The Gospel is supported by at least 4 written testimonies: Matthew, Mark, Luke and John as well as oral witnesses of many disciples of Jesus which forms the foundation of Christianity. There would not have been around 2 billion Christians today if the early disciples did not spread this Gospel.

1. If the disciples preached the Gospel for popularity or gain, they would not have included incidents which makes them look bad, for example:
   • Jesus correcting the mistakes of Peter (Mark 8:31-33), Thomas (John 14:5-7), James and John (Mark 10:35-45), the mother of James and John (Matthew 20:20-28)
   • Arguments among all the disciples (Luke 22:24-27)
   • All the disciples' lack of faith (Matthew 14:22-33)
   • Some disciples' failure to heal a demon-possessed boy (Mark 9:14-29)
   • All the disciples abandoning Jesus in a crisis (Mark 14:50-52; Matthew 26:56)
   • Peter's denial (Luke 22:54-62)
2. The very same disciples who wrote these books, initially fled and denied Jesus in the face of persecution (Matthew 26:56; Mark 14:50-52; Luke 22:54-62; John 18:15-18). From this we know that they are human and that they were not masochist. However, for the sake of the Gospel, to proof that it is true, it was important enough to them to go through with the persecution, for example:
   • Matthew was possibly stabbed to death according to the apocryphal text, "Martyrdom of Matthew".
   • Mark was burned to death after being dragged by horses through the streets of Alexandria, according to the apocryphal text, "Martyrdom of Mark".
   • Luke was hanged on an olive tree according to the apocryphal text, "Acts of Peter"
   • John was boiled alive in oil, but miraculously survived according to the apocryphal text, "Acts of John"
3. Jesus prophecies came true:
   • Jesus predicted his betrayal, suffering, and death at the hands of the authorities (Matthew 26:24)
   • Jesus foretold his resurrection after three days (Matthew 16:21)
   • Jesus prophesied the destruction of the Jerusalem temple by the Roman army (Matthew 24:1-2; Mark 13:1-2); Some scholars belief Matthew and Mark were written around 50 AD and the event only took place 70 AD
   • Jesus prophesied that his Gospel will be preached throughout the world (Matthew 24:14)
4. Early Christian writings support the Gospel like:
   • The letters of Paul
   • Hebrews
   • James
   • Peter
   • John
   • Jude
   • The Revelation from John of Patmos
5. Roman historians support the events of the Gospel:
   • Tacitus: In his "Annals", he mentions the execution of Jesus by Pontius Pilate and the existence of early Christians in Rome.
   • Suetonius: In his "Lives of the Twelve Caesars," he briefly mentions Christus, likely referring to Jesus, and the persecution of his followers under Claudius.
6. Jewish historian support the events of the Gospel:
   • Josephus: In his "Antiquities of the Jews," he mentions James, the brother of Jesus, and his execution by the Jewish high priest Ananus. While not directly referencing Jesus, this account confirms the existence of Jesus' brother and the potential for conflict between early Christians and Jewish authorities, as alluded to in the Gospels.
7. Archaeological evidence:
   • Discoveries in Judea and Galilee, including the Pool of Bethesda, the ruins of Capernaum, and the Second Temple in Jerusalem, offer archaeological context for the locations and settings mentioned in the Gospels. These findings, while not directly proving the Gospels' narratives, demonstrate the historical reality of the places and contexts described.
8. People that gets converted by the Gospel, is supposed to change (Romans 6:4; 2 Corinthians 5:17) so that they
   • live according to a new lifestyle (Galatians 5:19-24) led by God's Spirit;
   • live in peace with God (Matthew 3:15; 1 Peter 3:21)
9. Believers in the Gospel of Jesus the Christ, have access to God's power...

And these signs will accompany those who believe:

• in my [Jesus] name [authority] they will cast out demons;
• they will speak in new tongues;
• they will pick up serpents with their hands; and
• if they drink any deadly poison, it will not hurt them;
• they will lay their hands fon the sick, and they will recover.”

-- Mark 16:17-18

Questionable chapters

John 21

Some reason that John 21 is an addition which was not originally written by John, because:

• Some believe the language and style differs.
• John 20 concludes the witness of Jesus, but John 21 jumps back to another resurrection occurrence which breaks the text's chronological flow.
• John 21 refers to John in the third person.

Although some manuscripts lack John 21, some of the most early manuscripts did include John 21.

A possible explanation is that John as a fisherman was likely illiterate and someone else wrote the Gospel on his behalf and possibly added his own commentary at the end which some might have removed or included depending on the view of the person that copied the text.