What does John 5:47 mean?

There are times when critics of the Bible will make an appeal to proof, especially in the form of a miracle. "If God would only 'prove' Himself, I would believe," these skeptics say. Typically, this means by some personal, custom miracle. In this verse, Jesus finishes a complete demolition of this claim. The Bible never calls on us to express blind faith—in this passage Christ has given three lines of evidence supporting His ministry. The problem is not in the evidence we have, but in whether or not we are willing to accept conclusions we don't like.

In the case of the local Jewish religious leaders, they simply refused to believe in Christ (John 5:39–40). Evidence is meaningless to those who willfully resist the truth. According to the Bible, every single person is given enough evidence that they have no excuse for not seeking God (Romans 1:18–22). Those who won't seek God in an honest, open way aren't going to believe the truth, regardless of what they may say.

This verse expresses the same point as the story of the rich man and Lazarus from Luke 16:19–31. There, Jesus made the point that those who reject the written Word of God aren't going to accept anything. Even when shown a miracle, even when seeing a resurrection, they will find some excuse to turn it away.

This is human nature. Israel witnessed God's miracles first-hand, but still disobeyed (Numbers 14:20–23; Nehemiah 9:16–17; Psalm 78:11–12). Thomas doubted despite his own experiences and the testimony of his friends (John 20:24–29). Judas was a personal friend of Jesus, but rejected Him (Matthew 26:24–25). Simply knowing is not the same as trusting, and knowledge is not the same as faith (James 2:19).

Those who reject the Son of God, ultimately, will have no excuse for their disbelief. They do not believe because they will not believe.