The contrast of light and dark is one of the most basic concepts in our realm of understanding. Where there is light, there cannot be darkness, and vice versa. Light is good – from it comes warmth, life, and clarity; and darkness is just the opposite. These are things we grasp naturally from an early age. And, not only in this letter but in all of his writings, John uses these common terms to convey to us the most profound enlightenments. He conveys to us, that is, the very character of God and His contrast to sin.
One of my favorite verses in Scripture is in the introduction of John's gospel account. He refers to Jesus as “the light of man,” and then goes on to say, “The light shines into the darkness and the darkness just can't handle it.” Darkness itself never overtakes light, but the very existence of light dissipates darkness by nature. God is by nature righteousness itself, He is light and therefore leaves no room for sin, no place for darkness, in His way. It is such a stark contrast, an extreme separation of two entities, but isn't great to have such clarity? And we know this deep within our own spirit just as firmly and naturally as we know the character of light. God is not a politician, smiling and saying all the right things while doing something else entirely. He doesn't have a closet of skeletons to hide, and He's not pulling a fast one over on us. He is simply good, and there is no evil in Him, no sin, no darkness at all.