Isaiah was the pessimistic prophet with the messianic hope. His sermons were dark clouds of gloom and doom, but they contained a silver lining and a golden promise. One day, he prophesied, a child would change everything.
John’s Gospel is full of light, but shadows linger. For every disciple there are more Pharisees. For every miracle, there are multitudes who remain unmoved. For every offer of free grace, there is an unyielding majority who remain steadfastly in slavery to sin. It is sad but true; the most common response to the gospel of belief, is unbelief.
Remember John writes in recurring themes. Jesus the Son of God, God incarnate, Lord. Jesus is the Son of Man, the promised Messiah, Savior. Saving faith is the goal of the Gospel (ref. 20:21).