John 5:31-47 continues the words of Jesus to the Jews defending his strong claims that he was the Son of God, by referring to the testimony of many witnesses. Among those he mentioned included the testimony of John the Baptist, the words of God the Father, the writings of Moses and his own miraculous signs. These all agree and testify to the truth he proclaimed about himself.  It is not a lack of evidence that keeps people from believing, but a hardness of heart.