1 Jn 1.5 Now this is the gospel message we have heard from him and announce to you: God is light, and in him there is no darkness at all. ⁶ If we say we have fellowship with him and yet keep on walking in the darkness, we are lying and not practicing the truth. ⁷ But if we walk in the light as he himself is in the light, we have fellowship with one another and the blood of Jesus his Son cleanses us from all sin. ⁸ If we say we do not bear the guilt of sin, we are deceiving ourselves and the truth is not in us. ⁹ But if we confess our sins, he is faithful and righteous, forgiving us our sins and cleansing us from all unrighteousness. ¹⁰ If we say we have not sinned, we make him a liar and his word is not in us.

What does it mean to say that “God is completely light”?

The Greek is ὁ θεὸς φῶς ἐστιν καὶ σκοτία ἐν αὐτῷ οὐκ ἔστιν οὐδεμία, “God is light and darkness is not in him not one bit,” or something like that.  It’s emphatic; there is NO darkness in God.

I find it very interesting that John immediately follows this description of God–completely light, no darkness at all–with a description of how our own “walking in light” involves not perfection but confession, repentance.

In other words, there is no pretense that we, even as we walk in the light, are sinless.  Instead, we are told to keep on confessing.  (In v. 9, the present active participle ὁμολογῶμεν emphasizes that this confession of sins is an ongoing, habitual, characteristic thing, not a one-time action.)

Walking in the light is not moral perfection.  Walking in the light is following Jesus, even when it is a struggle, with absolute honesty about those struggles.

Who are we trying to fool?  We can’t fool God.  We shouldn’t try to fool one another.  Most dangerous is when we try to fool ourselves, “I am better than that other person, I am more deserving, …”

God knows.  When we claim to be better we deceive ourselves (v. 8).  Only by walking in confession and repentance do we walk in the light (περιπατῶμεν in v. 7, which is also a present participle emphasizing ongoing, habitual, characteristic action.)