How do we know that the testimony of John is true?

John's assertion of certainty regarding his testimony stems from his direct experience with Jesus Christ. He was one of Jesus' closest disciples, as noted within the Gospels, and he handled the Word of Life. This personal encounter provides a solid foundation for his claims. In John 21:24, he states, 'This is the disciple which testifies of these things, and wrote these things, and we know that his testimony is true.' Such testimony is reliable because it is divinely inspired and backed by his life as a martyr for the faith, indicating his profound commitment to the truths he declared.