In five short chapters of 1 John, the word “know” or one of its derivatives is found thirty-eight times. Indeed, the concept of knowledge was extremely important to the apostle of love, as he dealt with the Gnostics and their claim to superior knowledge. Their claims were heartbreaking and concerning to the first-century church. No doubt it was a threat to their faith. So, John wanted his readers to have a complete and firm conviction. He wanted them to know that they knew that they knew the truth, and be able to distinguish it from error. This confidence was critical for the church in the first century, as it is for you and me today.
One of the many passages in the book that reference knowledge is 1 John 5:13. John says,
These things I have written unto you who believe in the name of the Son of God; that you may know that you have eternal life, and that you may continue to believe on the name of the Son of God.
This, along with 1 John 1:4 and 2:1, is one of the three purpose passages of the book. Of the phrase “that you may know,” Marvin Vincent said, “not perceive, but know with settled and absolute knowledge” (c.f. John 2:24). God wants us to have “settled and absolute knowledge” that we have eternal life. But, how is this possible. By combining the thoughts of 1 John 1:4; 2:1; and 5:13 we have a clear and practical answer.
In 1 John 2:1 John wrote, “My little children, these things I write to you, so that you may sin…” John did not want his readers to view sin as a normal or acceptable way of life. Instead, he wanted them to avoid it at all costs. Paul’s question in Romans 6:1-2 comes to mind, “Shall we continue in sin that grace may abound? Certainly not! How shall we who died to sin, live any longer in it?” But, how can we be sure to avoid sin? John has already told us in 1 John 1:7
But if we walk in the light, as He is in the light, we have fellowship with one another, and the blood of Jesus Christ his Son cleanses us from all sin.
To “walk in the light” is to live a life of faithful obedience to the will of God. So, if I am walking in the light, I will avoid living in sin because God directs my conduct through His word.
The purpose passage that summarizes the point is 1 John 1:4 where John wrote, “And these things we write to you, that your joy may be full.” God never has intended for His people to wander aimlessly through life with no hope and no confidence that they are pleasing Him, or preparing themselves to be with Him in eternity. John referenced this in 1 John 3:19 when he said, “And by this, we know that we are of the truth, and shall assure our hearts before him.” We “know that we are of the truth” and we know that we have eternal life by knowing that we are faithfully obeying our Father. This confidence produces joy. Peter referred to it as “joy inexpressible and full of glory” (1 Pet. 1:8). Paul said, “and the peace of God which surpasses all understanding will guard your hearts and minds through Christ Jesus” (Phil. 4:7). My joy is full and overflowing when I know that Heaven will be a reality for me because I am faithful to the Father. If I walk in the light (1 John 1:7) I will abstain from sin (1 John 2:2). If I abstain from sin (1 John 2:2) I can know that I have eternal life (1 John 5:13). And, when I know that I have eternal life (1 John 5:13) my joy is full (1 John 1:4).