Considering the Gospel of John, Leon Morris wrote that it is a pool in which a child can wade and an elephant can swim. It is both simple and profound. Its stories are so simple that even a child will love them, but its statements are so profound that no philosopher can fathom them.
This Gospel presents Jesus as the Son of God who became man and then revealed the truth about God to humankind. Jesus is often referred to as the God-man. In His dual nature, He is both 100% God and 100% man. The emphasis in this Gospel is more strongly on Jesus’ full deity.
This Gospel has an especially strong appeal to non-Christians. John wrote it specifically to bring understanding about Jesus’ true identity to those who sit in spiritual darkness. The knowledge of who Jesus really is, is the key to the knowledge of who God really is. There is no better way for non-Christians to understand who Jesus is than by reading this Gospel. The stated purpose of this book is: “Jesus did many other miraculous signs in the presence of his disciples, which are not recorded in this book. But these are written that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name” John 20:30-31.
The key word in the book is the verb “believe” (Gr. pisteuo), which appears 98 times. The noun form of the word (Gr. pistis, “faith”) does not occur at all. This phenomenon shows that John wanted to emphasize the importance of active, vital trust in Jesus. John’s repeated emphasis is on salvation by faith (belief) alone.
Charles Erdman says that the Gospel of John “has induced more persons to follow Christ, it has inspired more believers to loyal service, and it has presented to scholars more difficult problems than any other book that could be named.”