What does 1 John 1:5 mean?

This verse begins the main body of the letter which focuses on "walking in the light." This theme continues through the end of the chapter in verse 10. Echoing his words in verse 3, John notes that he is speaking of first-hand information. The use of "we" likely refers to John and the other apostles. They heard directly from Jesus and then proclaimed—or announced—His teachings to others, including the believers reading John's letter many years later.

This message begins with the idea that God is entirely goodness and truth, with no evil or falsehood. This is phrased in terms of light and darkness, common themes in the New Testament. As in verse 1, John alludes both to the creation account in Genesis chapters 1 and 2 and the introduction to his own Gospel in John chapter 1. God's first recorded words are, "Let there be light" (Genesis 1:3). John 1:4–5 records, "In him was life, and the life was the light of men. The light shines in the darkness, and the darkness has not overcome it."

Here in 1 John 1:5, John adds that God is light. He is without any darkness or shadow. He is both perfect and without sin.