John 20:31
John 20:3131But these are written so that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in His name.
The Watchtower cites ("these have been written so that you may believe that Jesus is the Christ, the Son of God") to argue that John's purpose is to establish Jesus as the Messiah and the Son of God — not as God himself. The title "Son of God" is read as indicating a subordinate relationship: the Son is less than the Father, just as a human son is distinct from his father. On this reading, the Gospel of John proves that Jesus is a uniquely exalted creature — the firstborn of creation — who holds the title "Son" precisely because he is not the Father and not equal to God. The verse is deployed as the interpretive key that should govern all other Johannine passages, including and .
Protestants read as the capstone of the entire Gospel — the verse that tells the reader why John wrote everything that precedes it. Crucially, this statement comes immediately after Thomas's confession in , where Thomas addresses Jesus directly as "my Lord and my God" (ho kurios mou kai ho theos mou). Jesus does not correct Thomas; he commends his faith. John then writes that these things were recorded "so that you may believe" — meaning the belief John is aiming for is the very belief Thomas has just expressed. "Son of God" in John's Gospel is not a subordination title; says the Jews sought to kill Jesus because he was "calling God his own Father, making himself equal with God." The title carries the weight of shared divine nature, not lesser rank. The argument from ("you have the words of eternal life") reinforces this: Peter's confession, like Thomas's, is directed to Jesus personally, and explains that the entire Gospel was written to bring every reader to that same personal confession.