"This is the message we have heard from him and proclaim to you, that God is light and in him is no darkness at all. If we say we have fellowship with him while we walk in darkness, we lie and do not live according to the truth" (1 John 1:5-6).
The author begins with the image of God as light in whom there is no shadow. If we try to balance our lives between shadow and light, we cannot. We are either in the light or not. What keeps us out of the light is sin, which we understand to mean actions that arise from error thought. We cannot live our lives in shadow and claim to be one with our Source. As eternal spiritual beings we are always one with Source, of course, but we cannot claim that relationship without surrendering fully to the light that is God.