. 

Father in heaven, You are Light and there is no darkness in You at all. We desire to walk in the Light and to reflect the light of our Savior, Jesus Christ.  Shine Your light into our hearts and uncover any hidden sins, that we might confess our sins and find forgiveness in our faithful Savior. Thank You for giving us the Light of the World. Spirit of God, may Your power at work in us sanctify us through and through, so that the Light of Jesus will shine forth in our lives. We ask this in His Holy Name. Amen.