What does John 9:40 mean?

According to Jesus' prior statement, those who are willfully ignorant of spiritual matters claim they have knowledge—"sight"—when in reality they're spiritually blind. A major component of Jesus' conflicts with religious leaders was their arrogance. Too often, these men started from the assumption that they knew best, and Jesus could not be true, simply because He didn't agree with them. As Jesus pointed out, that wasn't because God had failed to provide evidence (John 5:36). It was because these men refused to accept the truth (John 5:39–40).

As part of their debate against Jesus, the Pharisees now ask a pointed question. This is meant to be rhetorical—they ask with the assumption that the answer is an obvious "no." By their own standards, the Pharisees were the most moral, well-educated, and spiritually capable of men. One can imagine a modern Pharisee asking, sarcastically, "you're not saying I don't understand spirituality!" and laughing.

Jesus' response, in the next verse, shows that this is exactly the case. Worse, for the Pharisees, is their arrogance and presumption. Those who recognize their weakness and need for truth find forgiveness and grace (John 9:35–38; Mark 9:24). Those who claim they have knowledge will be judged according to their own standards (John 9:41).