What does John 7:17 mean?

The phrasing used here by Jesus is unmistakable; He literally says, "If any man is willing to do His (God's) will, he shall know…" While Satan tempts man with limited knowledge based in disobedience (Genesis 3:5), we are meant to obtain true knowledge through obedience. Jesus essentially turns His era's assumed relationship between knowledge and morality backwards. Ancient philosophers frequently held that morality was something produced by knowledge. Under that assumption, moral behavior and the ability to do "good" was based on whether or not a person understood moral and philosophical truths. Only those who could understand could obey, they thought. In other words, misunderstanding causes disobedience, per ancient philosophy.

According to Christ, disobedience causes misunderstanding. Rather than knowledge of the truth leading to obedience, Jesus claims that whether or not a person is willing to obey God is what affects their ability to learn the truth!

This general idea is echoed elsewhere in Scripture, both by Jesus and others (John 18:37; Romans 1:18–20; Hebrews 11:6). In fact, Jesus laid the groundwork for this idea when preaching in Capernaum, after feeding the thousands (John 6:29). The fact that Jesus was noted to be sinless (Hebrews 4:15), even by many of His own critics (John 8:46), demonstrates how a person's spiritual life says a great deal about their knowledge (or ignorance) of God's Word.