I’ve commented before on the sequence of 1 John 1:7, which moves from walking in the light to fellowship with one another, to cleansing by Jesus’ blood. The presence of “fellowship with one another” between walking in the light and cleansing is striking. Equally striking is the conditional introduction to the entire verse. Our ability to have fellowship with one another depends on our walking in the light; that makes sense, light and darkness are incompatible with one another, and to walk together in and as light we must all be walking in light. But John is also saying that walking in the light is a condition for being cleansed by the blood of Jesus:
“If we walk in the light . . . . the blood of Jesus cleanses us from all sin.” Suppose we don’t walk in the light, what then? It appears that we are not cleansed.
And what does it mean to walk in light? Well, John’s initial claim is that “God is light” (1:5), and that means that we have to walk “in God” in some way to receive the cleansing of Jesus’ blood. More concretely, walking in the light means walking “in the same manner as He walked” (2:6) and loving the brothers (2:9-11). Walking in love thus appears to be a condition for being cleansed of sin. Does John contradict Paul? Of course not, no more than James contradicts Paul. Walking in the light definitely means trusting in God and His Word; to disbelieve God is to call God a liar, and John has some choice things to say about that (1:9-10).