But let us make no mistake. The Elder will let no one off the hook who thinks that somehow, within the Christian, light and dark may safely and happily coexist. Light and darkness are opposites, and repel each other. One cannot have fellowship with God with one foot in darkness and one in light, since God is light; in him there is no darkness at all. One cannot serve God, who is light, while continuing to dwell in the realm that is hostile to or ignorant of God, which is the realm of darkness, for that is both to deny the very nature of God as pure light and to deny that God's character ought to shape ours as well.
Here it is crucial to take note of what the author does not say. "Darkness" is not simply equivalent to sin or wrongdoing. It is the realm that opposes and is hostile to God. This realm is characterized by disobe dience and lack of relationship to God. Thus John exhorts Christians— and all people—not to walk in darkness. But notice that he never says "Let there be no darkness in you," as if he were saying, "True Christians are without a trace of sin." Darkness is not a synonym for "indwelling sin." Darkness and light are not realities that are within each of us. Rather, they are realities greater than and external to us. Darkness and light are two opposing forces, each making their competing claims upon us. We are challenged to decide in which circle we will choose to live, and then we endeavor to live within it. This is to live by the truth.
There are many synonyms for the expression live by the truth: "does the will of God" (2:17), "do what pleases [God]" (3:22) and "does what is right" (2:29; 3:7; compare 3:10). Although the phrase aims at concrete moral and practical actions, it means more than "practicing what we preach." It means living in conformity with truth and light, living in accord with the character of God. Those whose allegiance is truly to God will be shaped by that commitment and by God's own character.
The result of committing oneself to God and to walk in the light is twofold. First, we have fellowship with one another. Those in the light are joined together in a fellowship whose primary guiding principle is Jesus' own command of mutual love (2:7-11). Second, those in this fellowship can be assured that the blood of Jesus, his Son, purifies us from every sin ("all sin"). In other words, those in the light do indeed sin— but they recognize the need to be purified from sin. On the other hand, those who claim they can walk in darkness deny the need for purifica tion. At first glance, this may strike us as an anomaly. Even though sin appears to belong in the realm of darkness, the continued intention to walk in the light and to shape one's life by God's own character will itself lead to a recognition of what is false and impure in us. We understand that impure actions or attitudes cannot simply be tolerated or ignored. We understand the implications of what it means that "God is light." But we also understand that we are not perfect light as God is. And yet we can also be confident that the blood or death of Jesus serves to wash away the impurity so that the believer may continue in fellowship with God (compare 1:3, 6; 2:3). And this acceptance of Jesus' death on our behalf is an ongoing part of our own walking in the light.
Fellowship with God is not mystical communion with a vague divine entity but a commitment to a righteous God, a commitment that in turn lays the demand upon us to walk in the light. Against the secessionists, then, the author asserts that not every experience which is claimed as an experience of God is in fact fellowship with God. Fellowship with God will always be characterized by walking in the light, doing the truth, living as God desires.
IVP New Testament Commentaries are made available by the generosity of InterVarsity Press.