Answer: John said that this book was "written that you may believe that Jesus is the Christ, the Son of God." John said that by this belief, which you may obtain by reading the Truths of this book, you may have life in the Name of Jesus, (verse 31).
MORE INFORMATION AND/OR OTHER SCRIPTURE REFERENCES:
"But these are written that you may believe..."
John 3:14-15: [Jesus said,] "Just as Moses lifted up the snake in the desert, so the Son of Man must be lifted up, that everyone who believes in Him may have eternal life."
John 19:35: "The man who saw it has given testimony, and his testimony is true. He knows that he tells the Truth, and he testifies so that you also may believe."
"...that Jesus is the Christ, the Son of God..."
Matthew 26:59-64: "The chief priests and the whole Sanhedrin were looking for false evidence against Jesus so that they could put Him to death. But they did not find any, though many false witnesses came forward. Finally two came forward and declared, ‘This fellow said, "I am able to destroy the temple of God and rebuild it in three days." Then the high priest stood up and said to Jesus, ‘Are you not going to answer? What is this testimony that these men are bringing against you?' But Jesus remained silent. The high priest said to Him, ‘I charge You under oath by the living God: Tell us if You are the Christ, the Son of God.' ‘Yes, it is as you say,' Jesus replied. ‘But I say to all of you: In the future you will see the Son of Man sitting at the right hand of the Mighty One and coming on the clouds of heaven.'"
John 5:25: [Jesus said,] "I tell you the Truth, a time is coming and has now come when the dead will hear the voice of the Son of God and those who hear will live."
"...and that by believing, you may have life in His Name."
John 6:66-69: "From this time many of His disciples turned back and no longer followed Him. ‘You do not want to leave too, do you?' Jesus asked the Twelve. Simon Peter answered Him, ‘Lord, to whom shall we go? You have the Words of eternal life. We believe and know that You are the Holy One of God.'"
Acts 4:10b-12: "It is by the Name of Jesus Christ of Nazareth, Whom you crucified but Whom God raised from the dead, that this man stands before you healed. He [Jesus] is ‘the stone you builders rejected, which has become the capstone.' Salvation is found in no one else, for there is no other name under heaven given to men by which we must be saved."
1 John 5:20: "We know also that the Son of God has come and has given us understanding, so that we may know Him Who is True. And we are in Him Who is True--even in His Son Jesus Christ. He is the True God and Eternal Life."
