Contradiction with John 3:18
John 1:7 speaks of bearing witness to the light for all to believe, but John 3:18 states that those who do not believe are condemned already.
John 3:18: He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
Contradiction with John 8:12
John 1:7 indicates that people need the witness to believe in the light, yet John 8:12 claims those who follow Jesus will not walk in darkness, implying immediate understanding.
John 8:12: Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life.
Contradiction with John 12:37-40
John 1:7 suggests belief through witness, but John 12:37-40 acknowledges some won't believe despite seeing many miracles.
John 12:37-40: But though he had done so many miracles before them, yet they believed not on him:
Contradiction with Romans 11:7-8
John 1:7 promotes belief through witnessing the light; however, Romans 11:7-8 notes that some were blinded and could not see or understand.
Romans 11:7-8: What then? Israel hath not obtained that which he seeketh for; but the election hath obtained it, and the rest were blinded [blinded: or, hardened]
Contradiction with 2 Corinthians 4:3-4
John 1:7 implies testimony will lead to belief in the light, yet 2 Corinthians 4:3-4 acknowledges the gospel can be hidden to those who are perishing.
2 Corinthians 4:3-4: But if our gospel be hid, it is hid to them that are lost: